On Sun, Mar 31, 2013 at 06:07:57PM +0800, Aaron Lu wrote: > 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@xxxxxxxxx> schrieb: > >> > >>>On Sun, Mar 31, 2013 at 08:15:14AM +0200, Danny Baumann wrote: > >>>>Artem Savkov <artem.savkov@xxxxxxxxx> 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 > Submitted: https://bugzilla.kernel.org/show_bug.cgi?id=56011 -- Regards, Artem -- 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
