On 08/02/2013 03:59 PM, Felipe Contreras wrote: > 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 For your system, yes it is unnecessarily complicated. But since this is a quirk, it better solves as many potential problems as possible, or we would simply use a DMI entry to do the quirk. -Aaron > 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) > -- 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
