On Thu, Aug 1, 2013 at 11:59 PM, Aaron Lu <aaron.lu@xxxxxxxxx> wrote: > On 08/02/2013 12:50 PM, Felipe Contreras wrote: >> On Thu, Aug 1, 2013 at 11:30 PM, Aaron Lu <aaron.lu@xxxxxxxxx> wrote: >>> Please see acpi_video_bqc_quirk, we set _BQC_use_index by revert the >>> level on a reversed _BCL, so we will need to revert level here too. >> >> I cannot parse that sentence, but nothing needs to change there; to >> find out if _BQC is using an index, we need to see if the returned >> value is the index of the level we are looking for, and to find that >> out we need the original list of levels, which can be found by >> reverting the already reverted list. If this wasn't the case there > > Yes, but instead of reverting the already reverted list, we revert the > returned value to get the correct index in the reverted list. But your > patch removes the revert, is it correct? It removes the revert in acpi_video_bqc_value_to_level(), not acpi_video_bqc_quirk(). If I remove both reverts it doesn't work on this machine, however, I think it works by accident. 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. -- 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
