From 936574fd1687ea60a88a5070059e40c7dec7f414 Mon Sep 17 00:00:00 2001 From: Zhang Rui Date: Thu, 11 Dec 2008 16:24:52 -0500 Subject: [PATCH] ACPI: video: Fix reversed brightness behavior on ThinkPad SL series commit 935e5f290ec1eb0f1c15004421f5fd3154380fd5 upstream. 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 Tested-by: Lubomir Rintel Signed-off-by: Len Brown Signed-off-by: Thomas Renninger Signed-off-by: Greg Kroah-Hartman --- drivers/acpi/video.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c index 9bf8f86f536d..8bcca4b29bb9 100644 --- a/drivers/acpi/video.c +++ b/drivers/acpi/video.c @@ -36,6 +36,7 @@ #include #include #include +#include #include #include @@ -630,6 +631,16 @@ acpi_video_bus_DOS(struct acpi_video_bus *video, int bios_flag, int lcd_flag) return status; } +/* + * 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, ..) @@ -681,6 +692,10 @@ 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; -- 2.39.5