PowerCap: Add class driver

The power capping framework providing a consistent interface between the
kernel and user space that allows power capping drivers to expose their
settings to user space in a uniform way.
The overall design of the framework is described in the documentation
added by the previous patch in this series.

Signed-off-by: Srinivas Pandruvada <[e-mail]>
Signed-off-by: Jacob Pan <[e-mail]>
Reviewed-by: Rafael J. Wysocki <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/powercap/Kconfig

···
+#
+# Generic power capping sysfs interface configuration
+#
+
+menuconfig POWERCAP
+	bool "Generic powercap sysfs driver"
+	help
+	  The power capping sysfs interface allows kernel subsystems to expose power
+	  capping settings to user space in a consistent way.  Usually, it consists
+	  of multiple control types that determine which settings may be exposed and
+	  power zones representing parts of the system that can be subject to power
+	  capping.
+
+	  If you want this code to be compiled in, say Y here.
+
+if POWERCAP
+# Client driver configurations go here.
+
+endif

drivers/powercap/Makefile

···
+obj-$(CONFIG_POWERCAP)	+= powercap_sys.o

drivers/powercap/powercap_sys.c

···
+/*
+ * Power capping class
+ * Copyright (c) 2013, Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/powercap.h>
+
+#define to_powercap_zone(n) container_of(n, struct powercap_zone, dev)
+#define to_powercap_control_type(n) \
+			container_of(n, struct powercap_control_type, dev)
+
+/* Power zone show function */
+#define define_power_zone_show(_attr)		\
+static ssize_t _attr##_show(struct device *dev, \
+					struct device_attribute *dev_attr,\
+					char *buf) \
+{ \
+	u64 value; \
+	ssize_t len = -EINVAL; \
+	struct powercap_zone *power_zone = to_powercap_zone(dev); \
+	\
+	if (power_zone->ops->get_##_attr) { \
+		if (!power_zone->ops->get_##_attr(power_zone, &value)) \
+			len = sprintf(buf, "%lld\n", value); \
+	} \
+	\
+	return len; \
+}
+
+/* The only meaningful input is 0 (reset), others are silently ignored */
+#define define_power_zone_store(_attr)		\
+static ssize_t _attr##_store(struct device *dev,\
+				struct device_attribute *dev_attr, \
+				const char *buf, size_t count) \
+{ \
+	int err; \
+	struct powercap_zone *power_zone = to_powercap_zone(dev); \
+	u64 value; \
+	\
+	err = kstrtoull(buf, 10, &value); \
+	if (err) \
+		return -EINVAL; \
+	if (value) \
+		return count; \
+	if (power_zone->ops->reset_##_attr) { \
+		if (!power_zone->ops->reset_##_attr(power_zone)) \
+			return count; \
+	} \
+	\
+	return -EINVAL; \
+}
+
+/* Power zone constraint show function */
+#define define_power_zone_constraint_show(_attr) \
+static ssize_t show_constraint_##_attr(struct device *dev, \
+				struct device_attribute *dev_attr,\
+				char *buf) \
+{ \
+	u64 value; \
+	ssize_t len = -ENODATA; \
+	struct powercap_zone *power_zone = to_powercap_zone(dev); \
+	int id; \
+	struct powercap_zone_constraint *pconst;\
+	\
+	if (!sscanf(dev_attr->attr.name, "constraint_%d_", &id)) \
+		return -EINVAL; \
+	if (id >= power_zone->const_id_cnt)	\
+		return -EINVAL; \
+	pconst = &power_zone->constraints[id]; \
+	if (pconst && pconst->ops && pconst->ops->get_##_attr) { \
+		if (!pconst->ops->get_##_attr(power_zone, id, &value)) \
+			len = sprintf(buf, "%lld\n", value); \
+	} \
+	\
+	return len; \
+}
+
+/* Power zone constraint store function */
+#define define_power_zone_constraint_store(_attr) \
+static ssize_t store_constraint_##_attr(struct device *dev,\
+				struct device_attribute *dev_attr, \
+				const char *buf, size_t count) \
+{ \
+	int err; \
+	u64 value; \
+	struct powercap_zone *power_zone = to_powercap_zone(dev); \
+	int id; \
+	struct powercap_zone_constraint *pconst;\
+	\
+	if (!sscanf(dev_attr->attr.name, "constraint_%d_", &id)) \
+		return -EINVAL; \
+	if (id >= power_zone->const_id_cnt)	\
+		return -EINVAL; \
+	pconst = &power_zone->constraints[id]; \
+	err = kstrtoull(buf, 10, &value); \
