On 12/24/2012 06:05 PM, joeyli wrote: > 於 一，2012-12-24 於 16:32 -0500，Ben Jencks 提到： >> The addition of "Windows 2012" to the OSI strings in the 3.7 cycle has >> caused backlight brightness adjustment to break on my ThinkPad T530. >> >> Without "Windows 2012" _BCL returns the actual 16 brightness levels: >> >> 5, 10, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 80, 90, 100 >> >> When "Windows 2012" is present, it returns 101 levels 0-100, but _BCM >> rounds any value up to one of the real values above. >> >> This interacts badly with gnome-settings-daemon, which attempts to >> change brightness in increments of 5 (1/20 of 100). If brightness is >> currently 100, it attempts to decrement it to 95, but it gets rounded >> back up to 100, so it's impossible to decrease the brightness. >> >> Booting with acpi_osi="!Windows 2012" fixes the problem, though I'm >> not >> sure if it introduces others; I see several other things depend on >> WIN8 >> in DSDT. >> >> Perhaps this should be fixed in gnome-settings-daemon, but since it >> appears on the surface to be a kernel regression (3.6 works, 3.7 >> broken) >> I thought I'd report it here first. > > Yes, this is g-s-d's problem, g-s-d should adapt to more levels of > brightness: > > plugins/power/gsd-power-manager.c > > /* on ACPI machines we have 4-16 levels, on others it's ~150 */ > #define BRIGHTNESS_STEP_AMOUNT(max) ((max) < 20 ? 1 : (max) / 20) Actually, thinking about this some more, I'm not sure what g-s-d could do about this. It could behave better if brightness changes don't "stick", but as long as the hardware/kernel is lying to userspace about how many brightness levels are available the experience can't be completely right. If the exact brightness levels aren't exposed, pressing the brightness up/down keys will skip a real level or not change the real level at all in some cases. Would it be possible to add a quirk in to exclude "Windows 2012" on this hardware/bios? -Ben -- 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
