On Fri, Aug 2, 2013 at 1:56 AM, Aaron Lu <aaron.lu@xxxxxxxxx> wrote: > On 08/02/2013 02:44 PM, Felipe Contreras wrote: >> The initial _BCM commands don't work, so the level remains at 100%. >> Since the level is max_level, acpi_video_bqc_quirk() tries with the >> first level, which is 0, and 0 happens to be the index of 100. >> >> So _BQC is returning 100, which is not the index of 0 (what we tested >> for), but actually 100. >> >> I think the current code is correct, but acpi_video_bqc_quirk() should >> be testing br->levels[3], or anything other than 0/100 which can be >> easily confused. >> >> If so, the code would find that _BQC doesn't work on this machine (in >> win8 mode)... at least initially. My guess is that it only starts to >> work after acpi_video_bus_start_devices() is called. >> >> Forcing br->flags._BQC_use_index = 0 seems to work. > > Seems ASUS machines tend to have this issue: > https://bugzilla.kernel.org/show_bug.cgi?id=52951 > https://bugzilla.kernel.org/show_bug.cgi?id=56711 I don't see any real solution for the ACPI driver. > I have a patch to enhance the quirk some time ago: > https://github.com/aaronlu/linux/commit/0a3d2c5b59caf80ae5bb1ca1fda0f7bf448b38c9 I think this is unnecessarily complicated; the comment makes it clear that the purpose is to find out if _BQC is working, and this does the trick: >From 2bfa401b0a50fcde292ac0eb60cb6f857caf2fc6 Mon Sep 17 00:00:00 2001 From: Felipe Contreras <felipe.contreras@xxxxxxxxx> Date: Fri, 2 Aug 2013 02:27:44 -0500 Subject: [PATCH] acpi: video: improve quirk check If the _BCL package is descending, the first level (br->levels[2]) will be 0, and if the number of levels matches the number of steps, we might confuse a returned level to mean the index. For example: current_level = max_level = 100 test_level = 0 returned level = 100 In this case 100 means the level, not the index, and _BCM failed. But if the _BCL package is descending, the index of level 0 is also 100, so we assume _BQC is indexed, when it's not. The solution is simple; test anything other than the first level (e.g. 1). Signed-off-by: Felipe Contreras <felipe.contreras@xxxxxxxxx> --- drivers/acpi/video.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c index 0ec434d..e1284b8 100644 --- a/drivers/acpi/video.c +++ b/drivers/acpi/video.c @@ -689,7 +689,7 @@ static int acpi_video_bqc_quirk(struct acpi_video_device *device, * Some systems always report current brightness level as maximum * through _BQC, we need to test another value for them. */ - test_level = current_level == max_level ? br->levels[2] : max_level; + test_level = current_level == max_level ? br->levels[3] : max_level; result = acpi_video_device_lcd_set_level(device, test_level); if (result) -- 1.8.3.4 -- Felipe Contreras -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
