Merge branch 'rust/cpufreq-dt' into cpufreq/arm/linux-next

MAINTAINERS

···
 F:	include/linux/clk-pr*
 F:	include/linux/clk/
 F:	include/linux/of_clk.h
+F:	rust/helpers/clk.c
+F:	rust/kernel/clk.rs
 X:	drivers/clk/clkdev.c
 
 COMMON INTERNET FILE SYSTEM CLIENT (CIFS and SMB3)
···
 F:	include/linux/cpufreq.h
 F:	include/linux/sched/cpufreq.h
 F:	kernel/sched/cpufreq*.c
+F:	rust/kernel/cpufreq.rs
 F:	tools/testing/selftests/cpufreq/
 
 CPU HOTPLUG
···
 F:	include/linux/smpboot.h
 F:	kernel/cpu.c
 F:	kernel/smpboot.*
+F:	rust/kernel/cpu.rs
 
 CPU IDLE TIME MANAGEMENT FRAMEWORK
 M:	"Rafael J. Wysocki" <[e-mail]>
···
 L:	[e-mail]
 S:	Maintained
 F:	drivers/cpuidle/cpuidle-riscv-sbi.c
+
+CPUMASK API [RUST]
+M:	Viresh Kumar <[e-mail]>
+R:	Yury Norov <[e-mail]>
+S:	Maintained
+F:	rust/kernel/cpumask.rs
 
 CRAMFS FILESYSTEM
 M:	Nicolas Pitre <[e-mail]>
···
 F:	Documentation/power/opp.rst
 F:	drivers/opp/
 F:	include/linux/pm_opp.h
+F:	rust/kernel/opp.rs
 
 OPL4 DRIVER
 M:	Clemens Ladisch <[e-mail]>

drivers/cpufreq/Kconfig

···
 
 	  If in doubt, say N.
 
+config CPUFREQ_DT_RUST
+	tristate "Rust based Generic DT based cpufreq driver"
+	depends on HAVE_CLK && OF && RUST
+	select CPUFREQ_DT_PLATDEV
+	select PM_OPP
+	help
+	  This adds a Rust based generic DT based cpufreq driver for frequency
+	  management.  It supports both uniprocessor (UP) and symmetric
+	  multiprocessor (SMP) systems.
+
+	  If in doubt, say N.
+
 config CPUFREQ_VIRT
 	tristate "Virtual cpufreq driver"
 	depends on GENERIC_ARCH_TOPOLOGY

drivers/cpufreq/Makefile

···
 obj-$(CONFIG_CPU_FREQ_GOV_ATTR_SET)	+= cpufreq_governor_attr_set.o
 
 obj-$(CONFIG_CPUFREQ_DT)		+= cpufreq-dt.o
+obj-$(CONFIG_CPUFREQ_DT_RUST)		+= rcpufreq_dt.o
 obj-$(CONFIG_CPUFREQ_DT_PLATDEV)	+= cpufreq-dt-platdev.o
 obj-$(CONFIG_CPUFREQ_VIRT)		+= virtual-cpufreq.o
 

drivers/cpufreq/amd-pstate.c

···
 	schedule_work(&sched_prefcore_work);
 }
 
-static void amd_pstate_update_limits(unsigned int cpu)
+static void amd_pstate_update_limits(struct cpufreq_policy *policy)
 {
-	struct cpufreq_policy *policy __free(put_cpufreq_policy) = cpufreq_cpu_get(cpu);
 	struct amd_cpudata *cpudata;
 	u32 prev_high = 0, cur_high = 0;
 	bool highest_perf_changed = false;
+	unsigned int cpu = policy->cpu;
 
 	if (!amd_pstate_prefcore)
-		return;
-
-	if (!policy)
 		return;
 
 	if (amd_get_highest_perf(cpu, &cur_high))

drivers/cpufreq/cpufreq.c

···
 }
 EXPORT_SYMBOL_GPL(cpufreq_cpu_put);
 
-/**
- * cpufreq_cpu_release - Unlock a policy and decrement its usage counter.
- * @policy: cpufreq policy returned by cpufreq_cpu_acquire().
- */
-void cpufreq_cpu_release(struct cpufreq_policy *policy)
-{
-	if (WARN_ON(!policy))
-		return;
-
-	lockdep_assert_held(&policy->rwsem);
-
-	up_write(&policy->rwsem);
-
-	cpufreq_cpu_put(policy);
-}
-
-/**
- * cpufreq_cpu_acquire - Find policy for a CPU, mark it as busy and lock it.
- * @cpu: CPU to find the policy for.
- *
- * Call cpufreq_cpu_get() to get a reference on the cpufreq policy for @cpu and
- * if the policy returned by it is not NULL, acquire its rwsem for writing.
- * Return the policy if it is active or release it and return NULL otherwise.
- *
- * The policy returned by this function has to be released with the help of
- * cpufreq_cpu_release() in order to release its rwsem and balance its usage
- * counter properly.
- */
-struct cpufreq_policy *cpufreq_cpu_acquire(unsigned int cpu)
-{
-	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
-
-	if (!policy)
-		return NULL;
-
-	down_write(&policy->rwsem);
-
-	if (policy_is_inactive(policy)) {
-		cpufreq_cpu_release(policy);
-		return NULL;
-	}
-
-	return policy;
-}
-
 /*********************************************************************
  *            EXTERNALLY AFFECTING FREQUENCY CHANGES                 *
  *********************************************************************/
···
 {
 	struct cpufreq_policy *policy = to_policy(kobj);
 	struct freq_attr *fattr = to_attr(attr);
-	ssize_t ret = -EBUSY;
 
 	if (!fattr->show)
 		return -EIO;
 
-	down_read(&policy->rwsem);
-	if (likely(!policy_is_inactive(policy)))
-		ret = fattr->show(policy, buf);
-	up_read(&policy->rwsem);
+	guard(cpufreq_policy_read)(policy);
 
-	return ret;
+	if (likely(!policy_is_inactive(policy)))
+		return fattr->show(policy, buf);
+
+	return -EBUSY;
 }
 
 static ssize_t store(struct kobject *kobj, struct attribute *attr,
···
 {
 	struct cpufreq_policy *policy = to_policy(kobj);
 	struct freq_attr *fattr = to_attr(attr);
-	ssize_t ret = -EBUSY;
 
 	if (!fattr->store)
 		return -EIO;
 
-	down_write(&policy->rwsem);
-	if (likely(!policy_is_inactive(policy)))
-		ret = fattr->store(policy, buf, count);
-	up_write(&policy->rwsem);
+	guard(cpufreq_policy_write)(policy);
 
-	return ret;
+	if (likely(!policy_is_inactive(policy)))
+		return fattr->store(policy, buf, count);
+
+	return -EBUSY;
 }
 
 static void cpufreq_sysfs_release(struct kobject *kobj)
···
 	if (cpumask_test_cpu(cpu, policy->cpus))
 		return 0;
 
-	down_write(&policy->rwsem);
+	guard(cpufreq_policy_write)(policy);
+
 	if (has_target())
 		cpufreq_stop_governor(policy);
 
···
 		if (ret)
 			pr_err("%s: Failed to start governor\n", __func__);
 	}
-	up_write(&policy->rwsem);
+
 	return ret;
 }
 
···
 		container_of(work, struct cpufreq_policy, update);
 
 	pr_debug("handle_update for cpu %u called\n", policy->cpu);
-	down_write(&policy->rwsem);
+
+	guard(cpufreq_policy_write)(policy);
+
 	refresh_frequency_limits(policy);
-	up_write(&policy->rwsem);
 }
 
 static int cpufreq_notifier_min(struct notifier_block *nb, unsigned long freq,
···
 	struct kobject *kobj;
 	struct completion *cmp;
 
-	down_write(&policy->rwsem);
-	cpufreq_stats_free_table(policy);
-	kobj = &policy->kobj;
-	cmp = &policy->kobj_unregister;
-	up_write(&policy->rwsem);
+	scoped_guard(cpufreq_policy_write, policy) {
+		cpufreq_stats_free_table(policy);
+		kobj = &policy->kobj;
+		cmp = &policy->kobj_unregister;
+	}
 	kobject_put(kobj);
 
 	/*
···
 	init_waitqueue_head(&policy->transition_wait);
 	INIT_WORK(&policy->update, handle_update);
 
-	policy->cpu = cpu;
 	return policy;
 
 err_min_qos_notifier:
···
 	kfree(policy);
 }
 
-static int cpufreq_online(unsigned int cpu)
+static int cpufreq_policy_online(struct cpufreq_policy *policy,
+				 unsigned int cpu, bool new_policy)
 {
-	struct cpufreq_policy *policy;
-	bool new_policy;
 	unsigned long flags;
 	unsigned int j;
 	int ret;
 
-	pr_debug("%s: bringing CPU%u online\n", __func__, cpu);
+	guard(cpufreq_policy_write)(policy);
 
-	/* Check if this CPU already has a policy to manage it */
-	policy = per_cpu(cpufreq_cpu_data, cpu);
-	if (policy) {
-		WARN_ON(!cpumask_test_cpu(cpu, policy->related_cpus));
-		if (!policy_is_inactive(policy))
-			return cpufreq_add_policy_cpu(policy, cpu);
-
-		/* This is the only online CPU for the policy.  Start over. */
-		new_policy = false;
-		down_write(&policy->rwsem);
-		policy->cpu = cpu;
-		policy->governor = NULL;
-	} else {
-		new_policy = true;
-		policy = cpufreq_policy_alloc(cpu);
-		if (!policy)
-			return -ENOMEM;
-		down_write(&policy->rwsem);
-	}
+	policy->cpu = cpu;
+	policy->governor = NULL;
 
 	if (!new_policy && cpufreq_driver->online) {
 		/* Recover policy->cpus using related_cpus */
···
 		if (ret) {
 			pr_debug("%s: %d: initialization failed\n", __func__,
 				 __LINE__);
-			goto out_free_policy;
+			goto out_clear_policy;
 		}
 
 		/*
···
 		goto out_destroy_policy;
 	}
 
-	up_write(&policy->rwsem);
+	return 0;
+
+out_destroy_policy:
+	for_each_cpu(j, policy->real_cpus)
+		remove_cpu_dev_symlink(policy, j, get_cpu_device(j));
+
+out_offline_policy:
+	if (cpufreq_driver->offline)
+		cpufreq_driver->offline(policy);
+
+out_exit_policy:
+	if (cpufreq_driver->exit)
+		cpufreq_driver->exit(policy);
+
+out_clear_policy:
+	cpumask_clear(policy->cpus);
+
+	return ret;
+}
+
+static int cpufreq_online(unsigned int cpu)
+{
+	struct cpufreq_policy *policy;
+	bool new_policy;
+	int ret;
+
+	pr_debug("%s: bringing CPU%u online\n", __func__, cpu);
+
+	/* Check if this CPU already has a policy to manage it */
+	policy = per_cpu(cpufreq_cpu_data, cpu);
+	if (policy) {
+		WARN_ON(!cpumask_test_cpu(cpu, policy->related_cpus));
+		if (!policy_is_inactive(policy))
+			return cpufreq_add_policy_cpu(policy, cpu);
+
+		/* This is the only online CPU for the policy.  Start over. */
+		new_policy = false;
+	} else {
+		new_policy = true;
+		policy = cpufreq_policy_alloc(cpu);
+		if (!policy)
+			return -ENOMEM;
+	}
+
+	ret = cpufreq_policy_online(policy, cpu, new_policy);
+	if (ret) {
+		cpufreq_policy_free(policy);
+		return ret;
+	}
 
 	kobject_uevent(&policy->kobj, KOBJ_ADD);
 
···
 	pr_debug("initialization complete\n");
 
 	return 0;
-
-out_destroy_policy:
-	for_each_cpu(j, policy->real_cpus)
-		remove_cpu_dev_symlink(policy, j, get_cpu_device(j));
-
-out_offline_policy:
-	if (cpufreq_driver->offline)
-		cpufreq_driver->offline(policy);
-
-out_exit_policy:
-	if (cpufreq_driver->exit)
-		cpufreq_driver->exit(policy);
-
-out_free_policy:
-	cpumask_clear(policy->cpus);
-	up_write(&policy->rwsem);
-
-	cpufreq_policy_free(policy);
-	return ret;
 }
 
 /**
···
 		return 0;
 	}
 
-	down_write(&policy->rwsem);
+	guard(cpufreq_policy_write)(policy);
 
 	__cpufreq_offline(cpu, policy);
 
-	up_write(&policy->rwsem);
 	return 0;
 }
 
···
 	if (!policy)
 		return;
 
-	down_write(&policy->rwsem);
+	scoped_guard(cpufreq_policy_write, policy) {
+		if (cpu_online(cpu))
+			__cpufreq_offline(cpu, policy);
 
-	if (cpu_online(cpu))
-		__cpufreq_offline(cpu, policy);
+		remove_cpu_dev_symlink(policy, cpu, dev);
 
-	remove_cpu_dev_symlink(policy, cpu, dev);
+		if (!cpumask_empty(policy->real_cpus))
+			return;
 
-	if (!cpumask_empty(policy->real_cpus)) {
-		up_write(&policy->rwsem);
-		return;
+		/*
+		 * Unregister cpufreq cooling once all the CPUs of the policy
+		 * are removed.
+		 */
+		if (cpufreq_thermal_control_enabled(cpufreq_driver)) {
+			cpufreq_cooling_unregister(policy->cdev);
+			policy->cdev = NULL;
+		}
+
+		/* We did light-weight exit earlier, do full tear down now */
+		if (cpufreq_driver->offline && cpufreq_driver->exit)
+			cpufreq_driver->exit(policy);
 	}
-
-	/*
-	 * Unregister cpufreq cooling once all the CPUs of the policy are
-	 * removed.
-	 */
-	if (cpufreq_thermal_control_enabled(cpufreq_driver)) {
-		cpufreq_cooling_unregister(policy->cdev);
-		policy->cdev = NULL;
-	}
-
-	/* We did light-weight exit earlier, do full tear down now */
-	if (cpufreq_driver->offline && cpufreq_driver->exit)
-		cpufreq_driver->exit(policy);
-
-	up_write(&policy->rwsem);
 
 	cpufreq_policy_free(policy);
 }
···
  */
 unsigned int cpufreq_quick_get(unsigned int cpu)
 {
-	struct cpufreq_policy *policy;
-	unsigned int ret_freq = 0;
+	struct cpufreq_policy *policy __free(put_cpufreq_policy) = NULL;
 	unsigned long flags;
 
 	read_lock_irqsave(&cpufreq_driver_lock, flags);
 
 	if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get) {
-		ret_freq = cpufreq_driver->get(cpu);
+		unsigned int ret_freq = cpufreq_driver->get(cpu);
+
 		read_unlock_irqrestore(&cpufreq_driver_lock, flags);
+
 		return ret_freq;
 	}
 
 	read_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
 	policy = cpufreq_cpu_get(cpu);
-	if (policy) {
-		ret_freq = policy->cur;
-		cpufreq_cpu_put(policy);
-	}
+	if (policy)
+		return policy->cur;
 
-	return ret_freq;
+	return 0;
 }
 EXPORT_SYMBOL(cpufreq_quick_get);
 
···
  */
 unsigned int cpufreq_quick_get_max(unsigned int cpu)
 {
-	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
-	unsigned int ret_freq = 0;
+	struct cpufreq_policy *policy __free(put_cpufreq_policy);
 
-	if (policy) {
-		ret_freq = policy->max;
-		cpufreq_cpu_put(policy);
-	}
+	policy = cpufreq_cpu_get(cpu);
+	if (policy)
+		return policy->max;
 
-	return ret_freq;
+	return 0;
 }
 EXPORT_SYMBOL(cpufreq_quick_get_max);
 
···
  */
 __weak unsigned int cpufreq_get_hw_max_freq(unsigned int cpu)
 {
-	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
-	unsigned int ret_freq = 0;
+	struct cpufreq_policy *policy __free(put_cpufreq_policy);
 
-	if (policy) {
-		ret_freq = policy->cpuinfo.max_freq;
-		cpufreq_cpu_put(policy);
-	}
+	policy = cpufreq_cpu_get(cpu);
+	if (policy)
+		return policy->cpuinfo.max_freq;
 
-	return ret_freq;
+	return 0;
 }
 EXPORT_SYMBOL(cpufreq_get_hw_max_freq);
 
···
  */
 unsigned int cpufreq_get(unsigned int cpu)
 {
-	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
-	unsigned int ret_freq = 0;
+	struct cpufreq_policy *policy __free(put_cpufreq_policy);
 
-	if (policy) {
-		down_read(&policy->rwsem);
-		if (cpufreq_driver->get)
-			ret_freq = __cpufreq_get(policy);
-		up_read(&policy->rwsem);
+	policy = cpufreq_cpu_get(cpu);
+	if (!policy)
+		return 0;
 
-		cpufreq_cpu_put(policy);
-	}
+	guard(cpufreq_policy_read)(policy);
 
-	return ret_freq;
+	if (cpufreq_driver->get)
+		return __cpufreq_get(policy);
+
+	return 0;
 }
 EXPORT_SYMBOL(cpufreq_get);
 
···
 
 	for_each_active_policy(policy) {
 		if (has_target()) {
-			down_write(&policy->rwsem);
-			cpufreq_stop_governor(policy);
-			up_write(&policy->rwsem);
+			scoped_guard(cpufreq_policy_write, policy) {
+				cpufreq_stop_governor(policy);
+			}
 		}
 
 		if (cpufreq_driver->suspend && cpufreq_driver->suspend(policy))
···
 			pr_err("%s: Failed to resume driver: %s\n", __func__,
 				cpufreq_driver->name);
 		} else if (has_target()) {
-			down_write(&policy->rwsem);
-			ret = cpufreq_start_governor(policy);
-			up_write(&policy->rwsem);
+			scoped_guard(cpufreq_policy_write, policy) {
+				ret = cpufreq_start_governor(policy);
+			}
 
 			if (ret)
 				pr_err("%s: Failed to start governor for CPU%u's policy\n",
···
 			  unsigned int target_freq,
 			  unsigned int relation)
 {
-	int ret;
+	guard(cpufreq_policy_write)(policy);
 
-	down_write(&policy->rwsem);
-
-	ret = __cpufreq_driver_target(policy, target_freq, relation);
-
-	up_write(&policy->rwsem);
-
-	return ret;
+	return __cpufreq_driver_target(policy, target_freq, relation);
 }
 EXPORT_SYMBOL_GPL(cpufreq_driver_target);
 
···
  */
 int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu)
 {
-	struct cpufreq_policy *cpu_policy;
+	struct cpufreq_policy *cpu_policy __free(put_cpufreq_policy);
+
 	if (!policy)
 		return -EINVAL;
 
···
 
 	memcpy(policy, cpu_policy, sizeof(*policy));
 
-	cpufreq_cpu_put(cpu_policy);
 	return 0;
 }
 EXPORT_SYMBOL(cpufreq_get_policy);
···
 	return ret;
 }
 
+static void cpufreq_policy_refresh(struct cpufreq_policy *policy)
+{
+	guard(cpufreq_policy_write)(policy);
+
+	/*
+	 * BIOS might change freq behind our back
+	 * -> ask driver for current freq and notify governors about a change
+	 */
+	if (cpufreq_driver->get && has_target() &&
+	    (cpufreq_suspended || WARN_ON(!cpufreq_verify_current_freq(policy, false))))
+		return;
+
+	refresh_frequency_limits(policy);
+}
+
 /**
  * cpufreq_update_policy - Re-evaluate an existing cpufreq policy.
  * @cpu: CPU to re-evaluate the policy for.
···
  */
 void cpufreq_update_policy(unsigned int cpu)
 {
-	struct cpufreq_policy *policy = cpufreq_cpu_acquire(cpu);
+	struct cpufreq_policy *policy __free(put_cpufreq_policy);
 
+	policy = cpufreq_cpu_get(cpu);
 	if (!policy)
 		return;
 
