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: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 48 insertions, 1 deletions

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 8b3b18846c8c..9761d589f3f5 100644
--- a/drivers/acpi/scan.c
+++ b/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(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
          */