UBUNTU: SAUCE (no-up) Provide a param for allowing the BIOS to handle changing the brightness on AC/battery status changes.

BugLink: http://bugs.launchpad.net/bugs/949311

We currently carry a SAUCE patch which lets the OS handle the brightness
levels automatically when connecting/disconnecting AC. There are some
laptops (MSI Wind) for which this doesn't work. Provide a driver param
which allows this behaviour to be overriden.

Signed-off-by: Brad Figg <brad.figg@canonical.com>
Acked-by: Colin King <colin.king@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 450a611b5fc..4c73f9433ec 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -74,6 +74,14 @@ static int brightness_switch_enabled = 1;
 module_param(brightness_switch_enabled, bool, 0644);
 
 /*
+ *  The Default is to let the OS handle brightness autoswitching due to
+ *  AC/battery status changes. On some laptops (MSI Wind) this doesn't
+ *  work so we need a workaround.
+ */
+static int brightness_autoswitch_via_bios = 0;
+module_param(brightness_autoswitch_via_bios, bool, 0644);
+
+/*
  * By default, we don't allow duplicate ACPI video bus devices
  * under the same VGA controller
  */
@@ -1422,7 +1430,7 @@ static int acpi_video_bus_put_devices(struct acpi_video_bus *video)
 
 static int acpi_video_bus_start_devices(struct acpi_video_bus *video)
 {
-        return acpi_video_bus_DOS(video, 0, 1);
+        return acpi_video_bus_DOS(video, 0, !brightness_autoswitch_via_bios);
 }
 
 static int acpi_video_bus_stop_devices(struct acpi_video_bus *video)