-	/*
-	 * BIOS might change freq behind our back
-	 * -> ask driver for current freq and notify governors about a change
-	 */
-	if (cpufreq_driver->get && has_target() &&
-	    (cpufreq_suspended || WARN_ON(!cpufreq_verify_current_freq(policy, false))))
-		goto unlock;
-
-	refresh_frequency_limits(policy);
-
-unlock:
-	cpufreq_cpu_release(policy);
+	cpufreq_policy_refresh(policy);
 }
 EXPORT_SYMBOL(cpufreq_update_policy);
 
···
  * @cpu: CPU to update the policy limits for.
  *
  * Invoke the driver's ->update_limits callback if present or call
- * cpufreq_update_policy() for @cpu.
+ * cpufreq_policy_refresh() for @cpu.
  */
 void cpufreq_update_limits(unsigned int cpu)
 {
···
 		return;
 
 	if (cpufreq_driver->update_limits)
-		cpufreq_driver->update_limits(cpu);
+		cpufreq_driver->update_limits(policy);
 	else
-		cpufreq_update_policy(cpu);
+		cpufreq_policy_refresh(policy);
 }
 EXPORT_SYMBOL_GPL(cpufreq_update_limits);
 

drivers/cpufreq/intel_pstate.c

···
 		cpufreq_update_policy(cpu);
 }
 
-static void __intel_pstate_update_max_freq(struct cpudata *cpudata,
-					   struct cpufreq_policy *policy)
+static void __intel_pstate_update_max_freq(struct cpufreq_policy *policy,
+					   struct cpudata *cpudata)
 {
+	guard(cpufreq_policy_write)(policy);
+
 	if (hwp_active)
 		intel_pstate_get_hwp_cap(cpudata);
 
···
 	refresh_frequency_limits(policy);
 }
 
-static void intel_pstate_update_limits(unsigned int cpu)
+static bool intel_pstate_update_max_freq(struct cpudata *cpudata)
 {
-	struct cpufreq_policy *policy = cpufreq_cpu_acquire(cpu);
-	struct cpudata *cpudata;
+	struct cpufreq_policy *policy __free(put_cpufreq_policy);
 
+	policy = cpufreq_cpu_get(cpudata->cpu);
 	if (!policy)
-		return;
+		return false;
 
-	cpudata = all_cpu_data[cpu];
+	__intel_pstate_update_max_freq(policy, cpudata);
 
-	__intel_pstate_update_max_freq(cpudata, policy);
+	return true;
+}
 
-	/* Prevent the driver from being unregistered now. */
-	mutex_lock(&intel_pstate_driver_lock);
+static void intel_pstate_update_limits(struct cpufreq_policy *policy)
+{
+	struct cpudata *cpudata = all_cpu_data[policy->cpu];
 
-	cpufreq_cpu_release(policy);
+	__intel_pstate_update_max_freq(policy, cpudata);
 
 	hybrid_update_capacity(cpudata);
-
-	mutex_unlock(&intel_pstate_driver_lock);
 }
 
 static void intel_pstate_update_limits_for_all(void)
 {
 	int cpu;
 
-	for_each_possible_cpu(cpu) {
-		struct cpufreq_policy *policy = cpufreq_cpu_acquire(cpu);
-
-		if (!policy)
-			continue;
-
-		__intel_pstate_update_max_freq(all_cpu_data[cpu], policy);
-
-		cpufreq_cpu_release(policy);
-	}
+	for_each_possible_cpu(cpu)
+		intel_pstate_update_max_freq(all_cpu_data[cpu]);
 
 	mutex_lock(&hybrid_capacity_lock);
 
···
 {
 	struct cpudata *cpudata =
 		container_of(to_delayed_work(work), struct cpudata, hwp_notify_work);
-	struct cpufreq_policy *policy = cpufreq_cpu_acquire(cpudata->cpu);
 
-	if (policy) {
-		__intel_pstate_update_max_freq(cpudata, policy);
-
-		cpufreq_cpu_release(policy);
-
+	if (intel_pstate_update_max_freq(cpudata)) {
 		/*
 		 * The driver will not be unregistered while this function is
 		 * running, so update the capacity without acquiring the driver

drivers/cpufreq/rcpufreq_dt.rs

···
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust based implementation of the cpufreq-dt driver.
+
+use kernel::{
+    c_str,
+    clk::Clk,
+    cpu, cpufreq,
+    cpumask::CpumaskVar,
+    device::{Core, Device},
+    error::code::*,
+    fmt,
+    macros::vtable,
+    module_platform_driver, of, opp, platform,
+    prelude::*,
+    str::CString,
+    sync::Arc,
+};
+
+/// Finds exact supply name from the OF node.
+fn find_supply_name_exact(dev: &Device, name: &str) -> Option<CString> {
+    let prop_name = CString::try_from_fmt(fmt!("{}-supply", name)).ok()?;
+    dev.property_present(&prop_name)
+        .then(|| CString::try_from_fmt(fmt!("{name}")).ok())
+        .flatten()
+}
+
+/// Finds supply name for the CPU from DT.
+fn find_supply_names(dev: &Device, cpu: u32) -> Option<KVec<CString>> {
+    // Try "cpu0" for older DTs, fallback to "cpu".
+    let name = (cpu == 0)
+        .then(|| find_supply_name_exact(dev, "cpu0"))
+        .flatten()
+        .or_else(|| find_supply_name_exact(dev, "cpu"))?;
+
+    let mut list = KVec::with_capacity(1, GFP_KERNEL).ok()?;
+    list.push(name, GFP_KERNEL).ok()?;
+
+    Some(list)
+}
+
+/// Represents the cpufreq dt device.
+struct CPUFreqDTDevice {
+    opp_table: opp::Table,
+    freq_table: opp::FreqTable,
+    _mask: CpumaskVar,
+    _token: Option<opp::ConfigToken>,
+    _clk: Clk,
+}
+
+#[derive(Default)]
+struct CPUFreqDTDriver;
+
+#[vtable]
+impl opp::ConfigOps for CPUFreqDTDriver {}
+
+#[vtable]
+impl cpufreq::Driver for CPUFreqDTDriver {
+    const NAME: &'static CStr = c_str!("cpufreq-dt");
+    const FLAGS: u16 = cpufreq::flags::NEED_INITIAL_FREQ_CHECK | cpufreq::flags::IS_COOLING_DEV;
+    const BOOST_ENABLED: bool = true;
+
+    type PData = Arc<CPUFreqDTDevice>;
+
+    fn init(policy: &mut cpufreq::Policy) -> Result<Self::PData> {
+        let cpu = policy.cpu();
+        // SAFETY: The CPU device is only used during init; it won't get hot-unplugged. The cpufreq
+        // core  registers with CPU notifiers and the cpufreq core/driver won't use the CPU device,
+        // once the CPU is hot-unplugged.
+        let dev = unsafe { cpu::from_cpu(cpu)? };
+        let mut mask = CpumaskVar::new_zero(GFP_KERNEL)?;
+
+        mask.set(cpu);
+
+        let token = find_supply_names(dev, cpu)
+            .map(|names| {
+                opp::Config::<Self>::new()
+                    .set_regulator_names(names)?
+                    .set(dev)
+            })
+            .transpose()?;
+
+        // Get OPP-sharing information from "operating-points-v2" bindings.
+        let fallback = match opp::Table::of_sharing_cpus(dev, &mut mask) {
+            Ok(()) => false,
+            Err(e) if e == ENOENT => {
+                // "operating-points-v2" not supported. If the platform hasn't
+                // set sharing CPUs, fallback to all CPUs share the `Policy`
+                // for backward compatibility.
+                opp::Table::sharing_cpus(dev, &mut mask).is_err()
+            }
+            Err(e) => return Err(e),
+        };
+
+        // Initialize OPP tables for all policy cpus.
+        //
+        // For platforms not using "operating-points-v2" bindings, we do this
+        // before updating policy cpus. Otherwise, we will end up creating
+        // duplicate OPPs for the CPUs.
+        //
+        // OPPs might be populated at runtime, don't fail for error here unless
+        // it is -EPROBE_DEFER.
+        let mut opp_table = match opp::Table::from_of_cpumask(dev, &mut mask) {
+            Ok(table) => table,
+            Err(e) => {
+                if e == EPROBE_DEFER {
+                    return Err(e);
+                }
+
+                // The table is added dynamically ?
+                opp::Table::from_dev(dev)?
+            }
+        };
+
+        // The OPP table must be initialized, statically or dynamically, by this point.
+        opp_table.opp_count()?;
+
+        // Set sharing cpus for fallback scenario.
+        if fallback {
+            mask.setall();
+            opp_table.set_sharing_cpus(&mut mask)?;
+        }
+
+        let mut transition_latency = opp_table.max_transition_latency_ns() as u32;
+        if transition_latency == 0 {
+            transition_latency = cpufreq::ETERNAL_LATENCY_NS;
+        }
+
+        policy
+            .set_dvfs_possible_from_any_cpu(true)
+            .set_suspend_freq(opp_table.suspend_freq())
+            .set_transition_latency_ns(transition_latency);
+
+        let freq_table = opp_table.cpufreq_table()?;
+        // SAFETY: The `freq_table` is not dropped while it is getting used by the C code.
+        unsafe { policy.set_freq_table(&freq_table) };
+
+        // SAFETY: The returned `clk` is not dropped while it is getting used by the C code.
+        let clk = unsafe { policy.set_clk(dev, None)? };
+
+        mask.copy(policy.cpus());
+
+        Ok(Arc::new(
+            CPUFreqDTDevice {
+                opp_table,
+                freq_table,
+                _mask: mask,
+                _token: token,
+                _clk: clk,
+            },
+            GFP_KERNEL,
+        )?)
+    }
+
+    fn exit(_policy: &mut cpufreq::Policy, _data: Option<Self::PData>) -> Result {
+        Ok(())
+    }
+
+    fn online(_policy: &mut cpufreq::Policy) -> Result {
+        // We did light-weight tear down earlier, nothing to do here.
+        Ok(())
+    }
+
+    fn offline(_policy: &mut cpufreq::Policy) -> Result {
+        // Preserve policy->data and don't free resources on light-weight
+        // tear down.
+        Ok(())
+    }
+
+    fn suspend(policy: &mut cpufreq::Policy) -> Result {
+        policy.generic_suspend()
+    }
+
+    fn verify(data: &mut cpufreq::PolicyData) -> Result {
+        data.generic_verify()
+    }
+
+    fn target_index(policy: &mut cpufreq::Policy, index: cpufreq::TableIndex) -> Result {
+        let Some(data) = policy.data::<Self::PData>() else {
+            return Err(ENOENT);
+        };
+
+        let freq = data.freq_table.freq(index)?;
+        data.opp_table.set_rate(freq)
+    }
+
+    fn get(policy: &mut cpufreq::Policy) -> Result<u32> {
+        policy.generic_get()
+    }
+
+    fn set_boost(_policy: &mut cpufreq::Policy, _state: i32) -> Result {
+        Ok(())
+    }
+
+    fn register_em(policy: &mut cpufreq::Policy) {
+        policy.register_em_opp()
+    }
+}
+
+kernel::of_device_table!(
+    OF_TABLE,
+    MODULE_OF_TABLE,
+    <CPUFreqDTDriver as platform::Driver>::IdInfo,
+    [(of::DeviceId::new(c_str!("operating-points-v2")), ())]
+);
+
+impl platform::Driver for CPUFreqDTDriver {
+    type IdInfo = ();
+    const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
+
+    fn probe(
+        pdev: &platform::Device<Core>,
+        _id_info: Option<&Self::IdInfo>,
+    ) -> Result<Pin<KBox<Self>>> {
+        cpufreq::Registration::<CPUFreqDTDriver>::new_foreign_owned(pdev.as_ref())?;
+        Ok(KBox::new(Self {}, GFP_KERNEL)?.into())
+    }
+}
+
+module_platform_driver! {
+    type: CPUFreqDTDriver,
+    name: "cpufreq-dt",
+    author: "Viresh Kumar <[e-mail]>",
+    description: "Generic CPUFreq DT driver",
+    license: "GPL v2",
+}

include/linux/cpufreq.h

···
 	struct notifier_block nb_max;
 };
 
+DEFINE_GUARD(cpufreq_policy_write, struct cpufreq_policy *,
+	     down_write(&_T->rwsem), up_write(&_T->rwsem))
+
+DEFINE_GUARD(cpufreq_policy_read, struct cpufreq_policy *,
+	     down_read(&_T->rwsem), up_read(&_T->rwsem))
+
 /*
  * Used for passing new cpufreq policy data to the cpufreq driver's ->verify()
  * callback for sanitization.  That callback is only expected to modify the min
···
 
 u64 get_cpu_idle_time(unsigned int cpu, u64 *wall, int io_busy);
 
-struct cpufreq_policy *cpufreq_cpu_acquire(unsigned int cpu);
-void cpufreq_cpu_release(struct cpufreq_policy *policy);
 int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu);
 void refresh_frequency_limits(struct cpufreq_policy *policy);
 void cpufreq_update_policy(unsigned int cpu);
···
 	unsigned int	(*get)(unsigned int cpu);
 
 	/* Called to update policy limits on firmware notifications. */
-	void		(*update_limits)(unsigned int cpu);
+	void		(*update_limits)(struct cpufreq_policy *policy);
 
 	/* optional */
 	int		(*bios_limit)(int cpu, unsigned int *limit);

rust/bindings/bindings_helper.h

···
 #include <linux/blk-mq.h>
 #include <linux/blk_types.h>
 #include <linux/blkdev.h>
+#include <linux/clk.h>
+#include <linux/cpu.h>
+#include <linux/cpufreq.h>
 #include <linux/cpumask.h>
 #include <linux/cred.h>
 #include <linux/device/faux.h>
···
 #include <linux/phy.h>
 #include <linux/pid_namespace.h>
 #include <linux/platform_device.h>
+#include <linux/pm_opp.h>
 #include <linux/poll.h>
 #include <linux/property.h>
 #include <linux/refcount.h>

rust/helpers/clk.c

···
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/clk.h>
+
+/*
+ * The "inline" implementation of below helpers are only available when
+ * CONFIG_HAVE_CLK or CONFIG_HAVE_CLK_PREPARE aren't set.
+ */
+#ifndef CONFIG_HAVE_CLK
+struct clk *rust_helper_clk_get(struct device *dev, const char *id)
+{
+	return clk_get(dev, id);
+}
+
+void rust_helper_clk_put(struct clk *clk)
+{
+	clk_put(clk);
+}
+
+int rust_helper_clk_enable(struct clk *clk)
+{
+	return clk_enable(clk);
+}
+
+void rust_helper_clk_disable(struct clk *clk)
+{
+	clk_disable(clk);
+}
+
+unsigned long rust_helper_clk_get_rate(struct clk *clk)
+{
+	return clk_get_rate(clk);
+}
+
+int rust_helper_clk_set_rate(struct clk *clk, unsigned long rate)
+{
+	return clk_set_rate(clk, rate);
+}
+#endif
+
+#ifndef CONFIG_HAVE_CLK_PREPARE
+int rust_helper_clk_prepare(struct clk *clk)
+{
+	return clk_prepare(clk);
+}
+
+void rust_helper_clk_unprepare(struct clk *clk)
+{
+	clk_unprepare(clk);
+}
+#endif
+
+struct clk *rust_helper_clk_get_optional(struct device *dev, const char *id)
+{
+	return clk_get_optional(dev, id);
+}
+
+int rust_helper_clk_prepare_enable(struct clk *clk)
+{
+	return clk_prepare_enable(clk);
+}
+
+void rust_helper_clk_disable_unprepare(struct clk *clk)
+{
+	clk_disable_unprepare(clk);
+}

rust/helpers/cpufreq.c

···
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/cpufreq.h>
+
+#ifdef CONFIG_CPU_FREQ
+void rust_helper_cpufreq_register_em_with_opp(struct cpufreq_policy *policy)
+{
+	cpufreq_register_em_with_opp(policy);
+}
+#endif

rust/helpers/cpumask.c

···
 	cpumask_set_cpu(cpu, dstp);
 }
 
+void rust_helper___cpumask_set_cpu(unsigned int cpu, struct cpumask *dstp)
+{
+	__cpumask_set_cpu(cpu, dstp);
+}
+
 void rust_helper_cpumask_clear_cpu(int cpu, struct cpumask *dstp)
 {
 	cpumask_clear_cpu(cpu, dstp);
 }
 
+void rust_helper___cpumask_clear_cpu(int cpu, struct cpumask *dstp)
+{
+	__cpumask_clear_cpu(cpu, dstp);
+}
+
+bool rust_helper_cpumask_test_cpu(int cpu, struct cpumask *srcp)
+{
+	return cpumask_test_cpu(cpu, srcp);
+}
+
 void rust_helper_cpumask_setall(struct cpumask *dstp)
 {
 	cpumask_setall(dstp);
+}
+
+bool rust_helper_cpumask_empty(struct cpumask *srcp)
+{
+	return cpumask_empty(srcp);
+}
+
+bool rust_helper_cpumask_full(struct cpumask *srcp)
+{
+	return cpumask_full(srcp);
 }
 
 unsigned int rust_helper_cpumask_weight(struct cpumask *srcp)

rust/helpers/helpers.c

···
 #include "bug.c"
 #include "build_assert.c"
 #include "build_bug.c"
+#include "clk.c"
+#include "cpufreq.c"
 #include "cpumask.c"
 #include "cred.c"
 #include "device.c"

