On 08/02/2013 04:14 PM, Felipe Contreras wrote: > On Fri, Aug 2, 2013 at 3:06 AM, Aaron Lu <aaron.lu@xxxxxxxxx> wrote: >> 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. > > The only difference between my patch and yours is that your patch > checks that br->level[i] is not the current level, but that check is > not necessary. If _BQC always returns the max level, all we need to do _BQC does not always returns the max level. > is pick another value, any other value, and br->level[3] works just > fine. For a _BCL only having 4 elements { 100, 40, 40, 100 }, the br->levels[3] will be the max level. The example here may be too crazy to be true, but since we are dealing with firmware, I tend to believe anything could happen. -Aaron -- 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
