ACPI, cpuidle: Clarify C-state description in sysfs

Add a new sysfs entry under cpuidle states. desc - can be used by driver to
communicate to userspace any specific information about the state.
This helps in identifying the exact hardware C-states behind the ACPI C-state
definition.

Idea is to export this through powertop, which will help to map the C-state
reported by powertop to actual hardware C-state.

Signed-off-by: Venkatesh Pallipadi <[e-mail]>
Signed-off-by: Len Brown <[e-mail]>

arch/x86/kernel/acpi/cstate.c

···
 		printk(KERN_DEBUG "Monitor-Mwait will be used to enter C-%d "
 		       "state\n", cx->type);
 	}
+	snprintf(cx->desc, ACPI_CX_DESC_LEN, "ACPI FFH INTEL MWAIT 0x%x",
+		 cx->address);
 
 out:
 	set_cpus_allowed(current, saved_mask);

drivers/acpi/processor_idle.c

···
 				 * Otherwise, ignore this info and continue.
 				 */
 				cx.entry_method = ACPI_CSTATE_HALT;
+				snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI HLT");
 			} else {
 				continue;
 			}
+		} else {
+			snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI IOPORT 0x%x",
+				 cx.address);
 		}
+
 
 		obj = &(element->package.elements[2]);
 		if (obj->type != ACPI_TYPE_INTEGER)
···
 		return -EINVAL;
 	}
 
+	for (i = 0; i < CPUIDLE_STATE_MAX; i++) {
+		dev->states[i].name[0] = '\0';
+		dev->states[i].desc[0] = '\0';
+	}
+
 	for (i = 1; i < ACPI_PROCESSOR_MAX_POWER && i <= max_cstate; i++) {
 		cx = &pr->power.states[i];
 		state = &dev->states[count];
···
 		cpuidle_set_statedata(state, cx);
 
 		snprintf(state->name, CPUIDLE_NAME_LEN, "C%d", i);
+		strncpy(state->desc, cx->desc, CPUIDLE_DESC_LEN);
 		state->exit_latency = cx->latency;
 		state->target_residency = cx->latency * latency_factor;
 		state->power_usage = cx->power;

drivers/cpuidle/cpuidle.c

···
 
 	cpuidle_set_statedata(state, NULL);
 
-	snprintf(state->name, CPUIDLE_NAME_LEN, "C0 (poll idle)");
+	snprintf(state->name, CPUIDLE_NAME_LEN, "C0");
+	snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
 	state->exit_latency = 0;
 	state->target_residency = 0;
 	state->power_usage = -1;

drivers/cpuidle/sysfs.c

···
 	return sprintf(buf, "%u\n", state->_name);\
 }
 
-static ssize_t show_state_name(struct cpuidle_state *state, char *buf)
-{
-	return sprintf(buf, "%s\n", state->name);
+#define define_show_state_str_function(_name) \
+static ssize_t show_state_##_name(struct cpuidle_state *state, char *buf) \
+{ \
+	if (state->_name[0] == '\0')\
+		return sprintf(buf, "<null>\n");\
+	return sprintf(buf, "%s\n", state->_name);\
 }
 
 define_show_state_function(exit_latency)
 define_show_state_function(power_usage)
 define_show_state_function(usage)
 define_show_state_function(time)
+define_show_state_str_function(name)
+define_show_state_str_function(desc)
+
 define_one_state_ro(name, show_state_name);
+define_one_state_ro(desc, show_state_desc);
 define_one_state_ro(latency, show_state_exit_latency);
 define_one_state_ro(power, show_state_power_usage);
 define_one_state_ro(usage, show_state_usage);
···
 
 static struct attribute *cpuidle_state_default_attrs[] = {
 	&attr_name.attr,
+	&attr_desc.attr,
 	&attr_latency.attr,
 	&attr_power.attr,
 	&attr_usage.attr,

include/acpi/processor.h

···
 #define DOMAIN_COORD_TYPE_SW_ANY	0xfd
 #define DOMAIN_COORD_TYPE_HW_ALL	0xfe
 
-#define ACPI_CSTATE_SYSTEMIO	(0)
-#define ACPI_CSTATE_FFH		(1)
-#define ACPI_CSTATE_HALT	(2)
+#define ACPI_CSTATE_SYSTEMIO	0
+#define ACPI_CSTATE_FFH		1
+#define ACPI_CSTATE_HALT	2
+
+#define ACPI_CX_DESC_LEN	32
 
 /* Power Management */
 
···
 	u64 time;
 	struct acpi_processor_cx_policy promotion;
 	struct acpi_processor_cx_policy demotion;
+	char desc[ACPI_CX_DESC_LEN];
 };
 
 struct acpi_processor_power {

include/linux/cpuidle.h

···
 
 #define CPUIDLE_STATE_MAX	8
 #define CPUIDLE_NAME_LEN	16
+#define CPUIDLE_DESC_LEN	32
 
 struct cpuidle_device;
 
···
 
 struct cpuidle_state {
 	char		name[CPUIDLE_NAME_LEN];
+	char		desc[CPUIDLE_DESC_LEN];
 	void		*driver_data;
 
 	unsigned int	flags;