Messages in this thread | | | Date | Sun, 31 Mar 2013 18:07:57 +0800 | From | Aaron Lu <> | Subject | Re: [PATCH] acpi/video: lcd_get_level_current doen't return current level |
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On 03/31/2013 04:16 PM, Artem Savkov wrote: > On Sun, Mar 31, 2013 at 09:04:21AM +0200, Danny Baumann wrote: >> Hi, >> >> Artem Savkov <artem.savkov@gmail.com> schrieb: >> >>> On Sun, Mar 31, 2013 at 08:15:14AM +0200, Danny Baumann wrote: >>>> Artem Savkov <artem.savkov@gmail.com> schrieb: >>>>> acpi_video_device_lcd_get_level_current() called >>>>> acpi_video_bqc_value_to_level() >>>>> with "*level" as a second argument, resulting in level being >>> returned >>>>> based on >>>>> initial input, not current brightness, breaking backlight controls. >>>> I don't think this change is correct. As level was passed as >>> parameter into the evaluation of _BQC, *level contains the AML returned >>> brightness level afterwards, so it's correct to use it as an input to >>> acpi_video_bqc_value_to_level(). Actually, the whole point of >>> acpi_video_device_lcd_get_level_current() is to update >>> device->brightness->curr, so it doesn't make sense to me to use it in >>> that function. >>>> >>>> What's the exact problem this patch tries to solve? >>> >>> I'm running a -next kernel on my laptop and couple of days ago keyboard >>> backlight controls stopped working: only 2 lower brightness levels. >>> I've >>> debugged it a bit and found out that acpi_video_switch_brightness() >>> calls >>> acpi_video_device_lcd_get_level_current() with level uninitialized and >>> always gets lowest posible value. >> >> The point is: after the acpi_evaluate_object call, *level must contain the current brightness level, otherwise your BIOS is broken (this happens: e.g. my laptop always returns 100 from _BQC in Windows 8 mode). You can verify this easily by initializing level_current to some invalid value and checking it again after the call to _get_level_current. I'd be pretty surprised if the value didn't change. Also, if you look at [1], you'll see that the code operated on *level before as well. >> This problem may have been obscured by the fact that the brightness device wasn't initialized properly before my patches went in. Does acpi_video_switch_brightness actually do anything for you when reverting the 3 newest commits of video.c? > > Yes, you are right. Both my patch and the version before your patches > result in initial acpi_video_device_lcd_get_level_current call ending > with invalid level being returned and bqc disabled, so they both just > use *level = brightness->curr after that. >
OK, this suggests the _BQC control method of your system is broken. Please kindly file a bug in bugzilla.kernel.org, against ACPI/Power-Video and attach the output of acpidump and dmidecode there, I want to take a look, thanks.
-Aaron
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