ACPI video: introduce module parameter video.use_bios_initial_backlight
Introduce module parameter video.use_bios_initial_backlight.
Some BIOSes claim they use the minimum backlight at boot,
and this may bring dimming screen after boot.
https://bugzilla.kernel.org/show_bug.cgi?id=21212
use video.use_bios_initl_backlight=0 to use
the maximum backlight level after boot.
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 5cd0228..89f19a8 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -81,6 +81,13 @@
static int allow_duplicates;
module_param(allow_duplicates, bool, 0644);
+/*
+ * Some BIOSes claim they use minimum backlight at boot,
+ * and this may bring dimming screen after boot
+ */
+static int use_bios_initial_backlight = 1;
+module_param(use_bios_initial_backlight, bool, 0644);
+
static int register_count = 0;
static int acpi_video_bus_add(struct acpi_device *device);
static int acpi_video_bus_remove(struct acpi_device *device, int type);
@@ -766,9 +773,11 @@
* when invoked for the first time, i.e. level_old is invalid.
* set the backlight to max_level in this case
*/
- for (i = 2; i < br->count; i++)
- if (level_old == br->levels[i])
- level = level_old;
+ if (use_bios_initial_backlight) {
+ for (i = 2; i < br->count; i++)
+ if (level_old == br->levels[i])
+ level = level_old;
+ }
goto set_level;
}