rust/kernel/clk.rs

···
+// SPDX-License-Identifier: GPL-2.0
+
+//! Clock abstractions.
+//!
+//! C header: [`include/linux/clk.h`](srctree/include/linux/clk.h)
+//!
+//! Reference: <https://docs.kernel.org/driver-api/clk.html>
+
+use crate::ffi::c_ulong;
+
+/// The frequency unit.
+///
+/// Represents a frequency in hertz, wrapping a [`c_ulong`] value.
+///
+/// ## Examples
+///
+/// ```
+/// use kernel::clk::Hertz;
+///
+/// let hz = 1_000_000_000;
+/// let rate = Hertz(hz);
+///
+/// assert_eq!(rate.as_hz(), hz);
+/// assert_eq!(rate, Hertz(hz));
+/// assert_eq!(rate, Hertz::from_khz(hz / 1_000));
+/// assert_eq!(rate, Hertz::from_mhz(hz / 1_000_000));
+/// assert_eq!(rate, Hertz::from_ghz(hz / 1_000_000_000));
+/// ```
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub struct Hertz(pub c_ulong);
+
+impl Hertz {
+    /// Create a new instance from kilohertz (kHz)
+    pub fn from_khz(khz: c_ulong) -> Self {
+        Self(khz * 1_000)
+    }
+
+    /// Create a new instance from megahertz (MHz)
+    pub fn from_mhz(mhz: c_ulong) -> Self {
+        Self(mhz * 1_000_000)
+    }
+
+    /// Create a new instance from gigahertz (GHz)
+    pub fn from_ghz(ghz: c_ulong) -> Self {
+        Self(ghz * 1_000_000_000)
+    }
+
+    /// Get the frequency in hertz
+    pub fn as_hz(&self) -> c_ulong {
+        self.0
+    }
+
+    /// Get the frequency in kilohertz
+    pub fn as_khz(&self) -> c_ulong {
+        self.0 / 1_000
+    }
+
+    /// Get the frequency in megahertz
+    pub fn as_mhz(&self) -> c_ulong {
+        self.0 / 1_000_000
+    }
+
+    /// Get the frequency in gigahertz
+    pub fn as_ghz(&self) -> c_ulong {
+        self.0 / 1_000_000_000
+    }
+}
+
+impl From<Hertz> for c_ulong {
+    fn from(freq: Hertz) -> Self {
+        freq.0
+    }
+}
+
+#[cfg(CONFIG_COMMON_CLK)]
+mod common_clk {
+    use super::Hertz;
+    use crate::{
+        device::Device,
+        error::{from_err_ptr, to_result, Result},
+        prelude::*,
+    };
+
+    use core::{ops::Deref, ptr};
+
+    /// A reference-counted clock.
+    ///
+    /// Rust abstraction for the C [`struct clk`].
+    ///
+    /// # Invariants
+    ///
+    /// A [`Clk`] instance holds either a pointer to a valid [`struct clk`] created by the C
+    /// portion of the kernel or a NULL pointer.
+    ///
+    /// Instances of this type are reference-counted. Calling [`Clk::get`] ensures that the
+    /// allocation remains valid for the lifetime of the [`Clk`].
+    ///
+    /// ## Examples
+    ///
+    /// The following example demonstrates how to obtain and configure a clock for a device.
+    ///
+    /// ```
+    /// use kernel::c_str;
+    /// use kernel::clk::{Clk, Hertz};
+    /// use kernel::device::Device;
+    /// use kernel::error::Result;
+    ///
+    /// fn configure_clk(dev: &Device) -> Result {
+    ///     let clk = Clk::get(dev, Some(c_str!("apb_clk")))?;
+    ///
+    ///     clk.prepare_enable()?;
+    ///
+    ///     let expected_rate = Hertz::from_ghz(1);
+    ///
+    ///     if clk.rate() != expected_rate {
+    ///         clk.set_rate(expected_rate)?;
+    ///     }
+    ///
+    ///     clk.disable_unprepare();
+    ///     Ok(())
+    /// }
+    /// ```
+    ///
+    /// [`struct clk`]: https://docs.kernel.org/driver-api/clk.html
+    #[repr(transparent)]
+    pub struct Clk(*mut bindings::clk);
+
+    impl Clk {
+        /// Gets [`Clk`] corresponding to a [`Device`] and a connection id.
+        ///
+        /// Equivalent to the kernel's [`clk_get`] API.
+        ///
+        /// [`clk_get`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_get
+        pub fn get(dev: &Device, name: Option<&CStr>) -> Result<Self> {
+            let con_id = if let Some(name) = name {
+                name.as_ptr()
+            } else {
+                ptr::null()
+            };
+
+            // SAFETY: It is safe to call [`clk_get`] for a valid device pointer.
+            //
+            // INVARIANT: The reference-count is decremented when [`Clk`] goes out of scope.
+            Ok(Self(from_err_ptr(unsafe {
+                bindings::clk_get(dev.as_raw(), con_id)
+            })?))
+        }
+
+        /// Obtain the raw [`struct clk`] pointer.
+        #[inline]
+        pub fn as_raw(&self) -> *mut bindings::clk {
+            self.0
+        }
+
+        /// Enable the clock.
+        ///
+        /// Equivalent to the kernel's [`clk_enable`] API.
+        ///
+        /// [`clk_enable`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_enable
+        #[inline]
+        pub fn enable(&self) -> Result {
+            // SAFETY: By the type invariants, self.as_raw() is a valid argument for
+            // [`clk_enable`].
+            to_result(unsafe { bindings::clk_enable(self.as_raw()) })
+        }
+
+        /// Disable the clock.
+        ///
+        /// Equivalent to the kernel's [`clk_disable`] API.
+        ///
+        /// [`clk_disable`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_disable
+        #[inline]
+        pub fn disable(&self) {
+            // SAFETY: By the type invariants, self.as_raw() is a valid argument for
+            // [`clk_disable`].
+            unsafe { bindings::clk_disable(self.as_raw()) };
+        }
+
+        /// Prepare the clock.
+        ///
+        /// Equivalent to the kernel's [`clk_prepare`] API.
+        ///
+        /// [`clk_prepare`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_prepare
+        #[inline]
+        pub fn prepare(&self) -> Result {
+            // SAFETY: By the type invariants, self.as_raw() is a valid argument for
+            // [`clk_prepare`].
+            to_result(unsafe { bindings::clk_prepare(self.as_raw()) })
+        }
+
+        /// Unprepare the clock.
+        ///
+        /// Equivalent to the kernel's [`clk_unprepare`] API.
+        ///
+        /// [`clk_unprepare`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_unprepare
+        #[inline]
+        pub fn unprepare(&self) {
+            // SAFETY: By the type invariants, self.as_raw() is a valid argument for
+            // [`clk_unprepare`].
+            unsafe { bindings::clk_unprepare(self.as_raw()) };
+        }
+
+        /// Prepare and enable the clock.
+        ///
+        /// Equivalent to calling [`Clk::prepare`] followed by [`Clk::enable`].
+        #[inline]
+        pub fn prepare_enable(&self) -> Result {
+            // SAFETY: By the type invariants, self.as_raw() is a valid argument for
+            // [`clk_prepare_enable`].
+            to_result(unsafe { bindings::clk_prepare_enable(self.as_raw()) })
+        }
+
+        /// Disable and unprepare the clock.
+        ///
+        /// Equivalent to calling [`Clk::disable`] followed by [`Clk::unprepare`].
+        #[inline]
+        pub fn disable_unprepare(&self) {
+            // SAFETY: By the type invariants, self.as_raw() is a valid argument for
+            // [`clk_disable_unprepare`].
+            unsafe { bindings::clk_disable_unprepare(self.as_raw()) };
+        }
+
+        /// Get clock's rate.
+        ///
+        /// Equivalent to the kernel's [`clk_get_rate`] API.
+        ///
+        /// [`clk_get_rate`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_get_rate
+        #[inline]
+        pub fn rate(&self) -> Hertz {
+            // SAFETY: By the type invariants, self.as_raw() is a valid argument for
+            // [`clk_get_rate`].
+            Hertz(unsafe { bindings::clk_get_rate(self.as_raw()) })
+        }
+
+        /// Set clock's rate.
+        ///
+        /// Equivalent to the kernel's [`clk_set_rate`] API.
+        ///
+        /// [`clk_set_rate`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_set_rate
+        #[inline]
+        pub fn set_rate(&self, rate: Hertz) -> Result {
+            // SAFETY: By the type invariants, self.as_raw() is a valid argument for
+            // [`clk_set_rate`].
+            to_result(unsafe { bindings::clk_set_rate(self.as_raw(), rate.as_hz()) })
+        }
+    }
+
+    impl Drop for Clk {
+        fn drop(&mut self) {
+            // SAFETY: By the type invariants, self.as_raw() is a valid argument for [`clk_put`].
+            unsafe { bindings::clk_put(self.as_raw()) };
+        }
+    }
+
+    /// A reference-counted optional clock.
+    ///
+    /// A lightweight wrapper around an optional [`Clk`]. An [`OptionalClk`] represents a [`Clk`]
+    /// that a driver can function without but may improve performance or enable additional
+    /// features when available.
+    ///
+    /// # Invariants
+    ///
+    /// An [`OptionalClk`] instance encapsulates a [`Clk`] with either a valid [`struct clk`] or
+    /// `NULL` pointer.
+    ///
+    /// Instances of this type are reference-counted. Calling [`OptionalClk::get`] ensures that the
+    /// allocation remains valid for the lifetime of the [`OptionalClk`].
+    ///
+    /// ## Examples
+    ///
+    /// The following example demonstrates how to obtain and configure an optional clock for a
+    /// device. The code functions correctly whether or not the clock is available.
+    ///
+    /// ```
+    /// use kernel::c_str;
+    /// use kernel::clk::{OptionalClk, Hertz};
+    /// use kernel::device::Device;
+    /// use kernel::error::Result;
+    ///
+    /// fn configure_clk(dev: &Device) -> Result {
+    ///     let clk = OptionalClk::get(dev, Some(c_str!("apb_clk")))?;
+    ///
+    ///     clk.prepare_enable()?;
+    ///
+    ///     let expected_rate = Hertz::from_ghz(1);
+    ///
+    ///     if clk.rate() != expected_rate {
+    ///         clk.set_rate(expected_rate)?;
+    ///     }
+    ///
+    ///     clk.disable_unprepare();
+    ///     Ok(())
+    /// }
+    /// ```
+    ///
+    /// [`struct clk`]: https://docs.kernel.org/driver-api/clk.html
+    pub struct OptionalClk(Clk);
+
+    impl OptionalClk {
+        /// Gets [`OptionalClk`] corresponding to a [`Device`] and a connection id.
+        ///
+        /// Equivalent to the kernel's [`clk_get_optional`] API.
+        ///
+        /// [`clk_get_optional`]:
+        /// https://docs.kernel.org/core-api/kernel-api.html#c.clk_get_optional
+        pub fn get(dev: &Device, name: Option<&CStr>) -> Result<Self> {
+            let con_id = if let Some(name) = name {
+                name.as_ptr()
+            } else {
+                ptr::null()
+            };
+
+            // SAFETY: It is safe to call [`clk_get_optional`] for a valid device pointer.
+            //
+            // INVARIANT: The reference-count is decremented when [`OptionalClk`] goes out of
+            // scope.
+            Ok(Self(Clk(from_err_ptr(unsafe {
+                bindings::clk_get_optional(dev.as_raw(), con_id)
+            })?)))
+        }
+    }
+
+    // Make [`OptionalClk`] behave like [`Clk`].
+    impl Deref for OptionalClk {
+        type Target = Clk;
+
+        fn deref(&self) -> &Clk {
+            &self.0
+        }
+    }
+}
+
+#[cfg(CONFIG_COMMON_CLK)]
+pub use common_clk::*;

rust/kernel/cpu.rs

···
+// SPDX-License-Identifier: GPL-2.0
+
+//! Generic CPU definitions.
+//!
+//! C header: [`include/linux/cpu.h`](srctree/include/linux/cpu.h)
+
+use crate::{bindings, device::Device, error::Result, prelude::ENODEV};
+
+/// Creates a new instance of CPU's device.
+///
+/// # Safety
+///
+/// Reference counting is not implemented for the CPU device in the C code. When a CPU is
+/// hot-unplugged, the corresponding CPU device is unregistered, but its associated memory
+/// is not freed.
+///
+/// Callers must ensure that the CPU device is not used after it has been unregistered.
+/// This can be achieved, for example, by registering a CPU hotplug notifier and removing
+/// any references to the CPU device within the notifier's callback.
+pub unsafe fn from_cpu(cpu: u32) -> Result<&'static Device> {
+    // SAFETY: It is safe to call `get_cpu_device()` for any CPU.
+    let ptr = unsafe { bindings::get_cpu_device(cpu) };
+    if ptr.is_null() {
+        return Err(ENODEV);
+    }
+
+    // SAFETY: The pointer returned by `get_cpu_device()`, if not `NULL`, is a valid pointer to
+    // a `struct device` and is never freed by the C code.
+    Ok(unsafe { Device::as_ref(ptr) })
+}

