ACPI / PM: Expose current status of ACPI power resources

Since ACPI power resources are going to be used more extensively on
new hardware platforms, it becomes necessary for user space (powertop
in particular) to observe some properties of those resources for
diagnostics purposes.

For this reason, expose the current status of each ACPI power
resource to user space via sysfs by adding a new resource_in_use
attribute to the sysfs directory representing the given power
resource.

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

1 files changed, 25 insertions, 1 deletions

diff --git a/drivers/acpi/power.c b/drivers/acpi/power.c
index 3f16dd4..946720a 100644
--- a/drivers/acpi/power.c
+++ b/drivers/acpi/power.c
@@ -87,6 +87,12 @@ static DEFINE_MUTEX(power_resource_list_lock);
                              Power Resource Management
    -------------------------------------------------------------------------- */
 
+static inline
+struct acpi_power_resource *to_power_resource(struct acpi_device *device)
+{
+	return container_of(device, struct acpi_power_resource, device);
+}
+
 static struct acpi_power_resource *acpi_power_get_context(acpi_handle handle)
 {
 	struct acpi_device *device;
@@ -94,7 +100,7 @@ static struct acpi_power_resource *acpi_power_get_context(acpi_handle handle)
 	if (acpi_bus_get_device(handle, &device))
 		return NULL;
 
-	return container_of(device, struct acpi_power_resource, device);
+	return to_power_resource(device);
 }
 
 static int acpi_power_resources_list_add(acpi_handle handle,
@@ -678,6 +684,21 @@ static void acpi_release_power_resource(struct device *dev)
 	kfree(resource);
 }
 
+static ssize_t acpi_power_in_use_show(struct device *dev,
+				      struct device_attribute *attr,
+				      char *buf) {
+	struct acpi_power_resource *resource;
+
+	resource = to_power_resource(to_acpi_device(dev));
+	return sprintf(buf, "%u\n", !!resource->ref_count);
+}
+static DEVICE_ATTR(resource_in_use, 0444, acpi_power_in_use_show, NULL);
+
+static void acpi_power_sysfs_remove(struct acpi_device *device)
+{
+	device_remove_file(&device->dev, &dev_attr_resource_in_use);
+}
+
 int acpi_add_power_resource(acpi_handle handle)
 {
 	struct acpi_power_resource *resource;
@@ -725,6 +746,9 @@ int acpi_add_power_resource(acpi_handle handle)
 	if (result)
 		goto err;
 
+	if (!device_create_file(&device->dev, &dev_attr_resource_in_use))
+		device->remove = acpi_power_sysfs_remove;
+
 	mutex_lock(&power_resource_list_lock);
 	list_add(&resource->list_node, &acpi_power_resource_list);
 	mutex_unlock(&power_resource_list_lock);