[Bug 82634] [snb] backlight issue on TOSHIBA PORTEGE R830 after suspend/resume

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=82634

--- Comment #15 from Sylvain Pasche <sylvain.pasche at gmail.com> ---
Hi Hans,

(In reply to Hans de Goede from comment #14)
> Hmm, what does "ls /sys/class/backlight" give as output with the latest F-22
> kernels without anything on the kernel commandline? And what are the problem
> symptoms when not having anything on the kernel commandline ? Does
> brightness control after boot work then? And what about after suspend/resume?

So, with kernel 4.0.4-301.fc22.x86_64 and nothing specific on the kernel
command line:
After boot, these two interfaces are available:
ls -l /sys/class/backlight/
lrwxrwxrwx. 1 root root 0 May 26  2015 acpi_video0 ->
../../devices/pci0000:00/0000:00:02.0/backlight/acpi_video0
lrwxrwxrwx. 1 root root 0 May 26  2015 intel_backlight ->
../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight

I can change the brightness on both.

After a suspend+resume:

  The backlight is turned on.
  changing brightness of acpi_video0 has no effect
  changing brightness of intel_backlight works

> Can you also try booting without "video.use_native_backlight=1" and with:
> 
> acpi_osi="!Windows 2012"
> 
> on the kernel commandline?

I tried that and I have the same behavior as above.

Gnome 3.16 gives priority on the acpi_video0 (firmware) interface over
intel_backlight (raw), so I can't change the brightness using Gnome after
suspend+resume.

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