+	if (err) \
+		return -EINVAL; \
+	if (pconst && pconst->ops && pconst->ops->set_##_attr) { \
+		if (!pconst->ops->set_##_attr(power_zone, id, value)) \
+			return count; \
+	} \
+	\
+	return -ENODATA; \
+}
+
+/* Power zone information callbacks */
+define_power_zone_show(power_uw);
+define_power_zone_show(max_power_range_uw);
+define_power_zone_show(energy_uj);
+define_power_zone_store(energy_uj);
+define_power_zone_show(max_energy_range_uj);
+
+/* Power zone attributes */
+static DEVICE_ATTR_RO(max_power_range_uw);
+static DEVICE_ATTR_RO(power_uw);
+static DEVICE_ATTR_RO(max_energy_range_uj);
+static DEVICE_ATTR_RW(energy_uj);
+
+/* Power zone constraint attributes callbacks */
+define_power_zone_constraint_show(power_limit_uw);
+define_power_zone_constraint_store(power_limit_uw);
+define_power_zone_constraint_show(time_window_us);
+define_power_zone_constraint_store(time_window_us);
+define_power_zone_constraint_show(max_power_uw);
+define_power_zone_constraint_show(min_power_uw);
+define_power_zone_constraint_show(max_time_window_us);
+define_power_zone_constraint_show(min_time_window_us);
+
+/* For one time seeding of constraint device attributes */
+struct powercap_constraint_attr {
+	struct device_attribute power_limit_attr;
+	struct device_attribute time_window_attr;
+	struct device_attribute max_power_attr;
+	struct device_attribute min_power_attr;
+	struct device_attribute max_time_window_attr;
+	struct device_attribute min_time_window_attr;
+	struct device_attribute name_attr;
+};
+
+static struct powercap_constraint_attr
+				constraint_attrs[MAX_CONSTRAINTS_PER_ZONE];
+
+/* A list of powercap control_types */
+static LIST_HEAD(powercap_cntrl_list);
+/* Mutex to protect list of powercap control_types */
+static DEFINE_MUTEX(powercap_cntrl_list_lock);
+
+#define POWERCAP_CONSTRAINT_NAME_LEN	30 /* Some limit to avoid overflow */
+static ssize_t show_constraint_name(struct device *dev,
+				struct device_attribute *dev_attr,
+				char *buf)
+{
+	const char *name;
+	struct powercap_zone *power_zone = to_powercap_zone(dev);
+	int id;
+	ssize_t len = -ENODATA;
+	struct powercap_zone_constraint *pconst;
+
+	if (!sscanf(dev_attr->attr.name, "constraint_%d_", &id))
+		return -EINVAL;
+	if (id >= power_zone->const_id_cnt)
+		return -EINVAL;
+	pconst = &power_zone->constraints[id];
+
+	if (pconst && pconst->ops && pconst->ops->get_name) {
+		name = pconst->ops->get_name(power_zone, id);
+		if (name) {
+			snprintf(buf, POWERCAP_CONSTRAINT_NAME_LEN,
+								"%s\n", name);
+			buf[POWERCAP_CONSTRAINT_NAME_LEN] = '\0';
+			len = strlen(buf);
+		}
+	}
+
+	return len;
+}
+
+static int create_constraint_attribute(int id, const char *name,
+				int mode,
+				struct device_attribute *dev_attr,
+				ssize_t (*show)(struct device *,
+					struct device_attribute *, char *),
+				ssize_t (*store)(struct device *,
+					struct device_attribute *,
+				const char *, size_t)
+				)
+{
+
+	dev_attr->attr.name = kasprintf(GFP_KERNEL, "constraint_%d_%s",
+								id, name);
+	if (!dev_attr->attr.name)
+		return -ENOMEM;
+	dev_attr->attr.mode = mode;
+	dev_attr->show = show;
+	dev_attr->store = store;
+
+	return 0;
+}
+
+static void free_constraint_attributes(void)
+{
+	int i;
+
+	for (i = 0; i < MAX_CONSTRAINTS_PER_ZONE; ++i) {
+		kfree(constraint_attrs[i].power_limit_attr.attr.name);
+		kfree(constraint_attrs[i].time_window_attr.attr.name);
+		kfree(constraint_attrs[i].name_attr.attr.name);
+		kfree(constraint_attrs[i].max_power_attr.attr.name);
+		kfree(constraint_attrs[i].min_power_attr.attr.name);
+		kfree(constraint_attrs[i].max_time_window_attr.attr.name);
+		kfree(constraint_attrs[i].min_time_window_attr.attr.name);
+	}
+}
+
+static int seed_constraint_attributes(void)
+{
+	int i;
+	int ret;
+
+	for (i = 0; i < MAX_CONSTRAINTS_PER_ZONE; ++i) {
+		ret = create_constraint_attribute(i, "power_limit_uw",
+					S_IWUSR | S_IRUGO,
+					&constraint_attrs[i].power_limit_attr,
+					show_constraint_power_limit_uw,