rust/kernel/cpufreq.rs

···
+// SPDX-License-Identifier: GPL-2.0
+
+//! CPU frequency scaling.
+//!
+//! This module provides rust abstractions for interacting with the cpufreq subsystem.
+//!
+//! C header: [`include/linux/cpufreq.h`](srctree/include/linux/cpufreq.h)
+//!
+//! Reference: <https://docs.kernel.org/admin-guide/pm/cpufreq.html>
+
+use crate::{
+    clk::Hertz,
+    cpumask,
+    device::{Bound, Device},
+    devres::Devres,
+    error::{code::*, from_err_ptr, from_result, to_result, Result, VTABLE_DEFAULT_ERROR},
+    ffi::{c_char, c_ulong},
+    prelude::*,
+    types::ForeignOwnable,
+    types::Opaque,
+};
+
+#[cfg(CONFIG_COMMON_CLK)]
+use crate::clk::Clk;
+
+use core::{
+    cell::UnsafeCell,
+    marker::PhantomData,
+    mem::MaybeUninit,
+    ops::{Deref, DerefMut},
+    pin::Pin,
+    ptr,
+};
+
+use macros::vtable;
+
+/// Maximum length of CPU frequency driver's name.
+const CPUFREQ_NAME_LEN: usize = bindings::CPUFREQ_NAME_LEN as usize;
+
+/// Default transition latency value in nanoseconds.
+pub const ETERNAL_LATENCY_NS: u32 = bindings::CPUFREQ_ETERNAL as u32;
+
+/// CPU frequency driver flags.
+pub mod flags {
+    /// Driver needs to update internal limits even if frequency remains unchanged.
+    pub const NEED_UPDATE_LIMITS: u16 = 1 << 0;
+
+    /// Platform where constants like `loops_per_jiffy` are unaffected by frequency changes.
+    pub const CONST_LOOPS: u16 = 1 << 1;
+
+    /// Register driver as a thermal cooling device automatically.
+    pub const IS_COOLING_DEV: u16 = 1 << 2;
+
+    /// Supports multiple clock domains with per-policy governors in `cpu/cpuN/cpufreq/`.
+    pub const HAVE_GOVERNOR_PER_POLICY: u16 = 1 << 3;
+
+    /// Allows post-change notifications outside of the `target()` routine.
+    pub const ASYNC_NOTIFICATION: u16 = 1 << 4;
+
+    /// Ensure CPU starts at a valid frequency from the driver's freq-table.
+    pub const NEED_INITIAL_FREQ_CHECK: u16 = 1 << 5;
+
+    /// Disallow governors with `dynamic_switching` capability.
+    pub const NO_AUTO_DYNAMIC_SWITCHING: u16 = 1 << 6;
+}
+
+/// Relations from the C code.
+const CPUFREQ_RELATION_L: u32 = 0;
+const CPUFREQ_RELATION_H: u32 = 1;
+const CPUFREQ_RELATION_C: u32 = 2;
+
+/// Can be used with any of the above values.
+const CPUFREQ_RELATION_E: u32 = 1 << 2;
+
+/// CPU frequency selection relations.
+///
+/// CPU frequency selection relations, each optionally marked as "efficient".
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub enum Relation {
+    /// Select the lowest frequency at or above target.
+    Low(bool),
+    /// Select the highest frequency below or at target.
+    High(bool),
+    /// Select the closest frequency to the target.
+    Close(bool),
+}
+
+impl Relation {
+    // Construct from a C-compatible `u32` value.
+    fn new(val: u32) -> Result<Self> {
+        let efficient = val & CPUFREQ_RELATION_E != 0;
+
+        Ok(match val & !CPUFREQ_RELATION_E {
+            CPUFREQ_RELATION_L => Self::Low(efficient),
+            CPUFREQ_RELATION_H => Self::High(efficient),
+            CPUFREQ_RELATION_C => Self::Close(efficient),
+            _ => return Err(EINVAL),
+        })
+    }
+}
+
+impl From<Relation> for u32 {
+    // Convert to a C-compatible `u32` value.
+    fn from(rel: Relation) -> Self {
+        let (mut val, efficient) = match rel {
+            Relation::Low(e) => (CPUFREQ_RELATION_L, e),
+            Relation::High(e) => (CPUFREQ_RELATION_H, e),
+            Relation::Close(e) => (CPUFREQ_RELATION_C, e),
+        };
+
+        if efficient {
+            val |= CPUFREQ_RELATION_E;
+        }
+
+        val
+    }
+}
+
+/// Policy data.
+///
+/// Rust abstraction for the C `struct cpufreq_policy_data`.
+///
+/// # Invariants
+///
+/// A [`PolicyData`] instance always corresponds to a valid C `struct cpufreq_policy_data`.
+///
+/// The callers must ensure that the `struct cpufreq_policy_data` is valid for access and remains
+/// valid for the lifetime of the returned reference.
+#[repr(transparent)]
+pub struct PolicyData(Opaque<bindings::cpufreq_policy_data>);
+
+impl PolicyData {
+    /// Creates a mutable reference to an existing `struct cpufreq_policy_data` pointer.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that `ptr` is valid for writing and remains valid for the lifetime
+    /// of the returned reference.
+    #[inline]
+    pub unsafe fn from_raw_mut<'a>(ptr: *mut bindings::cpufreq_policy_data) -> &'a mut Self {
+        // SAFETY: Guaranteed by the safety requirements of the function.
+        //
+        // INVARIANT: The caller ensures that `ptr` is valid for writing and remains valid for the
+        // lifetime of the returned reference.
+        unsafe { &mut *ptr.cast() }
+    }
+
+    /// Returns a raw pointer to the underlying C `cpufreq_policy_data`.
+    #[inline]
+    pub fn as_raw(&self) -> *mut bindings::cpufreq_policy_data {
+        let this: *const Self = self;
+        this.cast_mut().cast()
+    }
+
+    /// Wrapper for `cpufreq_generic_frequency_table_verify`.
+    #[inline]
+    pub fn generic_verify(&self) -> Result {
+        // SAFETY: By the type invariant, the pointer stored in `self` is valid.
+        to_result(unsafe { bindings::cpufreq_generic_frequency_table_verify(self.as_raw()) })
+    }
+}
+
+/// The frequency table index.
+///
+/// Represents index with a frequency table.
+///
+/// # Invariants
+///
+/// The index must correspond to a valid entry in the [`Table`] it is used for.
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub struct TableIndex(usize);
+
+impl TableIndex {
+    /// Creates an instance of [`TableIndex`].
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that `index` correspond to a valid entry in the [`Table`] it is used
+    /// for.
+    pub unsafe fn new(index: usize) -> Self {
+        // INVARIANT: The caller ensures that `index` correspond to a valid entry in the [`Table`].
+        Self(index)
+    }
+}
+
+impl From<TableIndex> for usize {
+    #[inline]
+    fn from(index: TableIndex) -> Self {
+        index.0
+    }
+}
+
+/// CPU frequency table.
+///
+/// Rust abstraction for the C `struct cpufreq_frequency_table`.
+///
+/// # Invariants
+///
+/// A [`Table`] instance always corresponds to a valid C `struct cpufreq_frequency_table`.
+///
+/// The callers must ensure that the `struct cpufreq_frequency_table` is valid for access and
+/// remains valid for the lifetime of the returned reference.
+///
+/// ## Examples
+///
+/// The following example demonstrates how to read a frequency value from [`Table`].
+///
+/// ```
+/// use kernel::cpufreq::{Policy, TableIndex};
+///
+/// fn show_freq(policy: &Policy) -> Result {
+///     let table = policy.freq_table()?;
+///
+///     // SAFETY: Index is a valid entry in the table.
+///     let index = unsafe { TableIndex::new(0) };
+///
+///     pr_info!("The frequency at index 0 is: {:?}\n", table.freq(index)?);
+///     pr_info!("The flags at index 0 is: {}\n", table.flags(index));
+///     pr_info!("The data at index 0 is: {}\n", table.data(index));
+///     Ok(())
+/// }
+/// ```
+#[repr(transparent)]
+pub struct Table(Opaque<bindings::cpufreq_frequency_table>);
+
+impl Table {
+    /// Creates a reference to an existing C `struct cpufreq_frequency_table` pointer.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that `ptr` is valid for reading and remains valid for the lifetime
+    /// of the returned reference.
+    #[inline]
+    pub unsafe fn from_raw<'a>(ptr: *const bindings::cpufreq_frequency_table) -> &'a Self {
+        // SAFETY: Guaranteed by the safety requirements of the function.
+        //
+        // INVARIANT: The caller ensures that `ptr` is valid for reading and remains valid for the
+        // lifetime of the returned reference.
+        unsafe { &*ptr.cast() }
+    }
+
+    /// Returns the raw mutable pointer to the C `struct cpufreq_frequency_table`.
+    #[inline]
+    pub fn as_raw(&self) -> *mut bindings::cpufreq_frequency_table {
+        let this: *const Self = self;
+        this.cast_mut().cast()
+    }
+
+    /// Returns frequency at `index` in the [`Table`].
+    #[inline]
+    pub fn freq(&self, index: TableIndex) -> Result<Hertz> {
+        // SAFETY: By the type invariant, the pointer stored in `self` is valid and `index` is
+        // guaranteed to be valid by its safety requirements.
+        Ok(Hertz::from_khz(unsafe {
+            (*self.as_raw().add(index.into())).frequency.try_into()?
+        }))
+    }
+
+    /// Returns flags at `index` in the [`Table`].
+    #[inline]
+    pub fn flags(&self, index: TableIndex) -> u32 {
+        // SAFETY: By the type invariant, the pointer stored in `self` is valid and `index` is
+        // guaranteed to be valid by its safety requirements.
+        unsafe { (*self.as_raw().add(index.into())).flags }
+    }
+
+    /// Returns data at `index` in the [`Table`].
+    #[inline]
+    pub fn data(&self, index: TableIndex) -> u32 {
+        // SAFETY: By the type invariant, the pointer stored in `self` is valid and `index` is
+        // guaranteed to be valid by its safety requirements.
+        unsafe { (*self.as_raw().add(index.into())).driver_data }
+    }
+}
+
+/// CPU frequency table owned and pinned in memory, created from a [`TableBuilder`].
+pub struct TableBox {
+    entries: Pin<KVec<bindings::cpufreq_frequency_table>>,
+}
+
+impl TableBox {
+    /// Constructs a new [`TableBox`] from a [`KVec`] of entries.
+    ///
+    /// # Errors
+    ///
+    /// Returns `EINVAL` if the entries list is empty.
+    #[inline]
+    fn new(entries: KVec<bindings::cpufreq_frequency_table>) -> Result<Self> {
+        if entries.is_empty() {
+            return Err(EINVAL);
+        }
+
+        Ok(Self {
+            // Pin the entries to memory, since we are passing its pointer to the C code.
+            entries: Pin::new(entries),
+        })
+    }
+
+    /// Returns a raw pointer to the underlying C `cpufreq_frequency_table`.
+    #[inline]
+    fn as_raw(&self) -> *const bindings::cpufreq_frequency_table {
+        // The pointer is valid until the table gets dropped.
+        self.entries.as_ptr()
+    }
+}
+
+impl Deref for TableBox {
+    type Target = Table;
+
+    fn deref(&self) -> &Self::Target {
+        // SAFETY: The caller owns TableBox, it is safe to deref.
+        unsafe { Self::Target::from_raw(self.as_raw()) }
+    }
+}
+
+/// CPU frequency table builder.
+///
+/// This is used by the CPU frequency drivers to build a frequency table dynamically.
+///
+/// ## Examples
+///
+/// The following example demonstrates how to create a CPU frequency table.
+///
+/// ```
+/// use kernel::cpufreq::{TableBuilder, TableIndex};
+/// use kernel::clk::Hertz;
+///
+/// let mut builder = TableBuilder::new();
+///
+/// // Adds few entries to the table.
+/// builder.add(Hertz::from_mhz(700), 0, 1).unwrap();
+/// builder.add(Hertz::from_mhz(800), 2, 3).unwrap();
+/// builder.add(Hertz::from_mhz(900), 4, 5).unwrap();
+/// builder.add(Hertz::from_ghz(1), 6, 7).unwrap();
+///
+/// let table = builder.to_table().unwrap();
+///
+/// // SAFETY: Index values correspond to valid entries in the table.
+/// let (index0, index2) = unsafe { (TableIndex::new(0), TableIndex::new(2)) };
+///
+/// assert_eq!(table.freq(index0), Ok(Hertz::from_mhz(700)));
+/// assert_eq!(table.flags(index0), 0);
+/// assert_eq!(table.data(index0), 1);
+///
+/// assert_eq!(table.freq(index2), Ok(Hertz::from_mhz(900)));
+/// assert_eq!(table.flags(index2), 4);
+/// assert_eq!(table.data(index2), 5);
+/// ```
+#[derive(Default)]
+#[repr(transparent)]
+pub struct TableBuilder {
+    entries: KVec<bindings::cpufreq_frequency_table>,
+}
+
+impl TableBuilder {
+    /// Creates a new instance of [`TableBuilder`].
+    #[inline]
+    pub fn new() -> Self {
+        Self {
+            entries: KVec::new(),
+        }
+    }
+
+    /// Adds a new entry to the table.
+    pub fn add(&mut self, freq: Hertz, flags: u32, driver_data: u32) -> Result {
+        // Adds the new entry at the end of the vector.
+        Ok(self.entries.push(
+            bindings::cpufreq_frequency_table {
+                flags,
+                driver_data,
+                frequency: freq.as_khz() as u32,
+            },
+            GFP_KERNEL,
+        )?)
+    }
+
+    /// Consumes the [`TableBuilder`] and returns [`TableBox`].
+    pub fn to_table(mut self) -> Result<TableBox> {
+        // Add last entry to the table.
+        self.add(Hertz(c_ulong::MAX), 0, 0)?;
+
+        TableBox::new(self.entries)
+    }
+}
+
+/// CPU frequency policy.
+///
+/// Rust abstraction for the C `struct cpufreq_policy`.
+///
+/// # Invariants
+///
+/// A [`Policy`] instance always corresponds to a valid C `struct cpufreq_policy`.
+///
+/// The callers must ensure that the `struct cpufreq_policy` is valid for access and remains valid
+/// for the lifetime of the returned reference.
+///
+/// ## Examples
+///
+/// The following example demonstrates how to create a CPU frequency table.
+///
+/// ```
+/// use kernel::cpufreq::{ETERNAL_LATENCY_NS, Policy};
+///
+/// fn update_policy(policy: &mut Policy) {
+///     policy
+///         .set_dvfs_possible_from_any_cpu(true)
+///         .set_fast_switch_possible(true)
+///         .set_transition_latency_ns(ETERNAL_LATENCY_NS);
+///
+///     pr_info!("The policy details are: {:?}\n", (policy.cpu(), policy.cur()));
+/// }
+/// ```
+#[repr(transparent)]
+pub struct Policy(Opaque<bindings::cpufreq_policy>);
+
+impl Policy {
+    /// Creates a reference to an existing `struct cpufreq_policy` pointer.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that `ptr` is valid for reading and remains valid for the lifetime
+    /// of the returned reference.
+    #[inline]
+    pub unsafe fn from_raw<'a>(ptr: *const bindings::cpufreq_policy) -> &'a Self {
+        // SAFETY: Guaranteed by the safety requirements of the function.
+        //
+        // INVARIANT: The caller ensures that `ptr` is valid for reading and remains valid for the
+        // lifetime of the returned reference.
+        unsafe { &*ptr.cast() }
+    }
+
+    /// Creates a mutable reference to an existing `struct cpufreq_policy` pointer.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that `ptr` is valid for writing and remains valid for the lifetime
+    /// of the returned reference.
+    #[inline]
+    pub unsafe fn from_raw_mut<'a>(ptr: *mut bindings::cpufreq_policy) -> &'a mut Self {
+        // SAFETY: Guaranteed by the safety requirements of the function.
+        //
+        // INVARIANT: The caller ensures that `ptr` is valid for writing and remains valid for the
+        // lifetime of the returned reference.
+        unsafe { &mut *ptr.cast() }
+    }
+
+    /// Returns a raw mutable pointer to the C `struct cpufreq_policy`.
+    #[inline]
+    fn as_raw(&self) -> *mut bindings::cpufreq_policy {
+        let this: *const Self = self;
+        this.cast_mut().cast()
+    }
+
+    #[inline]
+    fn as_ref(&self) -> &bindings::cpufreq_policy {
+        // SAFETY: By the type invariant, the pointer stored in `self` is valid.
+        unsafe { &*self.as_raw() }
+    }
+
+    #[inline]
+    fn as_mut_ref(&mut self) -> &mut bindings::cpufreq_policy {
+        // SAFETY: By the type invariant, the pointer stored in `self` is valid.
+        unsafe { &mut *self.as_raw() }
+    }
+
+    /// Returns the primary CPU for the [`Policy`].
+    #[inline]
+    pub fn cpu(&self) -> u32 {
+        self.as_ref().cpu
+    }
+
+    /// Returns the minimum frequency for the [`Policy`].
+    #[inline]
+    pub fn min(&self) -> Hertz {
+        Hertz::from_khz(self.as_ref().min as usize)
+    }
+
+    /// Set the minimum frequency for the [`Policy`].
+    #[inline]
+    pub fn set_min(&mut self, min: Hertz) -> &mut Self {
+        self.as_mut_ref().min = min.as_khz() as u32;
+        self
+    }
+
+    /// Returns the maximum frequency for the [`Policy`].
+    #[inline]
+    pub fn max(&self) -> Hertz {
+        Hertz::from_khz(self.as_ref().max as usize)
+    }
+
+    /// Set the maximum frequency for the [`Policy`].
+    #[inline]
+    pub fn set_max(&mut self, max: Hertz) -> &mut Self {
+        self.as_mut_ref().max = max.as_khz() as u32;
+        self
+    }
+
+    /// Returns the current frequency for the [`Policy`].
+    #[inline]
+    pub fn cur(&self) -> Hertz {
+        Hertz::from_khz(self.as_ref().cur as usize)
+    }
+
+    /// Returns the suspend frequency for the [`Policy`].
+    #[inline]
+    pub fn suspend_freq(&self) -> Hertz {
+        Hertz::from_khz(self.as_ref().suspend_freq as usize)
+    }
+
+    /// Sets the suspend frequency for the [`Policy`].
+    #[inline]
+    pub fn set_suspend_freq(&mut self, freq: Hertz) -> &mut Self {
+        self.as_mut_ref().suspend_freq = freq.as_khz() as u32;
+        self
+    }
+
+    /// Provides a wrapper to the generic suspend routine.
+    #[inline]
+    pub fn generic_suspend(&mut self) -> Result {
+        // SAFETY: By the type invariant, the pointer stored in `self` is valid.
+        to_result(unsafe { bindings::cpufreq_generic_suspend(self.as_mut_ref()) })
+    }
+
+    /// Provides a wrapper to the generic get routine.
+    #[inline]
+    pub fn generic_get(&self) -> Result<u32> {
+        // SAFETY: By the type invariant, the pointer stored in `self` is valid.
+        Ok(unsafe { bindings::cpufreq_generic_get(self.cpu()) })
+    }
+
+    /// Provides a wrapper to the register with energy model using the OPP core.
+    #[cfg(CONFIG_PM_OPP)]
+    #[inline]
+    pub fn register_em_opp(&mut self) {
+        // SAFETY: By the type invariant, the pointer stored in `self` is valid.
+        unsafe { bindings::cpufreq_register_em_with_opp(self.as_mut_ref()) };
+    }
+
+    /// Gets [`cpumask::Cpumask`] for a cpufreq [`Policy`].
+    #[inline]
+    pub fn cpus(&mut self) -> &mut cpumask::Cpumask {
+        // SAFETY: The pointer to `cpus` is valid for writing and remains valid for the lifetime of
+        // the returned reference.
+        unsafe { cpumask::CpumaskVar::as_mut_ref(&mut self.as_mut_ref().cpus) }
+    }
+
+    /// Sets clock for the [`Policy`].
+    ///
+    /// # Safety
+    ///
+    /// The caller must guarantee that the returned [`Clk`] is not dropped while it is getting used
+    /// by the C code.
+    #[cfg(CONFIG_COMMON_CLK)]
+    pub unsafe fn set_clk(&mut self, dev: &Device, name: Option<&CStr>) -> Result<Clk> {
+        let clk = Clk::get(dev, name)?;
+        self.as_mut_ref().clk = clk.as_raw();
+        Ok(clk)
+    }
+
+    /// Allows / disallows frequency switching code to run on any CPU.
+    #[inline]
+    pub fn set_dvfs_possible_from_any_cpu(&mut self, val: bool) -> &mut Self {
+        self.as_mut_ref().dvfs_possible_from_any_cpu = val;
+        self
+    }
+
+    /// Returns if fast switching of frequencies is possible or not.
+    #[inline]
+    pub fn fast_switch_possible(&self) -> bool {
+        self.as_ref().fast_switch_possible
+    }
+
+    /// Enables / disables fast frequency switching.
+    #[inline]
+    pub fn set_fast_switch_possible(&mut self, val: bool) -> &mut Self {
+        self.as_mut_ref().fast_switch_possible = val;
+        self
+    }
+
+    /// Sets transition latency (in nanoseconds) for the [`Policy`].
+    #[inline]
+    pub fn set_transition_latency_ns(&mut self, latency_ns: u32) -> &mut Self {
+        self.as_mut_ref().cpuinfo.transition_latency = latency_ns;
+        self
+    }
+
+    /// Sets cpuinfo `min_freq`.
+    #[inline]
+    pub fn set_cpuinfo_min_freq(&mut self, min_freq: Hertz) -> &mut Self {
+        self.as_mut_ref().cpuinfo.min_freq = min_freq.as_khz() as u32;
+        self
+    }
+
+    /// Sets cpuinfo `max_freq`.
+    #[inline]
+    pub fn set_cpuinfo_max_freq(&mut self, max_freq: Hertz) -> &mut Self {
+        self.as_mut_ref().cpuinfo.max_freq = max_freq.as_khz() as u32;
+        self
+    }
+
+    /// Set `transition_delay_us`, i.e. the minimum time between successive frequency change
+    /// requests.
+    #[inline]
+    pub fn set_transition_delay_us(&mut self, transition_delay_us: u32) -> &mut Self {
+        self.as_mut_ref().transition_delay_us = transition_delay_us;
+        self
+    }
+
+    /// Returns reference to the CPU frequency [`Table`] for the [`Policy`].
+    pub fn freq_table(&self) -> Result<&Table> {
+        if self.as_ref().freq_table.is_null() {
+            return Err(EINVAL);
+        }
+
+        // SAFETY: The `freq_table` is guaranteed to be valid for reading and remains valid for the
+        // lifetime of the returned reference.
+        Ok(unsafe { Table::from_raw(self.as_ref().freq_table) })
+    }
+
+    /// Sets the CPU frequency [`Table`] for the [`Policy`].
+    ///
+    /// # Safety
+    ///
+    /// The caller must guarantee that the [`Table`] is not dropped while it is getting used by the
+    /// C code.
+    #[inline]
+    pub unsafe fn set_freq_table(&mut self, table: &Table) -> &mut Self {
+        self.as_mut_ref().freq_table = table.as_raw();
+        self
+    }
+
+    /// Returns the [`Policy`]'s private data.
+    pub fn data<T: ForeignOwnable>(&mut self) -> Option<<T>::Borrowed<'_>> {
+        if self.as_ref().driver_data.is_null() {
+            None
+        } else {
