[RFC][Update 2][PATCH 1/4] ACPI / PM: Export power states of ACPI devices via sysfs

Rafael J. Wysocki
2013-01-21T13:03:11Z

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 a new
attribute 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 | 21 ++++++++++++++
drivers/acpi/scan.c | 29 +++++++++++++++++++-
2 files changed, 49 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 +178,23 @@ err_out:
}
EXPORT_SYMBOL(acpi_bus_hot_remove_device);

+static ssize_t 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 %s\n", acpi_power_state_string(state),
+ 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 +386,15 @@ 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)
+ goto end;
+ }
+
+ if (dev->flags.power_manageable)
+ result = device_create_file(&dev->dev, &dev_attr_power_state);
+
end:
return result;
}
@@ -380,6 +404,9 @@ 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 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 +1,21 @@
+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 pair of strings representing the
+ current ACPI power state of the given device node and the ACPI
+ power state the device node would be in if it did not share
+ power resources with other device nodes, respectively. If the
+ given device node does not share power resources with other
+ device nodes or it does not use power resource objects for power
+ management, the strings are always the same.
+
+ For each of the strings the possible values are "D0", "D1",
+ "D2", "D3hot", and "D3cold" which reflect the power state names
+ defined by the ACPI specification (4.0 and above).
+
+ This attribute is read-only.