+					store_constraint_power_limit_uw);
+		if (ret)
+			goto err_alloc;
+		ret = create_constraint_attribute(i, "time_window_us",
+					S_IWUSR | S_IRUGO,
+					&constraint_attrs[i].time_window_attr,
+					show_constraint_time_window_us,
+					store_constraint_time_window_us);
+		if (ret)
+			goto err_alloc;
+		ret = create_constraint_attribute(i, "name", S_IRUGO,
+				&constraint_attrs[i].name_attr,
+				show_constraint_name,
+				NULL);
+		if (ret)
+			goto err_alloc;
+		ret = create_constraint_attribute(i, "max_power_uw", S_IRUGO,
+				&constraint_attrs[i].max_power_attr,
+				show_constraint_max_power_uw,
+				NULL);
+		if (ret)
+			goto err_alloc;
+		ret = create_constraint_attribute(i, "min_power_uw", S_IRUGO,
+				&constraint_attrs[i].min_power_attr,
+				show_constraint_min_power_uw,
+				NULL);
+		if (ret)
+			goto err_alloc;
+		ret = create_constraint_attribute(i, "max_time_window_us",
+				S_IRUGO,
+				&constraint_attrs[i].max_time_window_attr,
+				show_constraint_max_time_window_us,
+				NULL);
+		if (ret)
+			goto err_alloc;
+		ret = create_constraint_attribute(i, "min_time_window_us",
+				S_IRUGO,
+				&constraint_attrs[i].min_time_window_attr,
+				show_constraint_min_time_window_us,
+				NULL);
+		if (ret)
+			goto err_alloc;
+
+	}
+
+	return 0;
+
+err_alloc:
+	free_constraint_attributes();
+
+	return ret;
+}
+
+static int create_constraints(struct powercap_zone *power_zone,
+				int nr_constraints,
+				struct powercap_zone_constraint_ops *const_ops)
+{
+	int i;
+	int ret = 0;
+	int count;
+	struct powercap_zone_constraint *pconst;
+
+	if (!power_zone || !const_ops || !const_ops->get_power_limit_uw ||
+					!const_ops->set_power_limit_uw ||
+					!const_ops->get_time_window_us ||
+					!const_ops->set_time_window_us)
+		return -EINVAL;
+
+	count = power_zone->zone_attr_count;
+	for (i = 0; i < nr_constraints; ++i) {
+		pconst = &power_zone->constraints[i];
+		pconst->ops = const_ops;
+		pconst->id = power_zone->const_id_cnt;
+		power_zone->const_id_cnt++;
+		power_zone->zone_dev_attrs[count++] =
+				&constraint_attrs[i].power_limit_attr.attr;
+		power_zone->zone_dev_attrs[count++] =
+				&constraint_attrs[i].time_window_attr.attr;
+		if (pconst->ops->get_name)
+			power_zone->zone_dev_attrs[count++] =
+				&constraint_attrs[i].name_attr.attr;
+		if (pconst->ops->get_max_power_uw)
+			power_zone->zone_dev_attrs[count++] =
+				&constraint_attrs[i].max_power_attr.attr;
+		if (pconst->ops->get_min_power_uw)
+			power_zone->zone_dev_attrs[count++] =
+				&constraint_attrs[i].min_power_attr.attr;
+		if (pconst->ops->get_max_time_window_us)
+			power_zone->zone_dev_attrs[count++] =
+				&constraint_attrs[i].max_time_window_attr.attr;
+		if (pconst->ops->get_min_time_window_us)
+			power_zone->zone_dev_attrs[count++] =
+				&constraint_attrs[i].min_time_window_attr.attr;
+	}
+	power_zone->zone_attr_count = count;
+
+	return ret;
+}
+
+static bool control_type_valid(void *control_type)
+{
+	struct powercap_control_type *pos = NULL;
+	bool found = false;
+
+	mutex_lock(&powercap_cntrl_list_lock);
+
+	list_for_each_entry(pos, &powercap_cntrl_list, node) {
+		if (pos == control_type) {
+			found = true;
+			break;
+		}
+	}
+	mutex_unlock(&powercap_cntrl_list_lock);
+
+	return found;
+}
+
+static ssize_t name_show(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
+{
+	struct powercap_zone *power_zone = to_powercap_zone(dev);
+
+	return sprintf(buf, "%s\n", power_zone->name);
+}
+
+static DEVICE_ATTR_RO(name);
+
+/* Create zone and attributes in sysfs */
+static void create_power_zone_common_attributes(
+					struct powercap_zone *power_zone)
+{
+	int count = 0;
+
+	power_zone->zone_dev_attrs[count++] = &dev_attr_name.attr;
+	if (power_zone->ops->get_max_energy_range_uj)
+		power_zone->zone_dev_attrs[count++] =
+					&dev_attr_max_energy_range_uj.attr;
+	if (power_zone->ops->get_energy_uj)
+		power_zone->zone_dev_attrs[count++] =
+					&dev_attr_energy_uj.attr;
+	if (power_zone->ops->get_power_uw)
