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 is pick another value, any other value, and br->level[3] works just fine. -- 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
