ACPI: video: reset brightness on resume

Some machines seem to need the backlight brightness to be reset on resume.
Add support for doing so to the video module.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/video.c

@@ -77,6 +77,7 @@ module_param(brightness_switch_enabled, bool, 0644);
 
 static int acpi_video_bus_add(struct acpi_device *device);
 static int acpi_video_bus_remove(struct acpi_device *device, int type);
+static int acpi_video_resume(struct acpi_device *device);
 
 static const struct acpi_device_id video_device_ids[] = {
 	{ACPI_VIDEO_HID, 0},
@@ -91,6 +92,7 @@ static struct acpi_driver acpi_video_bus = {
 	.ops = {
 		.add = acpi_video_bus_add,
 		.remove = acpi_video_bus_remove,
+		.resume = acpi_video_resume,
 		},
 };
 
@@ -1837,6 +1839,25 @@ static void acpi_video_device_notify(acpi_handle handle, u32 event, void *data)
 }
 
 static int instance;
+static int acpi_video_resume(struct acpi_device *device)
+{
+	struct acpi_video_bus *video;
+	struct acpi_video_device *video_device;
+	int i;
+
+	if (!device || !acpi_driver_data(device))
+		return -EINVAL;
+
+	video = acpi_driver_data(device);
+
+	for (i = 0; i < video->attached_count; i++) {
+		video_device = video->attached_array[i].bind_info;
+		if (video_device && video_device->backlight)
+			acpi_video_set_brightness(video_device->backlight);
+	}
+	return AE_OK;
+}
+
 static int acpi_video_bus_add(struct acpi_device *device)
 {
 	acpi_status status;