+		power_zone->zone_dev_attrs[count++] =
+					&dev_attr_power_uw.attr;
+	if (power_zone->ops->get_max_power_range_uw)
+		power_zone->zone_dev_attrs[count++] =
+					&dev_attr_max_power_range_uw.attr;
+	power_zone->zone_dev_attrs[count] = NULL;
+	power_zone->zone_attr_count = count;
+}
+
+static void powercap_release(struct device *dev)
+{
+	bool allocated;
+
+	if (dev->parent) {
+		struct powercap_zone *power_zone = to_powercap_zone(dev);
+
+		/* Store flag as the release() may free memory */
+		allocated = power_zone->allocated;
+		/* Remove id from parent idr struct */
+		idr_remove(power_zone->parent_idr, power_zone->id);
+		/* Destroy idrs allocated for this zone */
+		idr_destroy(&power_zone->idr);
+		kfree(power_zone->name);
+		kfree(power_zone->zone_dev_attrs);
+		kfree(power_zone->constraints);
+		if (power_zone->ops->release)
+			power_zone->ops->release(power_zone);
+		if (allocated)
+			kfree(power_zone);
+	} else {
+		struct powercap_control_type *control_type =
+						to_powercap_control_type(dev);
+
+		/* Store flag as the release() may free memory */
+		allocated = control_type->allocated;
+		idr_destroy(&control_type->idr);
+		mutex_destroy(&control_type->lock);
+		if (control_type->ops && control_type->ops->release)
+			control_type->ops->release(control_type);
+		if (allocated)
+			kfree(control_type);
+	}
+}
+
+static ssize_t enabled_show(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
+{
+	bool mode = true;
+
+	/* Default is enabled */
+	if (dev->parent) {
+		struct powercap_zone *power_zone = to_powercap_zone(dev);
+		if (power_zone->ops->get_enable)
+			if (power_zone->ops->get_enable(power_zone, &mode))
+				mode = false;
+	} else {
+		struct powercap_control_type *control_type =
+						to_powercap_control_type(dev);
+		if (control_type->ops && control_type->ops->get_enable)
+			if (control_type->ops->get_enable(control_type, &mode))
+				mode = false;
+	}
+
+	return sprintf(buf, "%d\n", mode);
+}
+
+static ssize_t enabled_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf,  size_t len)
+{
+	bool mode;
+
+	if (strtobool(buf, &mode))
+		return -EINVAL;
+	if (dev->parent) {
+		struct powercap_zone *power_zone = to_powercap_zone(dev);
+		if (power_zone->ops->set_enable)
+			if (!power_zone->ops->set_enable(power_zone, mode))
+				return len;
+	} else {
+		struct powercap_control_type *control_type =
+						to_powercap_control_type(dev);
+		if (control_type->ops && control_type->ops->set_enable)
+			if (!control_type->ops->set_enable(control_type, mode))
+				return len;
+	}
+
+	return -ENOSYS;
+}
+
+static struct device_attribute powercap_def_attrs[] = {
+		__ATTR(enabled, S_IWUSR | S_IRUGO, enabled_show,
+							enabled_store),
+		__ATTR_NULL
+};
+
+static struct class powercap_class = {
+	.name = "powercap",
+	.dev_release = powercap_release,
+	.dev_attrs = powercap_def_attrs,
+};
+
+struct powercap_zone *powercap_register_zone(
+				struct powercap_zone *power_zone,
+				struct powercap_control_type *control_type,
+				const char *name,
+				struct powercap_zone *parent,
+				const struct powercap_zone_ops *ops,
+				int nr_constraints,
+				struct powercap_zone_constraint_ops *const_ops)
+{
+	int result;
+	int nr_attrs;
+
+	if (!name || !control_type || !ops ||
+			nr_constraints > MAX_CONSTRAINTS_PER_ZONE ||
+			(!ops->get_energy_uj && !ops->get_power_uw) ||
+			!control_type_valid(control_type))
+		return ERR_PTR(-EINVAL);
+
+	if (power_zone) {
+		if (!ops->release)
+			return ERR_PTR(-EINVAL);
+		memset(power_zone, 0, sizeof(*power_zone));
+	} else {
+		power_zone = kzalloc(sizeof(*power_zone), GFP_KERNEL);
+		if (!power_zone)
+			return ERR_PTR(-ENOMEM);
+		power_zone->allocated = true;
+	}
+	power_zone->ops = ops;
+	power_zone->control_type_inst = control_type;
+	if (!parent) {
+		power_zone->dev.parent = &control_type->dev;
+		power_zone->parent_idr = &control_type->idr;
+	} else {
+		power_zone->dev.parent = &parent->dev;
