On Thu, Jul 31, 2014 at 10:05:14PM +0100, John Marsden wrote: > On 31 July 2014 09:09, Aaron Lu <aaron.lu@xxxxxxxxx> wrote: > > Please add acpi_backlight=vendor to kernel cmdline and see if that makes > > the backlight work. What it does is to tell ACPI video module not to > > create the acpi_videoX sysfs interface and let's see if X server will > > pick up the intel_backlight one. > > Adding acpi_backlight=vendor to the kernel cmdline results in the > brightness controls not working from first boot, not just after a > suspend. That probably because X server now picks the toshiba_acpi interface instead of the intel_backlight one. A workaround from user space is to specify the backlight interface you want to use in xorg.conf, an example is here: https://bugs.debian.org/cgi-bin/bugreport.cgi?msg=78;att=0;bug=651741 Section "Device" Identifier "Intel Graphics" Driver "intel" Option "AccelMethod" "sna" Option "Backlight" "intel_backlight" Driver "intel" BusID "PCI:0:2:0" EndSection Alternatively, we can disable the acpi_video and toshiba_acpi interfaces in the kernel so that only intel_backlight is available. I'm not sure how to do this nicely, I've cc-ed platform x86 mailing list. Regards, Aaron > > Detailed test results: > > After fresh boot into 3.16-rc with acpi_backlight=vendor added to the > kernel cmdline > ls -l /sys/class/backlight > total 0 > lrwxrwxrwx 1 root root 0 Jul 31 21:38 intel_backlight -> > ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight > lrwxrwxrwx 1 root root 0 Jul 31 21:38 toshiba -> > ../../devices/LNXSYSTM:00/LNXSYBUS:00/TOS6208:00/backlight/toshiba > > Attempts to adjust brightness via user interfaces (system settings and > function keys) fail to change brightness. > > It remains possible to adjust brightness by directly writing to > /sys/class/backlight/intel_backlight/brightness but, as before, not by > writing to /sys/class/backlight/toshiba/brightness. > > After suspend and resume same test results. > > Regards, John -- 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
