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? Regards, Danny [1] https://git.kernel.org/cgit/linux/kernel/git/rafael/linux-pm.git/commit/drivers/acpi/video.c?h=linux-next&id=994fa63c5b126df6e9f31ef4e09000e2e243234b -- 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