+		power_zone->parent_idr = &parent->idr;
+	}
+	power_zone->dev.class = &powercap_class;
+
+	mutex_lock(&control_type->lock);
+	/* Using idr to get the unique id */
+	result = idr_alloc(power_zone->parent_idr, NULL, 0, 0, GFP_KERNEL);
+	if (result < 0)
+		goto err_idr_alloc;
+
+	power_zone->id = result;
+	idr_init(&power_zone->idr);
+	power_zone->name = kstrdup(name, GFP_KERNEL);
+	if (!power_zone->name)
+		goto err_name_alloc;
+	dev_set_name(&power_zone->dev, "%s:%x",
+					dev_name(power_zone->dev.parent),
+					power_zone->id);
+	power_zone->constraints = kzalloc(sizeof(*power_zone->constraints) *
+					 nr_constraints, GFP_KERNEL);
+	if (!power_zone->constraints)
+		goto err_const_alloc;
+
+	nr_attrs = nr_constraints * POWERCAP_CONSTRAINTS_ATTRS +
+						POWERCAP_ZONE_MAX_ATTRS + 1;
+	power_zone->zone_dev_attrs = kzalloc(sizeof(void *) *
+						nr_attrs, GFP_KERNEL);
+	if (!power_zone->zone_dev_attrs)
+		goto err_attr_alloc;
+	create_power_zone_common_attributes(power_zone);
+	result = create_constraints(power_zone, nr_constraints, const_ops);
+	if (result)
+		goto err_dev_ret;
+
+	power_zone->zone_dev_attrs[power_zone->zone_attr_count] = NULL;
+	power_zone->dev_zone_attr_group.attrs = power_zone->zone_dev_attrs;
+	power_zone->dev_attr_groups[0] = &power_zone->dev_zone_attr_group;
+	power_zone->dev_attr_groups[1] = NULL;
+	power_zone->dev.groups = power_zone->dev_attr_groups;
+	result = device_register(&power_zone->dev);
+	if (result)
+		goto err_dev_ret;
+
+	control_type->nr_zones++;
+	mutex_unlock(&control_type->lock);
+
+	return power_zone;
+
+err_dev_ret:
+	kfree(power_zone->zone_dev_attrs);
+err_attr_alloc:
+	kfree(power_zone->constraints);
+err_const_alloc:
+	kfree(power_zone->name);
+err_name_alloc:
+	idr_remove(power_zone->parent_idr, power_zone->id);
+err_idr_alloc:
+	if (power_zone->allocated)
+		kfree(power_zone);
+	mutex_unlock(&control_type->lock);
+
+	return ERR_PTR(result);
+}
+EXPORT_SYMBOL_GPL(powercap_register_zone);
+
+int powercap_unregister_zone(struct powercap_control_type *control_type,
+				struct powercap_zone *power_zone)
+{
+	if (!power_zone || !control_type)
+		return -EINVAL;
+
+	mutex_lock(&control_type->lock);
+	control_type->nr_zones--;
+	mutex_unlock(&control_type->lock);
+
+	device_unregister(&power_zone->dev);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(powercap_unregister_zone);
+
+struct powercap_control_type *powercap_register_control_type(
+				struct powercap_control_type *control_type,
+				const char *name,
+				const struct powercap_control_type_ops *ops)
+{
+	int result;
+
+	if (!name)
+		return ERR_PTR(-EINVAL);
+	if (control_type) {
+		if (!ops || !ops->release)
+			return ERR_PTR(-EINVAL);
+		memset(control_type, 0, sizeof(*control_type));
+	} else {
+		control_type = kzalloc(sizeof(*control_type), GFP_KERNEL);
+		if (!control_type)
+			return ERR_PTR(-ENOMEM);
+		control_type->allocated = true;
+	}
+	mutex_init(&control_type->lock);
+	control_type->ops = ops;
+	INIT_LIST_HEAD(&control_type->node);
+	control_type->dev.class = &powercap_class;
+	dev_set_name(&control_type->dev, name);
+	result = device_register(&control_type->dev);
+	if (result) {
+		if (control_type->allocated)
+			kfree(control_type);
+		return ERR_PTR(result);
+	}
+	idr_init(&control_type->idr);
+
+	mutex_lock(&powercap_cntrl_list_lock);
+	list_add_tail(&control_type->node, &powercap_cntrl_list);
+	mutex_unlock(&powercap_cntrl_list_lock);
+
+	return control_type;
+}
+EXPORT_SYMBOL_GPL(powercap_register_control_type);
+
+int powercap_unregister_control_type(struct powercap_control_type *control_type)
+{
+	struct powercap_control_type *pos = NULL;
+
+	if (control_type->nr_zones) {
+		dev_err(&control_type->dev, "Zones of this type still not freed\n");
+		return -EINVAL;
+	}
+	mutex_lock(&powercap_cntrl_list_lock);
+	list_for_each_entry(pos, &powercap_cntrl_list, node) {
+		if (pos == control_type) {
+			list_del(&control_type->node);
+			mutex_unlock(&powercap_cntrl_list_lock);