+            // SAFETY: The data is earlier set from [`set_data`].
+            Some(unsafe { T::borrow(self.as_ref().driver_data) })
+        }
+    }
+
+    /// Sets the private data of the [`Policy`] using a foreign-ownable wrapper.
+    ///
+    /// # Errors
+    ///
+    /// Returns `EBUSY` if private data is already set.
+    fn set_data<T: ForeignOwnable>(&mut self, data: T) -> Result {
+        if self.as_ref().driver_data.is_null() {
+            // Transfer the ownership of the data to the foreign interface.
+            self.as_mut_ref().driver_data = <T as ForeignOwnable>::into_foreign(data) as _;
+            Ok(())
+        } else {
+            Err(EBUSY)
+        }
+    }
+
+    /// Clears and returns ownership of the private data.
+    fn clear_data<T: ForeignOwnable>(&mut self) -> Option<T> {
+        if self.as_ref().driver_data.is_null() {
+            None
+        } else {
+            let data = Some(
+                // SAFETY: The data is earlier set by us from [`set_data`]. It is safe to take
+                // back the ownership of the data from the foreign interface.
+                unsafe { <T as ForeignOwnable>::from_foreign(self.as_ref().driver_data) },
+            );
+            self.as_mut_ref().driver_data = ptr::null_mut();
+            data
+        }
+    }
+}
+
+/// CPU frequency policy created from a CPU number.
+///
+/// This struct represents the CPU frequency policy obtained for a specific CPU, providing safe
+/// access to the underlying `cpufreq_policy` and ensuring proper cleanup when the `PolicyCpu` is
+/// dropped.
+struct PolicyCpu<'a>(&'a mut Policy);
+
+impl<'a> PolicyCpu<'a> {
+    fn from_cpu(cpu: u32) -> Result<Self> {
+        // SAFETY: It is safe to call `cpufreq_cpu_get` for any valid CPU.
+        let ptr = from_err_ptr(unsafe { bindings::cpufreq_cpu_get(cpu) })?;
+
+        Ok(Self(
+            // SAFETY: The `ptr` is guaranteed to be valid and remains valid for the lifetime of
+            // the returned reference.
+            unsafe { Policy::from_raw_mut(ptr) },
+        ))
+    }
+}
+
+impl<'a> Deref for PolicyCpu<'a> {
+    type Target = Policy;
+
+    fn deref(&self) -> &Self::Target {
+        self.0
+    }
+}
+
+impl<'a> DerefMut for PolicyCpu<'a> {
+    fn deref_mut(&mut self) -> &mut Policy {
+        self.0
+    }
+}
+
+impl<'a> Drop for PolicyCpu<'a> {
+    fn drop(&mut self) {
+        // SAFETY: The underlying pointer is guaranteed to be valid for the lifetime of `self`.
+        unsafe { bindings::cpufreq_cpu_put(self.0.as_raw()) };
+    }
+}
+
+/// CPU frequency driver.
+///
+/// Implement this trait to provide a CPU frequency driver and its callbacks.
+///
+/// Reference: <https://docs.kernel.org/cpu-freq/cpu-drivers.html>
+#[vtable]
+pub trait Driver {
+    /// Driver's name.
+    const NAME: &'static CStr;
+
+    /// Driver's flags.
+    const FLAGS: u16;
+
+    /// Boost support.
+    const BOOST_ENABLED: bool;
+
+    /// Policy specific data.
+    ///
+    /// Require that `PData` implements `ForeignOwnable`. We guarantee to never move the underlying
+    /// wrapped data structure.
+    type PData: ForeignOwnable;
+
+    /// Driver's `init` callback.
+    fn init(policy: &mut Policy) -> Result<Self::PData>;
+
+    /// Driver's `exit` callback.
+    fn exit(_policy: &mut Policy, _data: Option<Self::PData>) -> Result {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `online` callback.
+    fn online(_policy: &mut Policy) -> Result {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `offline` callback.
+    fn offline(_policy: &mut Policy) -> Result {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `suspend` callback.
+    fn suspend(_policy: &mut Policy) -> Result {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `resume` callback.
+    fn resume(_policy: &mut Policy) -> Result {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `ready` callback.
+    fn ready(_policy: &mut Policy) {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `verify` callback.
+    fn verify(data: &mut PolicyData) -> Result;
+
+    /// Driver's `setpolicy` callback.
+    fn setpolicy(_policy: &mut Policy) -> Result {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `target` callback.
+    fn target(_policy: &mut Policy, _target_freq: u32, _relation: Relation) -> Result {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `target_index` callback.
+    fn target_index(_policy: &mut Policy, _index: TableIndex) -> Result {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `fast_switch` callback.
+    fn fast_switch(_policy: &mut Policy, _target_freq: u32) -> u32 {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `adjust_perf` callback.
+    fn adjust_perf(_policy: &mut Policy, _min_perf: usize, _target_perf: usize, _capacity: usize) {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `get_intermediate` callback.
+    fn get_intermediate(_policy: &mut Policy, _index: TableIndex) -> u32 {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `target_intermediate` callback.
+    fn target_intermediate(_policy: &mut Policy, _index: TableIndex) -> Result {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `get` callback.
+    fn get(_policy: &mut Policy) -> Result<u32> {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `update_limits` callback.
+    fn update_limits(_policy: &mut Policy) {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `bios_limit` callback.
+    fn bios_limit(_policy: &mut Policy, _limit: &mut u32) -> Result {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `set_boost` callback.
+    fn set_boost(_policy: &mut Policy, _state: i32) -> Result {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Driver's `register_em` callback.
+    fn register_em(_policy: &mut Policy) {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+}
+
+/// CPU frequency driver Registration.
+///
+/// ## Examples
+///
+/// The following example demonstrates how to register a cpufreq driver.
+///
+/// ```
+/// use kernel::{
+///     cpufreq,
+///     c_str,
+///     device::{Core, Device},
+///     macros::vtable,
+///     of, platform,
+///     sync::Arc,
+/// };
+/// struct SampleDevice;
+///
+/// #[derive(Default)]
+/// struct SampleDriver;
+///
+/// #[vtable]
+/// impl cpufreq::Driver for SampleDriver {
+///     const NAME: &'static CStr = c_str!("cpufreq-sample");
+///     const FLAGS: u16 = cpufreq::flags::NEED_INITIAL_FREQ_CHECK | cpufreq::flags::IS_COOLING_DEV;
+///     const BOOST_ENABLED: bool = true;
+///
+///     type PData = Arc<SampleDevice>;
+///
+///     fn init(policy: &mut cpufreq::Policy) -> Result<Self::PData> {
+///         // Initialize here
+///         Ok(Arc::new(SampleDevice, GFP_KERNEL)?)
+///     }
+///
+///     fn exit(_policy: &mut cpufreq::Policy, _data: Option<Self::PData>) -> Result {
+///         Ok(())
+///     }
+///
+///     fn suspend(policy: &mut cpufreq::Policy) -> Result {
+///         policy.generic_suspend()
+///     }
+///
+///     fn verify(data: &mut cpufreq::PolicyData) -> Result {
+///         data.generic_verify()
+///     }
+///
+///     fn target_index(policy: &mut cpufreq::Policy, index: cpufreq::TableIndex) -> Result {
+///         // Update CPU frequency
+///         Ok(())
+///     }
+///
+///     fn get(policy: &mut cpufreq::Policy) -> Result<u32> {
+///         policy.generic_get()
+///     }
+/// }
+///
+/// impl platform::Driver for SampleDriver {
+///     type IdInfo = ();
+///     const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = None;
+///
+///     fn probe(
+///         pdev: &platform::Device<Core>,
+///         _id_info: Option<&Self::IdInfo>,
+///     ) -> Result<Pin<KBox<Self>>> {
+///         cpufreq::Registration::<SampleDriver>::new_foreign_owned(pdev.as_ref())?;
+///         Ok(KBox::new(Self {}, GFP_KERNEL)?.into())
+///     }
+/// }
+/// ```
+#[repr(transparent)]
+pub struct Registration<T: Driver>(KBox<UnsafeCell<bindings::cpufreq_driver>>, PhantomData<T>);
+
+/// SAFETY: `Registration` doesn't offer any methods or access to fields when shared between threads
+/// or CPUs, so it is safe to share it.
+unsafe impl<T: Driver> Sync for Registration<T> {}
+
+#[allow(clippy::non_send_fields_in_send_ty)]
+/// SAFETY: Registration with and unregistration from the cpufreq subsystem can happen from any
+/// thread.
+unsafe impl<T: Driver> Send for Registration<T> {}
+
+impl<T: Driver> Registration<T> {
+    const VTABLE: bindings::cpufreq_driver = bindings::cpufreq_driver {
+        name: Self::copy_name(T::NAME),
+        boost_enabled: T::BOOST_ENABLED,
+        flags: T::FLAGS,
+
+        // Initialize mandatory callbacks.
+        init: Some(Self::init_callback),
+        verify: Some(Self::verify_callback),
+
+        // Initialize optional callbacks based on the traits of `T`.
+        setpolicy: if T::HAS_SETPOLICY {
+            Some(Self::setpolicy_callback)
+        } else {
+            None
+        },
+        target: if T::HAS_TARGET {
+            Some(Self::target_callback)
+        } else {
+            None
+        },
+        target_index: if T::HAS_TARGET_INDEX {
+            Some(Self::target_index_callback)
+        } else {
+            None
+        },
+        fast_switch: if T::HAS_FAST_SWITCH {
+            Some(Self::fast_switch_callback)
+        } else {
+            None
+        },
+        adjust_perf: if T::HAS_ADJUST_PERF {
+            Some(Self::adjust_perf_callback)
+        } else {
+            None
+        },
+        get_intermediate: if T::HAS_GET_INTERMEDIATE {
+            Some(Self::get_intermediate_callback)
+        } else {
+            None
+        },
+        target_intermediate: if T::HAS_TARGET_INTERMEDIATE {
+            Some(Self::target_intermediate_callback)
+        } else {
+            None
+        },
+        get: if T::HAS_GET {
+            Some(Self::get_callback)
+        } else {
+            None
+        },
+        update_limits: if T::HAS_UPDATE_LIMITS {
+            Some(Self::update_limits_callback)
+        } else {
+            None
+        },
+        bios_limit: if T::HAS_BIOS_LIMIT {
+            Some(Self::bios_limit_callback)
+        } else {
+            None
+        },
+        online: if T::HAS_ONLINE {
+            Some(Self::online_callback)
+        } else {
+            None
+        },
+        offline: if T::HAS_OFFLINE {
+            Some(Self::offline_callback)
+        } else {
+            None
+        },
+        exit: if T::HAS_EXIT {
+            Some(Self::exit_callback)
+        } else {
+            None
+        },
+        suspend: if T::HAS_SUSPEND {
+            Some(Self::suspend_callback)
+        } else {
+            None
+        },
+        resume: if T::HAS_RESUME {
+            Some(Self::resume_callback)
+        } else {
+            None
+        },
+        ready: if T::HAS_READY {
+            Some(Self::ready_callback)
+        } else {
+            None
+        },
+        set_boost: if T::HAS_SET_BOOST {
+            Some(Self::set_boost_callback)
+        } else {
+            None
+        },
+        register_em: if T::HAS_REGISTER_EM {
+            Some(Self::register_em_callback)
+        } else {
+            None
+        },
+        // SAFETY: All zeros is a valid value for `bindings::cpufreq_driver`.
+        ..unsafe { MaybeUninit::zeroed().assume_init() }
+    };
+
+    const fn copy_name(name: &'static CStr) -> [c_char; CPUFREQ_NAME_LEN] {
+        let src = name.as_bytes_with_nul();
+        let mut dst = [0; CPUFREQ_NAME_LEN];
+
+        build_assert!(src.len() <= CPUFREQ_NAME_LEN);
+
+        let mut i = 0;
+        while i < src.len() {
+            dst[i] = src[i];
+            i += 1;
+        }
+
+        dst
+    }
+
+    /// Registers a CPU frequency driver with the cpufreq core.
+    pub fn new() -> Result<Self> {
+        // We can't use `&Self::VTABLE` directly because the cpufreq core modifies some fields in
+        // the C `struct cpufreq_driver`, which requires a mutable reference.
+        let mut drv = KBox::new(UnsafeCell::new(Self::VTABLE), GFP_KERNEL)?;
+
+        // SAFETY: `drv` is guaranteed to be valid for the lifetime of `Registration`.
+        to_result(unsafe { bindings::cpufreq_register_driver(drv.get_mut()) })?;
+
+        Ok(Self(drv, PhantomData))
+    }
+
+    /// Same as [`Registration::new`], but does not return a [`Registration`] instance.
+    ///
+    /// Instead the [`Registration`] is owned by [`Devres`] and will be revoked / dropped, once the
+    /// device is detached.
+    pub fn new_foreign_owned(dev: &Device<Bound>) -> Result {
+        Devres::new_foreign_owned(dev, Self::new()?, GFP_KERNEL)
+    }
+}
+
+/// CPU frequency driver callbacks.
+impl<T: Driver> Registration<T> {
+    /// Driver's `init` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn init_callback(ptr: *mut bindings::cpufreq_policy) -> kernel::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+            // lifetime of `policy`.
+            let policy = unsafe { Policy::from_raw_mut(ptr) };
+
+            let data = T::init(policy)?;
+            policy.set_data(data)?;
+            Ok(0)
+        })
+    }
+
+    /// Driver's `exit` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn exit_callback(ptr: *mut bindings::cpufreq_policy) {
+        // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+        // lifetime of `policy`.
+        let policy = unsafe { Policy::from_raw_mut(ptr) };
+
+        let data = policy.clear_data();
+        let _ = T::exit(policy, data);
+    }
+
+    /// Driver's `online` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn online_callback(ptr: *mut bindings::cpufreq_policy) -> kernel::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+            // lifetime of `policy`.
+            let policy = unsafe { Policy::from_raw_mut(ptr) };
+            T::online(policy).map(|()| 0)
+        })
+    }
+
+    /// Driver's `offline` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn offline_callback(ptr: *mut bindings::cpufreq_policy) -> kernel::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+            // lifetime of `policy`.
+            let policy = unsafe { Policy::from_raw_mut(ptr) };
+            T::offline(policy).map(|()| 0)
+        })
+    }
+
+    /// Driver's `suspend` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn suspend_callback(ptr: *mut bindings::cpufreq_policy) -> kernel::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+            // lifetime of `policy`.
+            let policy = unsafe { Policy::from_raw_mut(ptr) };
+            T::suspend(policy).map(|()| 0)
+        })
+    }
+
+    /// Driver's `resume` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn resume_callback(ptr: *mut bindings::cpufreq_policy) -> kernel::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+            // lifetime of `policy`.
+            let policy = unsafe { Policy::from_raw_mut(ptr) };
+            T::resume(policy).map(|()| 0)
+        })
+    }
+
+    /// Driver's `ready` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn ready_callback(ptr: *mut bindings::cpufreq_policy) {
+        // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+        // lifetime of `policy`.
+        let policy = unsafe { Policy::from_raw_mut(ptr) };
+        T::ready(policy);
+    }
+
+    /// Driver's `verify` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn verify_callback(ptr: *mut bindings::cpufreq_policy_data) -> kernel::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+            // lifetime of `policy`.
+            let data = unsafe { PolicyData::from_raw_mut(ptr) };
+            T::verify(data).map(|()| 0)
+        })
+    }
+
+    /// Driver's `setpolicy` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn setpolicy_callback(ptr: *mut bindings::cpufreq_policy) -> kernel::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+            // lifetime of `policy`.
+            let policy = unsafe { Policy::from_raw_mut(ptr) };
+            T::setpolicy(policy).map(|()| 0)
+        })
+    }
+
+    /// Driver's `target` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn target_callback(
+        ptr: *mut bindings::cpufreq_policy,
+        target_freq: u32,
+        relation: u32,
+    ) -> kernel::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+            // lifetime of `policy`.
+            let policy = unsafe { Policy::from_raw_mut(ptr) };
+            T::target(policy, target_freq, Relation::new(relation)?).map(|()| 0)
+        })
+    }
+
+    /// Driver's `target_index` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn target_index_callback(
+        ptr: *mut bindings::cpufreq_policy,
+        index: u32,
+    ) -> kernel::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+            // lifetime of `policy`.
+            let policy = unsafe { Policy::from_raw_mut(ptr) };
+
+            // SAFETY: The C code guarantees that `index` corresponds to a valid entry in the
+            // frequency table.
+            let index = unsafe { TableIndex::new(index as usize) };
+
+            T::target_index(policy, index).map(|()| 0)
+        })
+    }
+
+    /// Driver's `fast_switch` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn fast_switch_callback(
+        ptr: *mut bindings::cpufreq_policy,
+        target_freq: u32,
+    ) -> kernel::ffi::c_uint {
+        // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+        // lifetime of `policy`.
+        let policy = unsafe { Policy::from_raw_mut(ptr) };
+        T::fast_switch(policy, target_freq)
+    }
+
+    /// Driver's `adjust_perf` callback.
+    extern "C" fn adjust_perf_callback(
+        cpu: u32,
+        min_perf: usize,
+        target_perf: usize,
+        capacity: usize,
+    ) {
+        if let Ok(mut policy) = PolicyCpu::from_cpu(cpu) {
+            T::adjust_perf(&mut policy, min_perf, target_perf, capacity);
+        }
+    }
+
+    /// Driver's `get_intermediate` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn get_intermediate_callback(
+        ptr: *mut bindings::cpufreq_policy,
+        index: u32,
+    ) -> kernel::ffi::c_uint {
+        // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+        // lifetime of `policy`.
+        let policy = unsafe { Policy::from_raw_mut(ptr) };
+
+        // SAFETY: The C code guarantees that `index` corresponds to a valid entry in the
+        // frequency table.
+        let index = unsafe { TableIndex::new(index as usize) };
+
+        T::get_intermediate(policy, index)
+    }
+
+    /// Driver's `target_intermediate` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn target_intermediate_callback(
+        ptr: *mut bindings::cpufreq_policy,
+        index: u32,
+    ) -> kernel::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+            // lifetime of `policy`.
+            let policy = unsafe { Policy::from_raw_mut(ptr) };
+
+            // SAFETY: The C code guarantees that `index` corresponds to a valid entry in the
+            // frequency table.
+            let index = unsafe { TableIndex::new(index as usize) };
+
+            T::target_intermediate(policy, index).map(|()| 0)
+        })
+    }
+
+    /// Driver's `get` callback.
+    extern "C" fn get_callback(cpu: u32) -> kernel::ffi::c_uint {
+        PolicyCpu::from_cpu(cpu).map_or(0, |mut policy| T::get(&mut policy).map_or(0, |f| f))
+    }
+
+    /// Driver's `update_limit` callback.
+    extern "C" fn update_limits_callback(ptr: *mut bindings::cpufreq_policy) {
+        // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+        // lifetime of `policy`.
+        let policy = unsafe { Policy::from_raw_mut(ptr) };
+        T::update_limits(policy);
+    }
+
+    /// Driver's `bios_limit` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn bios_limit_callback(cpu: i32, limit: *mut u32) -> kernel::ffi::c_int {
+        from_result(|| {
+            let mut policy = PolicyCpu::from_cpu(cpu as u32)?;
+
+            // SAFETY: `limit` is guaranteed by the C code to be valid.
+            T::bios_limit(&mut policy, &mut (unsafe { *limit })).map(|()| 0)
+        })
+    }
+
+    /// Driver's `set_boost` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn set_boost_callback(
+        ptr: *mut bindings::cpufreq_policy,
+        state: i32,
+    ) -> kernel::ffi::c_int {
+        from_result(|| {
+            // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+            // lifetime of `policy`.
+            let policy = unsafe { Policy::from_raw_mut(ptr) };
+            T::set_boost(policy, state).map(|()| 0)
+        })
+    }
+
+    /// Driver's `register_em` callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn register_em_callback(ptr: *mut bindings::cpufreq_policy) {
+        // SAFETY: The `ptr` is guaranteed to be valid by the contract with the C code for the
+        // lifetime of `policy`.
+        let policy = unsafe { Policy::from_raw_mut(ptr) };
+        T::register_em(policy);
+    }
+}
+
+impl<T: Driver> Drop for Registration<T> {
+    /// Unregisters with the cpufreq core.
+    fn drop(&mut self) {
+        // SAFETY: `self.0` is guaranteed to be valid for the lifetime of `Registration`.
+        unsafe { bindings::cpufreq_unregister_driver(self.0.get_mut()) };
+    }
+}

