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authorZhang Rui <rui.zhang@intel.com>2008-12-12 00:24:52 +0300
committerLen Brown <len.brown@intel.com>2008-12-12 00:24:52 +0300
commit935e5f290ec1eb0f1c15004421f5fd3154380fd5 (patch)
tree2f116b2de376df6621ab700246a96e25a1183b84 /drivers/acpi/video.c
parent6c34bc2976b30dc8b56392c020e25bae1f363cab (diff)
downloadlinux-935e5f290ec1eb0f1c15004421f5fd3154380fd5.tar.xz
ACPI: video: Fix reversed brightness behavior on ThinkPad SL series
Section B.6.2 of ACPI 3.0b specification that defines _BCL method doesn't require the brightness levels returned to be sorted. At least ThinkPad SL300 (and probably all IdeaPads) returns the array reversed (i.e. bightest levels have lowest indexes), which causes the brightness management behave in completely reversed manner on these machines (brightness increases when the laptop is idle, while the display dims when used). Sorting the array by brightness level values after reading the list fixes the issue. http://bugzilla.kernel.org/show_bug.cgi?id=12037 Signed-off-by: Zhang Rui <rui.zhang@intel.com> Tested-by: Lubomir Rintel <lkundrak@v3.sk> Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'drivers/acpi/video.c')
-rw-r--r--drivers/acpi/video.c15
1 files changed, 15 insertions, 0 deletions
diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index baa441929720..38bf8b43fd19 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -36,6 +36,7 @@
#include <linux/backlight.h>
#include <linux/thermal.h>
#include <linux/video_output.h>
+#include <linux/sort.h>
#include <asm/uaccess.h>
#include <acpi/acpi_bus.h>
@@ -626,6 +627,16 @@ acpi_video_bus_DOS(struct acpi_video_bus *video, int bios_flag, int lcd_flag)
}
/*
+ * Simple comparison function used to sort backlight levels.
+ */
+
+static int
+acpi_video_cmp_level(const void *a, const void *b)
+{
+ return *(int *)a - *(int *)b;
+}
+
+/*
* Arg:
* device : video output device (LCD, CRT, ..)
*
@@ -676,6 +687,10 @@ acpi_video_init_brightness(struct acpi_video_device *device)
count++;
}
+ /* don't sort the first two brightness levels */
+ sort(&br->levels[2], count - 2, sizeof(br->levels[2]),
+ acpi_video_cmp_level, NULL);
+
if (count < 2)
goto out_free_levels;