+			device_unregister(&control_type->dev);
+			return 0;
+		}
+	}
+	mutex_unlock(&powercap_cntrl_list_lock);
+
+	return -ENODEV;
+}
+EXPORT_SYMBOL_GPL(powercap_unregister_control_type);
+
+static int __init powercap_init(void)
+{
+	int result = 0;
+
+	result = seed_constraint_attributes();
+	if (result)
+		return result;
+
+	result = class_register(&powercap_class);
+
+	return result;
+}
+
+device_initcall(powercap_init);
+
+MODULE_DESCRIPTION("PowerCap sysfs Driver");
+MODULE_AUTHOR("Srinivas Pandruvada <[e-mail]>");
+MODULE_LICENSE("GPL v2");

include/linux/powercap.h

···
+/*
+ * powercap.h: Data types and headers for sysfs power capping interface
+ * Copyright (c) 2013, Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc.
+ *
+ */
+
+#ifndef __POWERCAP_H__
+#define __POWERCAP_H__
+
+#include <linux/device.h>
+#include <linux/idr.h>
+
+/*
+ * A power cap class device can contain multiple powercap control_types.
+ * Each control_type can have multiple power zones, which can be independently
+ * controlled. Each power zone can have one or more constraints.
+ */
+
+struct powercap_control_type;
+struct powercap_zone;
+struct powercap_zone_constraint;
+
+/**
+ * struct powercap_control_type_ops - Define control type callbacks
+ * @set_enable:		Enable/Disable whole control type.
+ *			Default is enabled. But this callback allows all zones
+ *			to be in disable state and remove any applied power
+ *			limits. If disabled power zone can only be monitored
+ *			not controlled.
+ * @get_enable:		get Enable/Disable status.
+ * @release:		Callback to inform that last reference to this
+ *			control type is closed. So it is safe to free data
+ *			structure associated with this control type.
+ *			This callback is mandatory if the client own memory
+ *			for the control type.
+ *
+ * This structure defines control type callbacks to be implemented by client
+ * drivers
+ */
+struct powercap_control_type_ops {
+	int (*set_enable) (struct powercap_control_type *, bool mode);
+	int (*get_enable) (struct powercap_control_type *, bool *mode);
+	int (*release) (struct powercap_control_type *);
+};
+
+/**
+ * struct powercap_control_type- Defines a powercap control_type
+ * @name:		name of control_type
+ * @dev:		device for this control_type
+ * @idr:		idr to have unique id for its child
+ * @root_node:		Root holding power zones for this control_type
+ * @ops:		Pointer to callback struct
+ * @node_lock:		mutex for control type
+ * @allocated:		This is possible that client owns the memory
+ *			used by this structure. In this case
+ *			this flag is set to false by framework to
+ *			prevent deallocation during release process.
+ *			Otherwise this flag is set to true.
+ * @ctrl_inst:		link to the control_type list
+ *
+ * Defines powercap control_type. This acts as a container for power
+ * zones, which use same method to control power. E.g. RAPL, RAPL-PCI etc.
+ * All fields are private and should not be used by client drivers.
+ */
+struct powercap_control_type {
+	struct device dev;
+	struct idr idr;
+	int nr_zones;
+	const struct powercap_control_type_ops *ops;
+	struct mutex lock;
+	bool allocated;
+	struct list_head node;
+};
+
+/**
+ * struct powercap_zone_ops - Define power zone callbacks
+ * @get_max_energy_range_uj:	Get maximum range of energy counter in
+ *				micro-joules.
+ * @get_energy_uj:		Get current energy counter in micro-joules.
+ * @reset_energy_uj:		Reset micro-joules energy counter.
+ * @get_max_power_range_uw:	Get maximum range of power counter in
+ *				micro-watts.
+ * @get_power_uw:		Get current power counter in micro-watts.
+ * @set_enable:			Enable/Disable power zone controls.
+ *				Default is enabled.
+ * @get_enable:			get Enable/Disable status.
+ * @release:			Callback to inform that last reference to this
+ *				control type is closed. So it is safe to free
+ *				data structure associated with this
+ *				control type. Mandatory, if client driver owns
+ *				the power_zone memory.