rust/kernel/cpumask.rs

···
+// SPDX-License-Identifier: GPL-2.0
+
+//! CPU Mask abstractions.
+//!
+//! C header: [`include/linux/cpumask.h`](srctree/include/linux/cpumask.h)
+
+use crate::{
+    alloc::{AllocError, Flags},
+    prelude::*,
+    types::Opaque,
+};
+
+#[cfg(CONFIG_CPUMASK_OFFSTACK)]
+use core::ptr::{self, NonNull};
+
+#[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
+use core::mem::MaybeUninit;
+
+use core::ops::{Deref, DerefMut};
+
+/// A CPU Mask.
+///
+/// Rust abstraction for the C `struct cpumask`.
+///
+/// # Invariants
+///
+/// A [`Cpumask`] instance always corresponds to a valid C `struct cpumask`.
+///
+/// The callers must ensure that the `struct cpumask` is valid for access and
+/// remains valid for the lifetime of the returned reference.
+///
+/// ## Examples
+///
+/// The following example demonstrates how to update a [`Cpumask`].
+///
+/// ```
+/// use kernel::bindings;
+/// use kernel::cpumask::Cpumask;
+///
+/// fn set_clear_cpu(ptr: *mut bindings::cpumask, set_cpu: u32, clear_cpu: i32) {
+///     // SAFETY: The `ptr` is valid for writing and remains valid for the lifetime of the
+///     // returned reference.
+///     let mask = unsafe { Cpumask::as_mut_ref(ptr) };
+///
+///     mask.set(set_cpu);
+///     mask.clear(clear_cpu);
+/// }
+/// ```
+#[repr(transparent)]
+pub struct Cpumask(Opaque<bindings::cpumask>);
+
+impl Cpumask {
+    /// Creates a mutable reference to an existing `struct cpumask` pointer.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that `ptr` is valid for writing and remains valid for the lifetime
+    /// of the returned reference.
+    pub unsafe fn as_mut_ref<'a>(ptr: *mut bindings::cpumask) -> &'a mut Self {
+        // SAFETY: Guaranteed by the safety requirements of the function.
+        //
+        // INVARIANT: The caller ensures that `ptr` is valid for writing and remains valid for the
+        // lifetime of the returned reference.
+        unsafe { &mut *ptr.cast() }
+    }
+
+    /// Creates a reference to an existing `struct cpumask` pointer.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that `ptr` is valid for reading and remains valid for the lifetime
+    /// of the returned reference.
+    pub unsafe fn as_ref<'a>(ptr: *const bindings::cpumask) -> &'a Self {
+        // SAFETY: Guaranteed by the safety requirements of the function.
+        //
+        // INVARIANT: The caller ensures that `ptr` is valid for reading and remains valid for the
+        // lifetime of the returned reference.
+        unsafe { &*ptr.cast() }
+    }
+
+    /// Obtain the raw `struct cpumask` pointer.
+    pub fn as_raw(&self) -> *mut bindings::cpumask {
+        let this: *const Self = self;
+        this.cast_mut().cast()
+    }
+
+    /// Set `cpu` in the cpumask.
+    ///
+    /// ATTENTION: Contrary to C, this Rust `set()` method is non-atomic.
+    /// This mismatches kernel naming convention and corresponds to the C
+    /// function `__cpumask_set_cpu()`.
+    #[inline]
+    pub fn set(&mut self, cpu: u32) {
+        // SAFETY: By the type invariant, `self.as_raw` is a valid argument to `__cpumask_set_cpu`.
+        unsafe { bindings::__cpumask_set_cpu(cpu, self.as_raw()) };
+    }
+
+    /// Clear `cpu` in the cpumask.
+    ///
+    /// ATTENTION: Contrary to C, this Rust `clear()` method is non-atomic.
+    /// This mismatches kernel naming convention and corresponds to the C
+    /// function `__cpumask_clear_cpu()`.
+    #[inline]
+    pub fn clear(&mut self, cpu: i32) {
+        // SAFETY: By the type invariant, `self.as_raw` is a valid argument to
+        // `__cpumask_clear_cpu`.
+        unsafe { bindings::__cpumask_clear_cpu(cpu, self.as_raw()) };
+    }
+
+    /// Test `cpu` in the cpumask.
+    ///
+    /// Equivalent to the kernel's `cpumask_test_cpu` API.
+    #[inline]
+    pub fn test(&self, cpu: i32) -> bool {
+        // SAFETY: By the type invariant, `self.as_raw` is a valid argument to `cpumask_test_cpu`.
+        unsafe { bindings::cpumask_test_cpu(cpu, self.as_raw()) }
+    }
+
+    /// Set all CPUs in the cpumask.
+    ///
+    /// Equivalent to the kernel's `cpumask_setall` API.
+    #[inline]
+    pub fn setall(&mut self) {
+        // SAFETY: By the type invariant, `self.as_raw` is a valid argument to `cpumask_setall`.
+        unsafe { bindings::cpumask_setall(self.as_raw()) };
+    }
+
+    /// Checks if cpumask is empty.
+    ///
+    /// Equivalent to the kernel's `cpumask_empty` API.
+    #[inline]
+    pub fn empty(&self) -> bool {
+        // SAFETY: By the type invariant, `self.as_raw` is a valid argument to `cpumask_empty`.
+        unsafe { bindings::cpumask_empty(self.as_raw()) }
+    }
+
+    /// Checks if cpumask is full.
+    ///
+    /// Equivalent to the kernel's `cpumask_full` API.
+    #[inline]
+    pub fn full(&self) -> bool {
+        // SAFETY: By the type invariant, `self.as_raw` is a valid argument to `cpumask_full`.
+        unsafe { bindings::cpumask_full(self.as_raw()) }
+    }
+
+    /// Get weight of the cpumask.
+    ///
+    /// Equivalent to the kernel's `cpumask_weight` API.
+    #[inline]
+    pub fn weight(&self) -> u32 {
+        // SAFETY: By the type invariant, `self.as_raw` is a valid argument to `cpumask_weight`.
+        unsafe { bindings::cpumask_weight(self.as_raw()) }
+    }
+
+    /// Copy cpumask.
+    ///
+    /// Equivalent to the kernel's `cpumask_copy` API.
+    #[inline]
+    pub fn copy(&self, dstp: &mut Self) {
+        // SAFETY: By the type invariant, `Self::as_raw` is a valid argument to `cpumask_copy`.
+        unsafe { bindings::cpumask_copy(dstp.as_raw(), self.as_raw()) };
+    }
+}
+
+/// A CPU Mask pointer.
+///
+/// Rust abstraction for the C `struct cpumask_var_t`.
+///
+/// # Invariants
+///
+/// A [`CpumaskVar`] instance always corresponds to a valid C `struct cpumask_var_t`.
+///
+/// The callers must ensure that the `struct cpumask_var_t` is valid for access and remains valid
+/// for the lifetime of [`CpumaskVar`].
+///
+/// ## Examples
+///
+/// The following example demonstrates how to create and update a [`CpumaskVar`].
+///
+/// ```
+/// use kernel::cpumask::CpumaskVar;
+///
+/// let mut mask = CpumaskVar::new_zero(GFP_KERNEL).unwrap();
+///
+/// assert!(mask.empty());
+/// mask.set(2);
+/// assert!(mask.test(2));
+/// mask.set(3);
+/// assert!(mask.test(3));
+/// assert_eq!(mask.weight(), 2);
+///
+/// let mask2 = CpumaskVar::try_clone(&mask).unwrap();
+/// assert!(mask2.test(2));
+/// assert!(mask2.test(3));
+/// assert_eq!(mask2.weight(), 2);
+/// ```
+pub struct CpumaskVar {
+    #[cfg(CONFIG_CPUMASK_OFFSTACK)]
+    ptr: NonNull<Cpumask>,
+    #[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
+    mask: Cpumask,
+}
+
+impl CpumaskVar {
+    /// Creates a zero-initialized instance of the [`CpumaskVar`].
+    pub fn new_zero(_flags: Flags) -> Result<Self, AllocError> {
+        Ok(Self {
+            #[cfg(CONFIG_CPUMASK_OFFSTACK)]
+            ptr: {
+                let mut ptr: *mut bindings::cpumask = ptr::null_mut();
+
+                // SAFETY: It is safe to call this method as the reference to `ptr` is valid.
+                //
+                // INVARIANT: The associated memory is freed when the `CpumaskVar` goes out of
+                // scope.
+                unsafe { bindings::zalloc_cpumask_var(&mut ptr, _flags.as_raw()) };
+                NonNull::new(ptr.cast()).ok_or(AllocError)?
+            },
+
+            #[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
+            // SAFETY: FFI type is valid to be zero-initialized.
+            //
+            // INVARIANT: The associated memory is freed when the `CpumaskVar` goes out of scope.
+            mask: unsafe { core::mem::zeroed() },
+        })
+    }
+
+    /// Creates an instance of the [`CpumaskVar`].
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that the returned [`CpumaskVar`] is properly initialized before
+    /// getting used.
+    pub unsafe fn new(_flags: Flags) -> Result<Self, AllocError> {
+        Ok(Self {
+            #[cfg(CONFIG_CPUMASK_OFFSTACK)]
+            ptr: {
+                let mut ptr: *mut bindings::cpumask = ptr::null_mut();
+
+                // SAFETY: It is safe to call this method as the reference to `ptr` is valid.
+                //
+                // INVARIANT: The associated memory is freed when the `CpumaskVar` goes out of
+                // scope.
+                unsafe { bindings::alloc_cpumask_var(&mut ptr, _flags.as_raw()) };
+                NonNull::new(ptr.cast()).ok_or(AllocError)?
+            },
+            #[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
+            // SAFETY: Guaranteed by the safety requirements of the function.
+            //
+            // INVARIANT: The associated memory is freed when the `CpumaskVar` goes out of scope.
+            mask: unsafe { MaybeUninit::uninit().assume_init() },
+        })
+    }
+
+    /// Creates a mutable reference to an existing `struct cpumask_var_t` pointer.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that `ptr` is valid for writing and remains valid for the lifetime
+    /// of the returned reference.
+    pub unsafe fn as_mut_ref<'a>(ptr: *mut bindings::cpumask_var_t) -> &'a mut Self {
+        // SAFETY: Guaranteed by the safety requirements of the function.
+        //
+        // INVARIANT: The caller ensures that `ptr` is valid for writing and remains valid for the
+        // lifetime of the returned reference.
+        unsafe { &mut *ptr.cast() }
+    }
+
+    /// Creates a reference to an existing `struct cpumask_var_t` pointer.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that `ptr` is valid for reading and remains valid for the lifetime
+    /// of the returned reference.
+    pub unsafe fn as_ref<'a>(ptr: *const bindings::cpumask_var_t) -> &'a Self {
+        // SAFETY: Guaranteed by the safety requirements of the function.
+        //
+        // INVARIANT: The caller ensures that `ptr` is valid for reading and remains valid for the
+        // lifetime of the returned reference.
+        unsafe { &*ptr.cast() }
+    }
+
+    /// Clones cpumask.
+    pub fn try_clone(cpumask: &Cpumask) -> Result<Self> {
+        // SAFETY: The returned cpumask_var is initialized right after this call.
+        let mut cpumask_var = unsafe { Self::new(GFP_KERNEL) }?;
+
+        cpumask.copy(&mut cpumask_var);
+        Ok(cpumask_var)
+    }
+}
+
+// Make [`CpumaskVar`] behave like a pointer to [`Cpumask`].
+impl Deref for CpumaskVar {
+    type Target = Cpumask;
+
+    #[cfg(CONFIG_CPUMASK_OFFSTACK)]
+    fn deref(&self) -> &Self::Target {
+        // SAFETY: The caller owns CpumaskVar, so it is safe to deref the cpumask.
+        unsafe { &*self.ptr.as_ptr() }
+    }
+
+    #[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
+    fn deref(&self) -> &Self::Target {
+        &self.mask
+    }
+}
+
+impl DerefMut for CpumaskVar {
+    #[cfg(CONFIG_CPUMASK_OFFSTACK)]
+    fn deref_mut(&mut self) -> &mut Cpumask {
+        // SAFETY: The caller owns CpumaskVar, so it is safe to deref the cpumask.
+        unsafe { self.ptr.as_mut() }
+    }
+
+    #[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
+    fn deref_mut(&mut self) -> &mut Cpumask {
+        &mut self.mask
+    }
+}
+
+impl Drop for CpumaskVar {
+    fn drop(&mut self) {
+        #[cfg(CONFIG_CPUMASK_OFFSTACK)]
+        // SAFETY: By the type invariant, `self.as_raw` is a valid argument to `free_cpumask_var`.
+        unsafe {
+            bindings::free_cpumask_var(self.as_raw())
+        };
+    }
+}

rust/kernel/device.rs

···
     str::CStr,
     types::{ARef, Opaque},
 };
-use core::{fmt, ptr};
+use core::{fmt, marker::PhantomData, ptr};
 
 #[cfg(CONFIG_PRINTK)]
 use crate::c_str;
···
 /// `bindings::device::release` is valid to be called from any thread, hence `ARef<Device>` can be
 /// dropped from any thread.
 #[repr(transparent)]
-pub struct Device(Opaque<bindings::device>);
+pub struct Device<Ctx: DeviceContext = Normal>(Opaque<bindings::device>, PhantomData<Ctx>);
 
 impl Device {
     /// Creates a new reference-counted abstraction instance of an existing `struct device` pointer.
···
         // SAFETY: By the safety requirements ptr is valid
         unsafe { Self::as_ref(ptr) }.into()
     }
+}
 
+impl<Ctx: DeviceContext> Device<Ctx> {
     /// Obtain the raw `struct device *`.
     pub(crate) fn as_raw(&self) -> *mut bindings::device {
         self.0.get()
···
     }
 }
 
+// SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic
+// argument.
+kernel::impl_device_context_deref!(unsafe { Device });
+kernel::impl_device_context_into_aref!(Device);
+
 // SAFETY: Instances of `Device` are always reference-counted.
 unsafe impl crate::types::AlwaysRefCounted for Device {
     fn inc_ref(&self) {
···
 /// any of the bus callbacks, such as `probe()`.
 pub struct Core;
 
+/// The [`Bound`] context is the context of a bus specific device reference when it is guaranteed to
+/// be bound for the duration of its lifetime.
+pub struct Bound;
+
 mod private {
     pub trait Sealed {}
 
+    impl Sealed for super::Bound {}
     impl Sealed for super::Core {}
     impl Sealed for super::Normal {}
 }
 
+impl DeviceContext for Bound {}
 impl DeviceContext for Core {}
 impl DeviceContext for Normal {}
+
+/// # Safety
+///
+/// The type given as `$device` must be a transparent wrapper of a type that doesn't depend on the
+/// generic argument of `$device`.
+#[doc(hidden)]
+#[macro_export]
+macro_rules! __impl_device_context_deref {
+    (unsafe { $device:ident, $src:ty => $dst:ty }) => {
+        impl ::core::ops::Deref for $device<$src> {
+            type Target = $device<$dst>;
+
+            fn deref(&self) -> &Self::Target {
+                let ptr: *const Self = self;
+
+                // CAST: `$device<$src>` and `$device<$dst>` transparently wrap the same type by the
+                // safety requirement of the macro.
+                let ptr = ptr.cast::<Self::Target>();
+
+                // SAFETY: `ptr` was derived from `&self`.
+                unsafe { &*ptr }
+            }
+        }
+    };
+}
+
+/// Implement [`core::ops::Deref`] traits for allowed [`DeviceContext`] conversions of a (bus
+/// specific) device.
+///
+/// # Safety
+///
+/// The type given as `$device` must be a transparent wrapper of a type that doesn't depend on the
+/// generic argument of `$device`.
+#[macro_export]
+macro_rules! impl_device_context_deref {
+    (unsafe { $device:ident }) => {
+        // SAFETY: This macro has the exact same safety requirement as
+        // `__impl_device_context_deref!`.
+        ::kernel::__impl_device_context_deref!(unsafe {
+            $device,
+            $crate::device::Core => $crate::device::Bound
+        });
+
+        // SAFETY: This macro has the exact same safety requirement as
+        // `__impl_device_context_deref!`.
+        ::kernel::__impl_device_context_deref!(unsafe {
+            $device,
+            $crate::device::Bound => $crate::device::Normal
+        });
+    };
+}
+
+#[doc(hidden)]
+#[macro_export]
+macro_rules! __impl_device_context_into_aref {
+    ($src:ty, $device:tt) => {
+        impl ::core::convert::From<&$device<$src>> for $crate::types::ARef<$device> {
+            fn from(dev: &$device<$src>) -> Self {
+                (&**dev).into()
+            }
+        }
+    };
+}
+
+/// Implement [`core::convert::From`], such that all `&Device<Ctx>` can be converted to an
+/// `ARef<Device>`.
+#[macro_export]
+macro_rules! impl_device_context_into_aref {
+    ($device:tt) => {
+        ::kernel::__impl_device_context_into_aref!($crate::device::Core, $device);
+        ::kernel::__impl_device_context_into_aref!($crate::device::Bound, $device);
+    };
+}
 
 #[doc(hidden)]
 #[macro_export]

rust/kernel/devres.rs

···
 use crate::{
     alloc::Flags,
     bindings,
-    device::Device,
+    device::{Bound, Device},
     error::{Error, Result},
     ffi::c_void,
     prelude::*,
···
 /// # Example
 ///
 /// ```no_run
-/// # use kernel::{bindings, c_str, device::Device, devres::Devres, io::{Io, IoRaw}};
+/// # use kernel::{bindings, c_str, device::{Bound, Device}, devres::Devres, io::{Io, IoRaw}};
 /// # use core::ops::Deref;
 ///
 /// // See also [`pci::Bar`] for a real example.
···
 ///         unsafe { Io::from_raw(&self.0) }
 ///    }
 /// }
-/// # fn no_run() -> Result<(), Error> {
-/// # // SAFETY: Invalid usage; just for the example to get an `ARef<Device>` instance.
-/// # let dev = unsafe { Device::get_device(core::ptr::null_mut()) };
-///
+/// # fn no_run(dev: &Device<Bound>) -> Result<(), Error> {
 /// // SAFETY: Invalid usage for example purposes.
 /// let iomem = unsafe { IoMem::<{ core::mem::size_of::<u32>() }>::new(0xBAAAAAAD)? };
-/// let devres = Devres::new(&dev, iomem, GFP_KERNEL)?;
+/// let devres = Devres::new(dev, iomem, GFP_KERNEL)?;
 ///
 /// let res = devres.try_access().ok_or(ENXIO)?;
 /// res.write8(0x42, 0x0);
···
 pub struct Devres<T>(Arc<DevresInner<T>>);
 
 impl<T> DevresInner<T> {
-    fn new(dev: &Device, data: T, flags: Flags) -> Result<Arc<DevresInner<T>>> {
+    fn new(dev: &Device<Bound>, data: T, flags: Flags) -> Result<Arc<DevresInner<T>>> {
         let inner = Arc::pin_init(
             pin_init!( DevresInner {
                 dev: dev.into(),
···
 impl<T> Devres<T> {
     /// Creates a new [`Devres`] instance of the given `data`. The `data` encapsulated within the
     /// returned `Devres` instance' `data` will be revoked once the device is detached.
-    pub fn new(dev: &Device, data: T, flags: Flags) -> Result<Self> {
+    pub fn new(dev: &Device<Bound>, data: T, flags: Flags) -> Result<Self> {
         let inner = DevresInner::new(dev, data, flags)?;
 
         Ok(Devres(inner))
···
 
     /// Same as [`Devres::new`], but does not return a `Devres` instance. Instead the given `data`
     /// is owned by devres and will be revoked / dropped, once the device is detached.
-    pub fn new_foreign_owned(dev: &Device, data: T, flags: Flags) -> Result {
+    pub fn new_foreign_owned(dev: &Device<Bound>, data: T, flags: Flags) -> Result {
         let _ = DevresInner::new(dev, data, flags)?;
 
         Ok(())

rust/kernel/lib.rs

···
 pub mod block;
 #[doc(hidden)]
 pub mod build_assert;
+pub mod clk;
+pub mod cpu;
+#[cfg(CONFIG_CPU_FREQ)]
+pub mod cpufreq;
+pub mod cpumask;
 pub mod cred;
 pub mod device;
 pub mod device_id;
···
 #[cfg(CONFIG_NET)]
 pub mod net;
 pub mod of;
+#[cfg(CONFIG_PM_OPP)]
+pub mod opp;
 pub mod page;
 #[cfg(CONFIG_PCI)]
 pub mod pci;

