[PATCH 1/4] ACPI / PM: Expose power states of ACPI devices to user space

Rafael J. Wysocki
2013-01-22T02:22:55Z

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

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: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
Documentation/ABI/testing/sysfs-devices-power_state | 20 ++++++
Documentation/ABI/testing/sysfs-devices-real_power_state | 23 +++++++
drivers/acpi/scan.c | 49 ++++++++++++++-
3 files changed, 91 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/acpi/scan.c
===================================================================
--- linux-pm.orig/drivers/acpi/scan.c
+++ linux-pm/drivers/acpi/scan.c
@@ -178,6 +178,32 @@ err_out:
}
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(struc
* 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(str
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
*/
Index: linux-pm/Documentation/ABI/testing/sysfs-devices-power_state
===================================================================
--- /dev/null
+++ linux-pm/Documentation/ABI/testing/sysfs-devices-power_state
@@ -0,0 +1,20 @@
+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.
Index: linux-pm/Documentation/ABI/testing/sysfs-devices-real_power_state
===================================================================
--- /dev/null
+++ linux-pm/Documentation/ABI/testing/sysfs-devices-real_power_state
@@ -0,0 +1,23 @@
+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.