+ *
+ * This structure defines zone callbacks to be implemented by client drivers.
+ * Client drives can define both energy and power related callbacks. But at
+ * the least one type (either power or energy) is mandatory. Client drivers
+ * should handle mutual exclusion, if required in callbacks.
+ */
+struct powercap_zone_ops {
+	int (*get_max_energy_range_uj) (struct powercap_zone *, u64 *);
+	int (*get_energy_uj) (struct powercap_zone *, u64 *);
+	int (*reset_energy_uj) (struct powercap_zone *);
+	int (*get_max_power_range_uw) (struct powercap_zone *, u64 *);
+	int (*get_power_uw) (struct powercap_zone *, u64 *);
+	int (*set_enable) (struct powercap_zone *, bool mode);
+	int (*get_enable) (struct powercap_zone *, bool *mode);
+	int (*release) (struct powercap_zone *);
+};
+
+#define	POWERCAP_ZONE_MAX_ATTRS		6
+#define	POWERCAP_CONSTRAINTS_ATTRS	8
+#define MAX_CONSTRAINTS_PER_ZONE	10
+/**
+ * struct powercap_zone- Defines instance of a power cap zone
+ * @id:			Unique id
+ * @name:		Power zone name.
+ * @control_type_inst:	Control type instance for this zone.
+ * @ops:		Pointer to the zone operation structure.
+ * @dev:		Instance of a device.
+ * @const_id_cnt:	Number of constraint defined.
+ * @idr:		Instance to an idr entry for children zones.
+ * @parent_idr:		To remove reference from the parent idr.
+ * @private_data:	Private data pointer if any for this zone.
+ * @zone_dev_attrs:	Attributes associated with this device.
+ * @zone_attr_count:	Attribute count.
+ * @dev_zone_attr_group: Attribute group for attributes.
+ * @dev_attr_groups:	Attribute group store to register with device.
+ * @allocated:		This is possible that client owns the memory
+ *			used by this structure. In this case
+ *			this flag is set to false by framework to
+ *			prevent deallocation during release process.
+ *			Otherwise this flag is set to true.
+ * @constraint_ptr:	List of constraints for this zone.
+ *
+ * This defines a power zone instance. The fields of this structure are
+ * private, and should not be used by client drivers.
+ */
+struct powercap_zone {
+	int id;
+	char *name;
+	void *control_type_inst;
+	const struct powercap_zone_ops *ops;
+	struct device dev;
+	int const_id_cnt;
+	struct idr idr;
+	struct idr *parent_idr;
+	void *private_data;
+	struct attribute **zone_dev_attrs;
+	int zone_attr_count;
+	struct attribute_group dev_zone_attr_group;
+	const struct attribute_group *dev_attr_groups[2]; /* 1 group + NULL */
+	bool allocated;
+	struct powercap_zone_constraint *constraints;
+};
+
+/**
+ * struct powercap_zone_constraint_ops - Define constraint callbacks
+ * @set_power_limit_uw:		Set power limit in micro-watts.
+ * @get_power_limit_uw:		Get power limit in micro-watts.
+ * @set_time_window_us:		Set time window in micro-seconds.
+ * @get_time_window_us:		Get time window in micro-seconds.
+ * @get_max_power_uw:		Get max power allowed in micro-watts.
+ * @get_min_power_uw:		Get min power allowed in micro-watts.
+ * @get_max_time_window_us:	Get max time window allowed in micro-seconds.
+ * @get_min_time_window_us:	Get min time window allowed in micro-seconds.
+ * @get_name:			Get the name of constraint
+ *
+ * This structure is used to define the constraint callbacks for the client
+ * drivers. The following callbacks are mandatory and can't be NULL:
+ *  set_power_limit_uw
+ *  get_power_limit_uw
+ *  set_time_window_us
+ *  get_time_window_us
+ *  get_name
+ *  Client drivers should handle mutual exclusion, if required in callbacks.
+ */
+struct powercap_zone_constraint_ops {
+	int (*set_power_limit_uw) (struct powercap_zone *, int, u64);
+	int (*get_power_limit_uw) (struct powercap_zone *, int, u64 *);
+	int (*set_time_window_us) (struct powercap_zone *, int, u64);
+	int (*get_time_window_us) (struct powercap_zone *, int, u64 *);
+	int (*get_max_power_uw) (struct powercap_zone *, int, u64 *);
+	int (*get_min_power_uw) (struct powercap_zone *, int, u64 *);
+	int (*get_max_time_window_us) (struct powercap_zone *, int, u64 *);
+	int (*get_min_time_window_us) (struct powercap_zone *, int, u64 *);
+	const char *(*get_name) (struct powercap_zone *, int);
+};
+
+/**
+ * struct powercap_zone_constraint- Defines instance of a constraint
+ * @id:			Instance Id of this constraint.