rust/kernel/opp.rs

···
+// SPDX-License-Identifier: GPL-2.0
+
+//! Operating performance points.
+//!
+//! This module provides rust abstractions for interacting with the OPP subsystem.
+//!
+//! C header: [`include/linux/pm_opp.h`](srctree/include/linux/pm_opp.h)
+//!
+//! Reference: <https://docs.kernel.org/power/opp.html>
+
+use crate::{
+    clk::Hertz,
+    cpumask::{Cpumask, CpumaskVar},
+    device::Device,
+    error::{code::*, from_err_ptr, from_result, to_result, Error, Result, VTABLE_DEFAULT_ERROR},
+    ffi::c_ulong,
+    prelude::*,
+    str::CString,
+    types::{ARef, AlwaysRefCounted, Opaque},
+};
+
+#[cfg(CONFIG_CPU_FREQ)]
+/// Frequency table implementation.
+mod freq {
+    use super::*;
+    use crate::cpufreq;
+    use core::ops::Deref;
+
+    /// OPP frequency table.
+    ///
+    /// A [`cpufreq::Table`] created from [`Table`].
+    pub struct FreqTable {
+        dev: ARef<Device>,
+        ptr: *mut bindings::cpufreq_frequency_table,
+    }
+
+    impl FreqTable {
+        /// Creates a new instance of [`FreqTable`] from [`Table`].
+        pub(crate) fn new(table: &Table) -> Result<Self> {
+            let mut ptr: *mut bindings::cpufreq_frequency_table = ptr::null_mut();
+
+            // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+            // requirements.
+            to_result(unsafe {
+                bindings::dev_pm_opp_init_cpufreq_table(table.dev.as_raw(), &mut ptr)
+            })?;
+
+            Ok(Self {
+                dev: table.dev.clone(),
+                ptr,
+            })
+        }
+
+        /// Returns a reference to the underlying [`cpufreq::Table`].
+        #[inline]
+        fn table(&self) -> &cpufreq::Table {
+            // SAFETY: The `ptr` is guaranteed by the C code to be valid.
+            unsafe { cpufreq::Table::from_raw(self.ptr) }
+        }
+    }
+
+    impl Deref for FreqTable {
+        type Target = cpufreq::Table;
+
+        #[inline]
+        fn deref(&self) -> &Self::Target {
+            self.table()
+        }
+    }
+
+    impl Drop for FreqTable {
+        fn drop(&mut self) {
+            // SAFETY: The pointer was created via `dev_pm_opp_init_cpufreq_table`, and is only
+            // freed here.
+            unsafe {
+                bindings::dev_pm_opp_free_cpufreq_table(self.dev.as_raw(), &mut self.as_raw())
+            };
+        }
+    }
+}
+
+#[cfg(CONFIG_CPU_FREQ)]
+pub use freq::FreqTable;
+
+use core::{marker::PhantomData, ptr};
+
+use macros::vtable;
+
+/// Creates a null-terminated slice of pointers to [`Cstring`]s.
+fn to_c_str_array(names: &[CString]) -> Result<KVec<*const u8>> {
+    // Allocated a null-terminated vector of pointers.
+    let mut list = KVec::with_capacity(names.len() + 1, GFP_KERNEL)?;
+
+    for name in names.iter() {
+        list.push(name.as_ptr() as _, GFP_KERNEL)?;
+    }
+
+    list.push(ptr::null(), GFP_KERNEL)?;
+    Ok(list)
+}
+
+/// The voltage unit.
+///
+/// Represents voltage in microvolts, wrapping a [`c_ulong`] value.
+///
+/// ## Examples
+///
+/// ```
+/// use kernel::opp::MicroVolt;
+///
+/// let raw = 90500;
+/// let volt = MicroVolt(raw);
+///
+/// assert_eq!(usize::from(volt), raw);
+/// assert_eq!(volt, MicroVolt(raw));
+/// ```
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub struct MicroVolt(pub c_ulong);
+
+impl From<MicroVolt> for c_ulong {
+    #[inline]
+    fn from(volt: MicroVolt) -> Self {
+        volt.0
+    }
+}
+
+/// The power unit.
+///
+/// Represents power in microwatts, wrapping a [`c_ulong`] value.
+///
+/// ## Examples
+///
+/// ```
+/// use kernel::opp::MicroWatt;
+///
+/// let raw = 1000000;
+/// let power = MicroWatt(raw);
+///
+/// assert_eq!(usize::from(power), raw);
+/// assert_eq!(power, MicroWatt(raw));
+/// ```
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub struct MicroWatt(pub c_ulong);
+
+impl From<MicroWatt> for c_ulong {
+    #[inline]
+    fn from(power: MicroWatt) -> Self {
+        power.0
+    }
+}
+
+/// Handle for a dynamically created [`OPP`].
+///
+/// The associated [`OPP`] is automatically removed when the [`Token`] is dropped.
+///
+/// ## Examples
+///
+/// The following example demonstrates how to create an [`OPP`] dynamically.
+///
+/// ```
+/// use kernel::clk::Hertz;
+/// use kernel::device::Device;
+/// use kernel::error::Result;
+/// use kernel::opp::{Data, MicroVolt, Token};
+/// use kernel::types::ARef;
+///
+/// fn create_opp(dev: &ARef<Device>, freq: Hertz, volt: MicroVolt, level: u32) -> Result<Token> {
+///     let data = Data::new(freq, volt, level, false);
+///
+///     // OPP is removed once token goes out of scope.
+///     data.add_opp(dev)
+/// }
+/// ```
+pub struct Token {
+    dev: ARef<Device>,
+    freq: Hertz,
+}
+
+impl Token {
+    /// Dynamically adds an [`OPP`] and returns a [`Token`] that removes it on drop.
+    fn new(dev: &ARef<Device>, mut data: Data) -> Result<Self> {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe { bindings::dev_pm_opp_add_dynamic(dev.as_raw(), &mut data.0) })?;
+        Ok(Self {
+            dev: dev.clone(),
+            freq: data.freq(),
+        })
+    }
+}
+
+impl Drop for Token {
+    fn drop(&mut self) {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        unsafe { bindings::dev_pm_opp_remove(self.dev.as_raw(), self.freq.into()) };
+    }
+}
+
+/// OPP data.
+///
+/// Rust abstraction for the C `struct dev_pm_opp_data`, used to define operating performance
+/// points (OPPs) dynamically.
+///
+/// ## Examples
+///
+/// The following example demonstrates how to create an [`OPP`] with [`Data`].
+///
+/// ```
+/// use kernel::clk::Hertz;
+/// use kernel::device::Device;
+/// use kernel::error::Result;
+/// use kernel::opp::{Data, MicroVolt, Token};
+/// use kernel::types::ARef;
+///
+/// fn create_opp(dev: &ARef<Device>, freq: Hertz, volt: MicroVolt, level: u32) -> Result<Token> {
+///     let data = Data::new(freq, volt, level, false);
+///
+///     // OPP is removed once token goes out of scope.
+///     data.add_opp(dev)
+/// }
+/// ```
+#[repr(transparent)]
+pub struct Data(bindings::dev_pm_opp_data);
+
+impl Data {
+    /// Creates a new instance of [`Data`].
+    ///
+    /// This can be used to define a dynamic OPP to be added to a device.
+    pub fn new(freq: Hertz, volt: MicroVolt, level: u32, turbo: bool) -> Self {
+        Self(bindings::dev_pm_opp_data {
+            turbo,
+            freq: freq.into(),
+            u_volt: volt.into(),
+            level,
+        })
+    }
+
+    /// Adds an [`OPP`] dynamically.
+    ///
+    /// Returns a [`Token`] that ensures the OPP is automatically removed
+    /// when it goes out of scope.
+    #[inline]
+    pub fn add_opp(self, dev: &ARef<Device>) -> Result<Token> {
+        Token::new(dev, self)
+    }
+
+    /// Returns the frequency associated with this OPP data.
+    #[inline]
+    fn freq(&self) -> Hertz {
+        Hertz(self.0.freq)
+    }
+}
+
+/// [`OPP`] search options.
+///
+/// ## Examples
+///
+/// Defines how to search for an [`OPP`] in a [`Table`] relative to a frequency.
+///
+/// ```
+/// use kernel::clk::Hertz;
+/// use kernel::error::Result;
+/// use kernel::opp::{OPP, SearchType, Table};
+/// use kernel::types::ARef;
+///
+/// fn find_opp(table: &Table, freq: Hertz) -> Result<ARef<OPP>> {
+///     let opp = table.opp_from_freq(freq, Some(true), None, SearchType::Exact)?;
+///
+///     pr_info!("OPP frequency is: {:?}\n", opp.freq(None));
+///     pr_info!("OPP voltage is: {:?}\n", opp.voltage());
+///     pr_info!("OPP level is: {}\n", opp.level());
+///     pr_info!("OPP power is: {:?}\n", opp.power());
+///
+///     Ok(opp)
+/// }
+/// ```
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub enum SearchType {
+    /// Match the exact frequency.
+    Exact,
+    /// Find the highest frequency less than or equal to the given value.
+    Floor,
+    /// Find the lowest frequency greater than or equal to the given value.
+    Ceil,
+}
+
+/// OPP configuration callbacks.
+///
+/// Implement this trait to customize OPP clock and regulator setup for your device.
+#[vtable]
+pub trait ConfigOps {
+    /// This is typically used to scale clocks when transitioning between OPPs.
+    #[inline]
+    fn config_clks(_dev: &Device, _table: &Table, _opp: &OPP, _scaling_down: bool) -> Result {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// This provides access to the old and new OPPs, allowing for safe regulator adjustments.
+    #[inline]
+    fn config_regulators(
+        _dev: &Device,
+        _opp_old: &OPP,
+        _opp_new: &OPP,
+        _data: *mut *mut bindings::regulator,
+        _count: u32,
+    ) -> Result {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+}
+
+/// OPP configuration token.
+///
+/// Returned by the OPP core when configuration is applied to a [`Device`]. The associated
+/// configuration is automatically cleared when the token is dropped.
+pub struct ConfigToken(i32);
+
+impl Drop for ConfigToken {
+    fn drop(&mut self) {
+        // SAFETY: This is the same token value returned by the C code via `dev_pm_opp_set_config`.
+        unsafe { bindings::dev_pm_opp_clear_config(self.0) };
+    }
+}
+
+/// OPP configurations.
+///
+/// Rust abstraction for the C `struct dev_pm_opp_config`.
+///
+/// ## Examples
+///
+/// The following example demonstrates how to set OPP property-name configuration for a [`Device`].
+///
+/// ```
+/// use kernel::device::Device;
+/// use kernel::error::Result;
+/// use kernel::opp::{Config, ConfigOps, ConfigToken};
+/// use kernel::str::CString;
+/// use kernel::types::ARef;
+/// use kernel::macros::vtable;
+///
+/// #[derive(Default)]
+/// struct Driver;
+///
+/// #[vtable]
+/// impl ConfigOps for Driver {}
+///
+/// fn configure(dev: &ARef<Device>) -> Result<ConfigToken> {
+///     let name = CString::try_from_fmt(fmt!("{}", "slow"))?;
+///
+///     // The OPP configuration is cleared once the [`ConfigToken`] goes out of scope.
+///     Config::<Driver>::new()
+///         .set_prop_name(name)?
+///         .set(dev)
+/// }
+/// ```
+#[derive(Default)]
+pub struct Config<T: ConfigOps>
+where
+    T: Default,
+{
+    clk_names: Option<KVec<CString>>,
+    prop_name: Option<CString>,
+    regulator_names: Option<KVec<CString>>,
+    supported_hw: Option<KVec<u32>>,
+
+    // Tuple containing (required device, index)
+    required_dev: Option<(ARef<Device>, u32)>,
+    _data: PhantomData<T>,
+}
+
+impl<T: ConfigOps + Default> Config<T> {
+    /// Creates a new instance of [`Config`].
+    #[inline]
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Initializes clock names.
+    pub fn set_clk_names(mut self, names: KVec<CString>) -> Result<Self> {
+        if self.clk_names.is_some() {
+            return Err(EBUSY);
+        }
+
+        if names.is_empty() {
+            return Err(EINVAL);
+        }
+
+        self.clk_names = Some(names);
+        Ok(self)
+    }
+
+    /// Initializes property name.
+    pub fn set_prop_name(mut self, name: CString) -> Result<Self> {
+        if self.prop_name.is_some() {
+            return Err(EBUSY);
+        }
+
+        self.prop_name = Some(name);
+        Ok(self)
+    }
+
+    /// Initializes regulator names.
+    pub fn set_regulator_names(mut self, names: KVec<CString>) -> Result<Self> {
+        if self.regulator_names.is_some() {
+            return Err(EBUSY);
+        }
+
+        if names.is_empty() {
+            return Err(EINVAL);
+        }
+
+        self.regulator_names = Some(names);
+
+        Ok(self)
+    }
+
+    /// Initializes required devices.
+    pub fn set_required_dev(mut self, dev: ARef<Device>, index: u32) -> Result<Self> {
+        if self.required_dev.is_some() {
+            return Err(EBUSY);
+        }
+
+        self.required_dev = Some((dev, index));
+        Ok(self)
+    }
+
+    /// Initializes supported hardware.
+    pub fn set_supported_hw(mut self, hw: KVec<u32>) -> Result<Self> {
+        if self.supported_hw.is_some() {
+            return Err(EBUSY);
+        }
+
+        if hw.is_empty() {
+            return Err(EINVAL);
+        }
+
+        self.supported_hw = Some(hw);
+        Ok(self)
+    }
+
+    /// Sets the configuration with the OPP core.
+    ///
+    /// The returned [`ConfigToken`] will remove the configuration when dropped.
+    pub fn set(self, dev: &Device) -> Result<ConfigToken> {
+        let (_clk_list, clk_names) = match &self.clk_names {
+            Some(x) => {
+                let list = to_c_str_array(x)?;
+                let ptr = list.as_ptr();
+                (Some(list), ptr)
+            }
+            None => (None, ptr::null()),
+        };
+
+        let (_regulator_list, regulator_names) = match &self.regulator_names {
+            Some(x) => {
+                let list = to_c_str_array(x)?;
+                let ptr = list.as_ptr();
+                (Some(list), ptr)
+            }
+            None => (None, ptr::null()),
+        };
+
+        let prop_name = self
+            .prop_name
+            .as_ref()
+            .map_or(ptr::null(), |p| p.as_char_ptr());
+
+        let (supported_hw, supported_hw_count) = self
+            .supported_hw
+            .as_ref()
+            .map_or((ptr::null(), 0), |hw| (hw.as_ptr(), hw.len() as u32));
+
+        let (required_dev, required_dev_index) = self
+            .required_dev
+            .as_ref()
+            .map_or((ptr::null_mut(), 0), |(dev, idx)| (dev.as_raw(), *idx));
+
+        let mut config = bindings::dev_pm_opp_config {
+            clk_names,
+            config_clks: if T::HAS_CONFIG_CLKS {
+                Some(Self::config_clks)
+            } else {
+                None
+            },
+            prop_name,
+            regulator_names,
+            config_regulators: if T::HAS_CONFIG_REGULATORS {
+                Some(Self::config_regulators)
+            } else {
+                None
+            },
+            supported_hw,
+            supported_hw_count,
+
+            required_dev,
+            required_dev_index,
+        };
+
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements. The OPP core guarantees not to access fields of [`Config`] after this call
+        // and so we don't need to save a copy of them for future use.
+        let ret = unsafe { bindings::dev_pm_opp_set_config(dev.as_raw(), &mut config) };
+        if ret < 0 {
+            Err(Error::from_errno(ret))
+        } else {
+            Ok(ConfigToken(ret))
+        }
+    }
+
+    /// Config's clk callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn config_clks(
+        dev: *mut bindings::device,
+        opp_table: *mut bindings::opp_table,
+        opp: *mut bindings::dev_pm_opp,
+        _data: *mut kernel::ffi::c_void,
+        scaling_down: bool,
+    ) -> kernel::ffi::c_int {
+        from_result(|| {
+            // SAFETY: 'dev' is guaranteed by the C code to be valid.
+            let dev = unsafe { Device::get_device(dev) };
+            T::config_clks(
+                &dev,
+                // SAFETY: 'opp_table' is guaranteed by the C code to be valid.
+                &unsafe { Table::from_raw_table(opp_table, &dev) },
+                // SAFETY: 'opp' is guaranteed by the C code to be valid.
+                unsafe { OPP::from_raw_opp(opp)? },
+                scaling_down,
+            )
+            .map(|()| 0)
+        })
+    }
+
+    /// Config's regulator callback.
+    ///
+    /// SAFETY: Called from C. Inputs must be valid pointers.
+    extern "C" fn config_regulators(
+        dev: *mut bindings::device,
+        old_opp: *mut bindings::dev_pm_opp,
+        new_opp: *mut bindings::dev_pm_opp,
+        regulators: *mut *mut bindings::regulator,
+        count: kernel::ffi::c_uint,
+    ) -> kernel::ffi::c_int {
+        from_result(|| {
+            // SAFETY: 'dev' is guaranteed by the C code to be valid.
+            let dev = unsafe { Device::get_device(dev) };
+            T::config_regulators(
+                &dev,
+                // SAFETY: 'old_opp' is guaranteed by the C code to be valid.
+                unsafe { OPP::from_raw_opp(old_opp)? },
+                // SAFETY: 'new_opp' is guaranteed by the C code to be valid.
+                unsafe { OPP::from_raw_opp(new_opp)? },
+                regulators,
+                count,
+            )
+            .map(|()| 0)
+        })
+    }
+}
+
+/// A reference-counted OPP table.
+///
+/// Rust abstraction for the C `struct opp_table`.
+///
+/// # Invariants
+///
+/// The pointer stored in `Self` is non-null and valid for the lifetime of the [`Table`].
+///
+/// Instances of this type are reference-counted.
+///
+/// ## Examples
+///
+/// The following example demonstrates how to get OPP [`Table`] for a [`Cpumask`] and set its
+/// frequency.
+///
+/// ```
+/// use kernel::clk::Hertz;
+/// use kernel::cpumask::Cpumask;
+/// use kernel::device::Device;
+/// use kernel::error::Result;
+/// use kernel::opp::Table;
+/// use kernel::types::ARef;
+///
+/// fn get_table(dev: &ARef<Device>, mask: &mut Cpumask, freq: Hertz) -> Result<Table> {
+///     let mut opp_table = Table::from_of_cpumask(dev, mask)?;
+///
+///     if opp_table.opp_count()? == 0 {
+///         return Err(EINVAL);
+///     }
+///
+///     pr_info!("Max transition latency is: {} ns\n", opp_table.max_transition_latency_ns());
+///     pr_info!("Suspend frequency is: {:?}\n", opp_table.suspend_freq());
+///
+///     opp_table.set_rate(freq)?;
+///     Ok(opp_table)
+/// }
+/// ```
+pub struct Table {
+    ptr: *mut bindings::opp_table,
+    dev: ARef<Device>,
+    #[allow(dead_code)]
+    em: bool,
+    #[allow(dead_code)]
+    of: bool,
+    cpus: Option<CpumaskVar>,
+}
+
+/// SAFETY: It is okay to send ownership of [`Table`] across thread boundaries.
+unsafe impl Send for Table {}
+
+/// SAFETY: It is okay to access [`Table`] through shared references from other threads because
+/// we're either accessing properties that don't change or that are properly synchronised by C code.
+unsafe impl Sync for Table {}
+
+impl Table {
+    /// Creates a new reference-counted [`Table`] from a raw pointer.
+    ///
+    /// # Safety
+    ///
+    /// Callers must ensure that `ptr` is valid and non-null.
+    unsafe fn from_raw_table(ptr: *mut bindings::opp_table, dev: &ARef<Device>) -> Self {
+        // SAFETY: By the safety requirements, ptr is valid and its refcount will be incremented.
+        //
+        // INVARIANT: The reference-count is decremented when [`Table`] goes out of scope.
+        unsafe { bindings::dev_pm_opp_get_opp_table_ref(ptr) };
+
+        Self {
+            ptr,
+            dev: dev.clone(),
+            em: false,
+            of: false,
+            cpus: None,
+        }
+    }
+
+    /// Creates a new reference-counted [`Table`] instance for a [`Device`].
+    pub fn from_dev(dev: &Device) -> Result<Self> {
+        // SAFETY: The requirements are satisfied by the existence of the [`Device`] and its safety
+        // requirements.
+        //
+        // INVARIANT: The reference-count is incremented by the C code and is decremented when
+        // [`Table`] goes out of scope.
+        let ptr = from_err_ptr(unsafe { bindings::dev_pm_opp_get_opp_table(dev.as_raw()) })?;
+
+        Ok(Self {
+            ptr,
+            dev: dev.into(),
+            em: false,
+            of: false,
+            cpus: None,
+        })
+    }
+
+    /// Creates a new reference-counted [`Table`] instance for a [`Device`] based on device tree
+    /// entries.
+    #[cfg(CONFIG_OF)]
+    pub fn from_of(dev: &ARef<Device>, index: i32) -> Result<Self> {
+        // SAFETY: The requirements are satisfied by the existence of the [`Device`] and its safety
+        // requirements.
+        //
+        // INVARIANT: The reference-count is incremented by the C code and is decremented when
+        // [`Table`] goes out of scope.
+        to_result(unsafe { bindings::dev_pm_opp_of_add_table_indexed(dev.as_raw(), index) })?;
+
+        // Get the newly created [`Table`].
+        let mut table = Self::from_dev(dev)?;
+        table.of = true;
+
+        Ok(table)
+    }
+
+    /// Remove device tree based [`Table`].
+    #[cfg(CONFIG_OF)]
+    #[inline]
+    fn remove_of(&self) {
+        // SAFETY: The requirements are satisfied by the existence of the [`Device`] and its safety
+        // requirements. We took the reference from [`from_of`] earlier, it is safe to drop the
+        // same now.
+        unsafe { bindings::dev_pm_opp_of_remove_table(self.dev.as_raw()) };
+    }
+
+    /// Creates a new reference-counted [`Table`] instance for a [`Cpumask`] based on device tree
+    /// entries.
+    #[cfg(CONFIG_OF)]
+    pub fn from_of_cpumask(dev: &Device, cpumask: &mut Cpumask) -> Result<Self> {
+        // SAFETY: The cpumask is valid and the returned pointer will be owned by the [`Table`]
+        // instance.
+        //
+        // INVARIANT: The reference-count is incremented by the C code and is decremented when
+        // [`Table`] goes out of scope.
+        to_result(unsafe { bindings::dev_pm_opp_of_cpumask_add_table(cpumask.as_raw()) })?;
+
+        // Fetch the newly created table.
+        let mut table = Self::from_dev(dev)?;
+        table.cpus = Some(CpumaskVar::try_clone(cpumask)?);
+
+        Ok(table)
+    }
+
+    /// Remove device tree based [`Table`] for a [`Cpumask`].
+    #[cfg(CONFIG_OF)]
+    #[inline]
+    fn remove_of_cpumask(&self, cpumask: &Cpumask) {
+        // SAFETY: The cpumask is valid and we took the reference from [`from_of_cpumask`] earlier,
+        // it is safe to drop the same now.
+        unsafe { bindings::dev_pm_opp_of_cpumask_remove_table(cpumask.as_raw()) };
+    }
+
+    /// Returns the number of [`OPP`]s in the [`Table`].
+    pub fn opp_count(&self) -> Result<u32> {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        let ret = unsafe { bindings::dev_pm_opp_get_opp_count(self.dev.as_raw()) };
+        if ret < 0 {
+            Err(Error::from_errno(ret))
+        } else {
+            Ok(ret as u32)
+        }
+    }
+
+    /// Returns max clock latency (in nanoseconds) of the [`OPP`]s in the [`Table`].
+    #[inline]
+    pub fn max_clock_latency_ns(&self) -> usize {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        unsafe { bindings::dev_pm_opp_get_max_clock_latency(self.dev.as_raw()) }
+    }
+
+    /// Returns max volt latency (in nanoseconds) of the [`OPP`]s in the [`Table`].
+    #[inline]
+    pub fn max_volt_latency_ns(&self) -> usize {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        unsafe { bindings::dev_pm_opp_get_max_volt_latency(self.dev.as_raw()) }
+    }
+
+    /// Returns max transition latency (in nanoseconds) of the [`OPP`]s in the [`Table`].
+    #[inline]
+    pub fn max_transition_latency_ns(&self) -> usize {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        unsafe { bindings::dev_pm_opp_get_max_transition_latency(self.dev.as_raw()) }
+    }
+
+    /// Returns the suspend [`OPP`]'s frequency.
+    #[inline]
+    pub fn suspend_freq(&self) -> Hertz {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        Hertz(unsafe { bindings::dev_pm_opp_get_suspend_opp_freq(self.dev.as_raw()) })
+    }
+
+    /// Synchronizes regulators used by the [`Table`].
+    #[inline]
+    pub fn sync_regulators(&self) -> Result {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe { bindings::dev_pm_opp_sync_regulators(self.dev.as_raw()) })
+    }
+
+    /// Gets sharing CPUs.
+    #[inline]
+    pub fn sharing_cpus(dev: &Device, cpumask: &mut Cpumask) -> Result {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe { bindings::dev_pm_opp_get_sharing_cpus(dev.as_raw(), cpumask.as_raw()) })
+    }
+
+    /// Sets sharing CPUs.
+    pub fn set_sharing_cpus(&mut self, cpumask: &mut Cpumask) -> Result {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe {
+            bindings::dev_pm_opp_set_sharing_cpus(self.dev.as_raw(), cpumask.as_raw())
+        })?;
+
+        if let Some(mask) = self.cpus.as_mut() {
+            // Update the cpumask as this will be used while removing the table.
+            cpumask.copy(mask);
+        }
+
+        Ok(())
+    }
+
+    /// Gets sharing CPUs from device tree.
+    #[cfg(CONFIG_OF)]
+    #[inline]
+    pub fn of_sharing_cpus(dev: &Device, cpumask: &mut Cpumask) -> Result {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe {
+            bindings::dev_pm_opp_of_get_sharing_cpus(dev.as_raw(), cpumask.as_raw())
+        })
+    }
+
+    /// Updates the voltage value for an [`OPP`].
+    #[inline]
+    pub fn adjust_voltage(
+        &self,
+        freq: Hertz,
+        volt: MicroVolt,
+        volt_min: MicroVolt,
+        volt_max: MicroVolt,
+    ) -> Result {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe {
+            bindings::dev_pm_opp_adjust_voltage(
+                self.dev.as_raw(),
+                freq.into(),
+                volt.into(),
+                volt_min.into(),
+                volt_max.into(),
+            )
+        })
+    }
+
+    /// Creates [`FreqTable`] from [`Table`].
+    #[cfg(CONFIG_CPU_FREQ)]
+    #[inline]
+    pub fn cpufreq_table(&mut self) -> Result<FreqTable> {
+        FreqTable::new(self)
+    }
+
+    /// Configures device with [`OPP`] matching the frequency value.
+    #[inline]
+    pub fn set_rate(&self, freq: Hertz) -> Result {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe { bindings::dev_pm_opp_set_rate(self.dev.as_raw(), freq.into()) })
+    }
+
+    /// Configures device with [`OPP`].
+    #[inline]
+    pub fn set_opp(&self, opp: &OPP) -> Result {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe { bindings::dev_pm_opp_set_opp(self.dev.as_raw(), opp.as_raw()) })
+    }
+
+    /// Finds [`OPP`] based on frequency.
+    pub fn opp_from_freq(
+        &self,
+        freq: Hertz,
+        available: Option<bool>,
+        index: Option<u32>,
+        stype: SearchType,
+    ) -> Result<ARef<OPP>> {
+        let raw_dev = self.dev.as_raw();
+        let index = index.unwrap_or(0);
+        let mut rate = freq.into();
+
+        let ptr = from_err_ptr(match stype {
+            SearchType::Exact => {
+                if let Some(available) = available {
+                    // SAFETY: The requirements are satisfied by the existence of [`Device`] and
+                    // its safety requirements. The returned pointer will be owned by the new
+                    // [`OPP`] instance.
+                    unsafe {
+                        bindings::dev_pm_opp_find_freq_exact_indexed(
+                            raw_dev, rate, index, available,
+                        )
+                    }
+                } else {
+                    return Err(EINVAL);
+                }
+            }
+
+            // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+            // requirements. The returned pointer will be owned by the new [`OPP`] instance.
+            SearchType::Ceil => unsafe {
+                bindings::dev_pm_opp_find_freq_ceil_indexed(raw_dev, &mut rate, index)
+            },
+
+            // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+            // requirements. The returned pointer will be owned by the new [`OPP`] instance.
+            SearchType::Floor => unsafe {
+                bindings::dev_pm_opp_find_freq_floor_indexed(raw_dev, &mut rate, index)
+            },
+        })?;
+
+        // SAFETY: The `ptr` is guaranteed by the C code to be valid.
+        unsafe { OPP::from_raw_opp_owned(ptr) }
+    }
+
+    /// Finds [`OPP`] based on level.
+    pub fn opp_from_level(&self, mut level: u32, stype: SearchType) -> Result<ARef<OPP>> {
+        let raw_dev = self.dev.as_raw();
+
+        let ptr = from_err_ptr(match stype {
+            // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+            // requirements. The returned pointer will be owned by the new [`OPP`] instance.
+            SearchType::Exact => unsafe { bindings::dev_pm_opp_find_level_exact(raw_dev, level) },
+
+            // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+            // requirements. The returned pointer will be owned by the new [`OPP`] instance.
+            SearchType::Ceil => unsafe {
+                bindings::dev_pm_opp_find_level_ceil(raw_dev, &mut level)
+            },
+
+            // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+            // requirements. The returned pointer will be owned by the new [`OPP`] instance.
+            SearchType::Floor => unsafe {
+                bindings::dev_pm_opp_find_level_floor(raw_dev, &mut level)
+            },
+        })?;
+
+        // SAFETY: The `ptr` is guaranteed by the C code to be valid.
+        unsafe { OPP::from_raw_opp_owned(ptr) }
+    }
+
+    /// Finds [`OPP`] based on bandwidth.
+    pub fn opp_from_bw(&self, mut bw: u32, index: i32, stype: SearchType) -> Result<ARef<OPP>> {
+        let raw_dev = self.dev.as_raw();
+
+        let ptr = from_err_ptr(match stype {
+            // The OPP core doesn't support this yet.
+            SearchType::Exact => return Err(EINVAL),
+
+            // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+            // requirements. The returned pointer will be owned by the new [`OPP`] instance.
+            SearchType::Ceil => unsafe {
+                bindings::dev_pm_opp_find_bw_ceil(raw_dev, &mut bw, index)
+            },
+
+            // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+            // requirements. The returned pointer will be owned by the new [`OPP`] instance.
+            SearchType::Floor => unsafe {
+                bindings::dev_pm_opp_find_bw_floor(raw_dev, &mut bw, index)
+            },
+        })?;
+
+        // SAFETY: The `ptr` is guaranteed by the C code to be valid.
+        unsafe { OPP::from_raw_opp_owned(ptr) }
+    }
+
+    /// Enables the [`OPP`].
+    #[inline]
+    pub fn enable_opp(&self, freq: Hertz) -> Result {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe { bindings::dev_pm_opp_enable(self.dev.as_raw(), freq.into()) })
+    }
+
+    /// Disables the [`OPP`].
+    #[inline]
+    pub fn disable_opp(&self, freq: Hertz) -> Result {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe { bindings::dev_pm_opp_disable(self.dev.as_raw(), freq.into()) })
+    }
+
+    /// Registers with the Energy model.
+    #[cfg(CONFIG_OF)]
+    pub fn of_register_em(&mut self, cpumask: &mut Cpumask) -> Result {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe {
+            bindings::dev_pm_opp_of_register_em(self.dev.as_raw(), cpumask.as_raw())
+        })?;
+
+        self.em = true;
+        Ok(())
+    }
+
+    /// Unregisters with the Energy model.
+    #[cfg(all(CONFIG_OF, CONFIG_ENERGY_MODEL))]
+    #[inline]
+    fn of_unregister_em(&self) {
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements. We registered with the EM framework earlier, it is safe to unregister now.
+        unsafe { bindings::em_dev_unregister_perf_domain(self.dev.as_raw()) };
+    }
+}
+
+impl Drop for Table {
+    fn drop(&mut self) {
+        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe
+        // to relinquish it now.
+        unsafe { bindings::dev_pm_opp_put_opp_table(self.ptr) };
+
+        #[cfg(CONFIG_OF)]
+        {
+            #[cfg(CONFIG_ENERGY_MODEL)]
+            if self.em {
+                self.of_unregister_em();
+            }
+
+            if self.of {
+                self.remove_of();
+            } else if let Some(cpumask) = self.cpus.take() {
+                self.remove_of_cpumask(&cpumask);
+            }
+        }
+    }
+}
+
+/// A reference-counted Operating performance point (OPP).
+///
+/// Rust abstraction for the C `struct dev_pm_opp`.
+///
+/// # Invariants
+///
+/// The pointer stored in `Self` is non-null and valid for the lifetime of the [`OPP`].
+///
+/// Instances of this type are reference-counted. The reference count is incremented by the
+/// `dev_pm_opp_get` function and decremented by `dev_pm_opp_put`. The Rust type `ARef<OPP>`
+/// represents a pointer that owns a reference count on the [`OPP`].
+///
+/// A reference to the [`OPP`], &[`OPP`], isn't refcounted by the Rust code.
+///
+/// ## Examples
+///
+/// The following example demonstrates how to get [`OPP`] corresponding to a frequency value and
+/// configure the device with it.
+///
+/// ```
+/// use kernel::clk::Hertz;
+/// use kernel::error::Result;
+/// use kernel::opp::{SearchType, Table};
+///
+/// fn configure_opp(table: &Table, freq: Hertz) -> Result {
+///     let opp = table.opp_from_freq(freq, Some(true), None, SearchType::Exact)?;
+///
+///     if opp.freq(None) != freq {
+///         return Err(EINVAL);
+///     }
+///
+///     table.set_opp(&opp)
+/// }
+/// ```
+#[repr(transparent)]
+pub struct OPP(Opaque<bindings::dev_pm_opp>);
+
+/// SAFETY: It is okay to send the ownership of [`OPP`] across thread boundaries.
+unsafe impl Send for OPP {}
+
+/// SAFETY: It is okay to access [`OPP`] through shared references from other threads because we're
+/// either accessing properties that don't change or that are properly synchronised by C code.
+unsafe impl Sync for OPP {}
+
+/// SAFETY: The type invariants guarantee that [`OPP`] is always refcounted.
+unsafe impl AlwaysRefCounted for OPP {
+    fn inc_ref(&self) {
+        // SAFETY: The existence of a shared reference means that the refcount is nonzero.
+        unsafe { bindings::dev_pm_opp_get(self.0.get()) };
+    }
+
+    unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
+        // SAFETY: The safety requirements guarantee that the refcount is nonzero.
+        unsafe { bindings::dev_pm_opp_put(obj.cast().as_ptr()) }
+    }
+}
+
+impl OPP {
+    /// Creates an owned reference to a [`OPP`] from a valid pointer.
+    ///
+    /// The refcount is incremented by the C code and will be decremented by `dec_ref` when the
+    /// [`ARef`] object is dropped.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that `ptr` is valid and the refcount of the [`OPP`] is incremented.
+    /// The caller must also ensure that it doesn't explicitly drop the refcount of the [`OPP`], as
+    /// the returned [`ARef`] object takes over the refcount increment on the underlying object and
+    /// the same will be dropped along with it.
+    pub unsafe fn from_raw_opp_owned(ptr: *mut bindings::dev_pm_opp) -> Result<ARef<Self>> {
+        let ptr = ptr::NonNull::new(ptr).ok_or(ENODEV)?;
+
+        // SAFETY: The safety requirements guarantee the validity of the pointer.
+        //
+        // INVARIANT: The reference-count is decremented when [`OPP`] goes out of scope.
+        Ok(unsafe { ARef::from_raw(ptr.cast()) })
+    }
+
+    /// Creates a reference to a [`OPP`] from a valid pointer.
+    ///
+    /// The refcount is not updated by the Rust API unless the returned reference is converted to
+    /// an [`ARef`] object.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that `ptr` is valid and remains valid for the duration of `'a`.
+    #[inline]
+    pub unsafe fn from_raw_opp<'a>(ptr: *mut bindings::dev_pm_opp) -> Result<&'a Self> {
+        // SAFETY: The caller guarantees that the pointer is not dangling and stays valid for the
+        // duration of 'a. The cast is okay because [`OPP`] is `repr(transparent)`.
+        Ok(unsafe { &*ptr.cast() })
+    }
+
+    #[inline]
+    fn as_raw(&self) -> *mut bindings::dev_pm_opp {
+        self.0.get()
+    }
+
+    /// Returns the frequency of an [`OPP`].
+    pub fn freq(&self, index: Option<u32>) -> Hertz {
+        let index = index.unwrap_or(0);
+
+        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
+        // use it.
+        Hertz(unsafe { bindings::dev_pm_opp_get_freq_indexed(self.as_raw(), index) })
+    }
+
+    /// Returns the voltage of an [`OPP`].
+    #[inline]
+    pub fn voltage(&self) -> MicroVolt {
+        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
+        // use it.
+        MicroVolt(unsafe { bindings::dev_pm_opp_get_voltage(self.as_raw()) })
+    }
+
+    /// Returns the level of an [`OPP`].
+    #[inline]
+    pub fn level(&self) -> u32 {
+        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
+        // use it.
+        unsafe { bindings::dev_pm_opp_get_level(self.as_raw()) }
+    }
+
+    /// Returns the power of an [`OPP`].
+    #[inline]
+    pub fn power(&self) -> MicroWatt {
+        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
+        // use it.
+        MicroWatt(unsafe { bindings::dev_pm_opp_get_power(self.as_raw()) })
+    }
+
+    /// Returns the required pstate of an [`OPP`].
+    #[inline]
+    pub fn required_pstate(&self, index: u32) -> u32 {
+        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
+        // use it.
+        unsafe { bindings::dev_pm_opp_get_required_pstate(self.as_raw(), index) }
+    }
+
+    /// Returns true if the [`OPP`] is turbo.
+    #[inline]
+    pub fn is_turbo(&self) -> bool {
+        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
+        // use it.
+        unsafe { bindings::dev_pm_opp_is_turbo(self.as_raw()) }
+    }
+}

