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Commit 836aedb1 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
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ACPI / PM: Expose power states of ACPI devices to user space 



Make it possible to retrieve the current power state of a device with
ACPI power management from user space via sysfs by adding two new
attributes, power_state and real_power_state, to the sysfs directory
associated with the struct acpi_device object representing the
device's ACPI node.

Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent cf860be6

Documentation/ABI/testing/sysfs-devices-power_state

0 → 100644
+20 −0
Original line number Diff line number Diff line 
What:		/sys/devices/.../power_state

Date:		January 2013

Contact:	Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Description:

		The /sys/devices/.../power_state attribute is only present for

		device objects representing ACPI device nodes that provide power

		management methods.



		If present, it contains a string representing the current ACPI

		power state of the given device node.  Its possible values,

		"D0", "D1", "D2", "D3hot", and "D3cold", reflect the power state

		names defined by the ACPI specification (ACPI 4 and above).



		If the device node uses shared ACPI power resources, this state

		determines a list of power resources required not to be turned

		off.  However, some power resources needed by the device node in

		higher-power (lower-number) states may also be ON because of

		some other devices using them at the moment.



		This attribute is read-only.

Documentation/ABI/testing/sysfs-devices-real_power_state

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+23 −0
Original line number Diff line number Diff line 
What:		/sys/devices/.../real_power_state

Date:		January 2013

Contact:	Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Description:

		The /sys/devices/.../real_power_state attribute is only present

		for device objects representing ACPI device nodes that provide

		power management methods and use ACPI power resources for power

		management.



		If present, it contains a string representing the real ACPI

		power state of the given device node as returned by the _PSC

		control method or inferred from the configuration of power

		resources.  Its possible values, "D0", "D1", "D2", "D3hot", and

		"D3cold", reflect the power state names defined by the ACPI

		specification (ACPI 4 and above).



		In some situations the value of this attribute may be different

		from the value of the /sys/devices/.../power_state attribute for

		the same device object.  If that happens, some shared power

		resources used by the device node are only ON because of some

		other devices using them at the moment.



		This attribute is read-only.

drivers/acpi/scan.c

+48 −1
Original line number Diff line number Diff line
@@ -178,6 +178,32 @@ void acpi_bus_hot_remove_device(void *context) 
}

EXPORT_SYMBOL(acpi_bus_hot_remove_device);



static ssize_t real_power_state_show(struct device *dev,

				     struct device_attribute *attr, char *buf)

{

	struct acpi_device *adev = to_acpi_device(dev);

	int state;

	int ret;



	ret = acpi_device_get_power(adev, &state);

	if (ret)

		return ret;



	return sprintf(buf, "%s\n", acpi_power_state_string(state));

}



static DEVICE_ATTR(real_power_state, 0444, real_power_state_show, NULL);



static ssize_t power_state_show(struct device *dev,

				struct device_attribute *attr, char *buf)

{

	struct acpi_device *adev = to_acpi_device(dev);



	return sprintf(buf, "%s\n", acpi_power_state_string(adev->power.state));

}



static DEVICE_ATTR(power_state, 0444, power_state_show, NULL);



static ssize_t

acpi_eject_store(struct device *d, struct device_attribute *attr,

		const char *buf, size_t count)
@@ -369,8 +395,22 @@ static int acpi_device_setup_files(struct acpi_device *dev) 
         * hot-removal function from userland.

         */

	status = acpi_get_handle(dev->handle, "_EJ0", &temp);

	if (ACPI_SUCCESS(status))

	if (ACPI_SUCCESS(status)) {

		result = device_create_file(&dev->dev, &dev_attr_eject);

		if (result)

			return result;

	}



	if (dev->flags.power_manageable) {

		result = device_create_file(&dev->dev, &dev_attr_power_state);

		if (result)

			return result;



		if (dev->power.flags.power_resources)

			result = device_create_file(&dev->dev,

						    &dev_attr_real_power_state);

	}



end:

	return result;

}
@@ -380,6 +420,13 @@ static void acpi_device_remove_files(struct acpi_device *dev) 
	acpi_status status;

	acpi_handle temp;



	if (dev->flags.power_manageable) {

		device_remove_file(&dev->dev, &dev_attr_power_state);

		if (dev->power.flags.power_resources)

			device_remove_file(&dev->dev,

					   &dev_attr_real_power_state);

	}



	/*

	 * If device has _STR, remove 'description' file

	 */