+ * @power_zone:		Pointer to the power zone for this constraint.
+ * @ops:		Pointer to the constraint callbacks.
+ *
+ * This defines a constraint instance.
+ */
+struct powercap_zone_constraint {
+	int id;
+	struct powercap_zone *power_zone;
+	struct powercap_zone_constraint_ops *ops;
+};
+
+
+/* For clients to get their device pointer, may be used for dev_dbgs */
+#define POWERCAP_GET_DEV(power_zone)	(&power_zone->dev)
+
+/**
+* powercap_set_zone_data() - Set private data for a zone
+* @power_zone:	A pointer to the valid zone instance.
+* @pdata:	A pointer to the user private data.
+*
+* Allows client drivers to associate some private data to zone instance.
+*/
+static inline void powercap_set_zone_data(struct powercap_zone *power_zone,
+						void *pdata)
+{
+	if (power_zone)
+		power_zone->private_data = pdata;
+}
+
+/**
+* powercap_get_zone_data() - Get private data for a zone
+* @power_zone:	A pointer to the valid zone instance.
+*
+* Allows client drivers to get private data associate with a zone,
+* using call to powercap_set_zone_data.
+*/
+static inline void *powercap_get_zone_data(struct powercap_zone *power_zone)
+{
+	if (power_zone)
+		return power_zone->private_data;
+	return NULL;
+}
+
+/**
+* powercap_register_control_type() - Register a control_type with framework
+* @control_type:	Pointer to client allocated memory for the control type
+*			structure storage. If this is NULL, powercap framework
+*			will allocate memory and own it.
+*			Advantage of this parameter is that client can embed
+*			this data in its data structures and allocate in a
+*			single call, preventing multiple allocations.
+* @control_type_name:	The Name of this control_type, which will be shown
+*			in the sysfs Interface.
+* @ops:			Callbacks for control type. This parameter is optional.
+*
+* Used to create a control_type with the power capping class. Here control_type
+* can represent a type of technology, which can control a range of power zones.
+* For example a control_type can be RAPL (Running Average Power Limit)
+* Intel® 64 and IA-32 Processor Architectures. The name can be any string
+* which must be unique, otherwise this function returns NULL.
+* A pointer to the control_type instance is returned on success.
+*/
+struct powercap_control_type *powercap_register_control_type(
+				struct powercap_control_type *control_type,
+				const char *name,
+				const struct powercap_control_type_ops *ops);
+
+/**
+* powercap_unregister_control_type() - Unregister a control_type from framework
+* @instance:	A pointer to the valid control_type instance.
+*
+* Used to unregister a control_type with the power capping class.
+* All power zones registered under this control type have to be unregistered
+* before calling this function, or it will fail with an error code.
+*/
+int powercap_unregister_control_type(struct powercap_control_type *instance);
+
+/* Zone register/unregister API */
+
+/**
+* powercap_register_zone() - Register a power zone
+* @power_zone:	Pointer to client allocated memory for the power zone structure
+*		storage. If this is NULL, powercap framework will allocate
+*		memory and own it. Advantage of this parameter is that client
+*		can embed this data in its data structures and allocate in a
+*		single call, preventing multiple allocations.
+* @control_type: A control_type instance under which this zone operates.
+* @name:	A name for this zone.
+* @parent:	A pointer to the parent power zone instance if any or NULL
+* @ops:		Pointer to zone operation callback structure.
+* @no_constraints: Number of constraints for this zone
+* @const_ops:	Pointer to constraint callback structure
+*
+* Register a power zone under a given control type. A power zone must register
+* a pointer to a structure representing zone callbacks.
+* A power zone can be located under a parent power zone, in which case @parent
+* should point to it.  Otherwise, if @parent is NULL, the new power zone will
+* be located directly under the given control type
+* For each power zone there may be a number of constraints that appear in the
+* sysfs under that zone as attributes with unique numeric IDs.
+* Returns pointer to the power_zone on success.
+*/
+struct powercap_zone *powercap_register_zone(
+			struct powercap_zone *power_zone,
+			struct powercap_control_type *control_type,
+			const char *name,
+			struct powercap_zone *parent,
+			const struct powercap_zone_ops *ops,
+			int nr_constraints,
+			struct powercap_zone_constraint_ops *const_ops);
+
+/**
+* powercap_unregister_zone() - Unregister a zone device
+* @control_type:	A pointer to the valid instance of a control_type.
+* @power_zone:	A pointer to the valid zone instance for a control_type
+*
+* Used to unregister a zone device for a control_type.  Caller should
+* make sure that children for this zone are unregistered first.
+*/
+int powercap_unregister_zone(struct powercap_control_type *control_type,
+				struct powercap_zone *power_zone);
+
+#endif