rust/kernel/pci.rs

···
     }
 }
 
-impl Device {
+impl<Ctx: device::DeviceContext> Device<Ctx> {
     fn as_raw(&self) -> *mut bindings::pci_dev {
         self.0.get()
     }
+}
 
+impl Device {
     /// Returns the PCI vendor ID.
     pub fn vendor_id(&self) -> u16 {
         // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
···
         // - by its type invariant `self.as_raw` is always a valid pointer to a `struct pci_dev`.
         Ok(unsafe { bindings::pci_resource_len(self.as_raw(), bar.try_into()?) })
     }
+}
 
+impl Device<device::Bound> {
     /// Mapps an entire PCI-BAR after performing a region-request on it. I/O operation bound checks
     /// can be performed on compile time for offsets (plus the requested type size) < SIZE.
     pub fn iomap_region_sized<const SIZE: usize>(
···
     }
 }
 
-impl Deref for Device<device::Core> {
-    type Target = Device;
-
-    fn deref(&self) -> &Self::Target {
-        let ptr: *const Self = self;
-
-        // CAST: `Device<Ctx>` is a transparent wrapper of `Opaque<bindings::pci_dev>`.
-        let ptr = ptr.cast::<Device>();
-
-        // SAFETY: `ptr` was derived from `&self`.
-        unsafe { &*ptr }
-    }
-}
-
-impl From<&Device<device::Core>> for ARef<Device> {
-    fn from(dev: &Device<device::Core>) -> Self {
-        (&**dev).into()
-    }
-}
+// SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic
+// argument.
+kernel::impl_device_context_deref!(unsafe { Device });
+kernel::impl_device_context_into_aref!(Device);
 
 // SAFETY: Instances of `Device` are always reference-counted.
 unsafe impl crate::types::AlwaysRefCounted for Device {
···
     }
 }
 
-impl AsRef<device::Device> for Device {
-    fn as_ref(&self) -> &device::Device {
+impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
+    fn as_ref(&self) -> &device::Device<Ctx> {
         // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
         // `struct pci_dev`.
         let dev = unsafe { addr_of_mut!((*self.as_raw()).dev) };

rust/kernel/platform.rs

···
     of,
     prelude::*,
     str::CStr,
-    types::{ARef, ForeignOwnable, Opaque},
+    types::{ForeignOwnable, Opaque},
     ThisModule,
 };
 
 use core::{
     marker::PhantomData,
-    ops::Deref,
     ptr::{addr_of_mut, NonNull},
 };
 
···
     PhantomData<Ctx>,
 );
 
-impl Device {
+impl<Ctx: device::DeviceContext> Device<Ctx> {
     fn as_raw(&self) -> *mut bindings::platform_device {
         self.0.get()
     }
 }
 
-impl Deref for Device<device::Core> {
-    type Target = Device;
-
-    fn deref(&self) -> &Self::Target {
-        let ptr: *const Self = self;
-
-        // CAST: `Device<Ctx>` is a transparent wrapper of `Opaque<bindings::platform_device>`.
-        let ptr = ptr.cast::<Device>();
-
-        // SAFETY: `ptr` was derived from `&self`.
-        unsafe { &*ptr }
-    }
-}
-
-impl From<&Device<device::Core>> for ARef<Device> {
-    fn from(dev: &Device<device::Core>) -> Self {
-        (&**dev).into()
-    }
-}
+// SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic
+// argument.
+kernel::impl_device_context_deref!(unsafe { Device });
+kernel::impl_device_context_into_aref!(Device);
 
 // SAFETY: Instances of `Device` are always reference-counted.
 unsafe impl crate::types::AlwaysRefCounted for Device {
···
     }
 }
 
-impl AsRef<device::Device> for Device {
-    fn as_ref(&self) -> &device::Device {
+impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
+    fn as_ref(&self) -> &device::Device<Ctx> {
         // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
         // `struct platform_device`.
         let dev = unsafe { addr_of_mut!((*self.as_raw()).dev) };

rust/macros/module.rs

···
 
     let info = ModuleInfo::parse(&mut it);
 
-    let mut modinfo = ModInfoBuilder::new(info.name.as_ref());
+    // Rust does not allow hyphens in identifiers, use underscore instead.
+    let ident = info.name.replace('-', "_");
+    let mut modinfo = ModInfoBuilder::new(ident.as_ref());
     if let Some(author) = info.author {
         modinfo.emit("author", &author);
     }
···
                     #[doc(hidden)]
                     #[link_section = \"{initcall_section}\"]
                     #[used]
-                    pub static __{name}_initcall: extern \"C\" fn() -> kernel::ffi::c_int = __{name}_init;
+                    pub static __{ident}_initcall: extern \"C\" fn() ->
+                        kernel::ffi::c_int = __{ident}_init;
 
                     #[cfg(not(MODULE))]
                     #[cfg(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS)]
                     core::arch::global_asm!(
                         r#\".section \"{initcall_section}\", \"a\"
-                        __{name}_initcall:
-                            .long   __{name}_init - .
+                        __{ident}_initcall:
+                            .long   __{ident}_init - .
                             .previous
                         \"#
                     );
···
                     #[cfg(not(MODULE))]
                     #[doc(hidden)]
                     #[no_mangle]
-                    pub extern \"C\" fn __{name}_init() -> kernel::ffi::c_int {{
+                    pub extern \"C\" fn __{ident}_init() -> kernel::ffi::c_int {{
                         // SAFETY: This function is inaccessible to the outside due to the double
                         // module wrapping it. It is called exactly once by the C side via its
                         // placement above in the initcall section.
···
                     #[cfg(not(MODULE))]
                     #[doc(hidden)]
                     #[no_mangle]
-                    pub extern \"C\" fn __{name}_exit() {{
+                    pub extern \"C\" fn __{ident}_exit() {{
                         // SAFETY:
                         // - This function is inaccessible to the outside due to the double
                         //   module wrapping it. It is called exactly once by the C side via its
                         //   unique name,
-                        // - furthermore it is only called after `__{name}_init` has returned `0`
-                        //   (which delegates to `__init`).
+                        // - furthermore it is only called after `__{ident}_init` has
+                        //   returned `0` (which delegates to `__init`).
                         unsafe {{ __exit() }}
                     }}
 
···
         ",
         type_ = info.type_,
         name = info.name,
+        ident = ident,
         modinfo = modinfo.buffer,
         initcall_section = ".initcall6.init"
     )