chipset: Ironlake (Intel Core i5 U430M)
kernel: 2.6.38-rc5+ (drm-intel-fixes 811779a0fbd23035872d1fc8f2d1baf550a94f10)
distribution: Fedora Rawhide
machine: Sony Vaio VPCY2190X (2nd-generation Y series, customized-to-order)
connector: LVDS (internal panel)
1. Boot to graphical mode
2. Log in
3. Try setting brightness with function keys or xbacklight
The backlight brightness controls, both GNOME (with Fn keys) and xbacklight, do not actually affect the LCD brightness at all, though changing the backlight setting in one reflects the value read by the other. "xset dpms force off" does work.
I've tried booting with acpi_backlight=vendor, but that only results in no backlight control available from userspace whatsoever (running xbacklight returns nothing, instead of the current backlight setting).
Created attachment 43501 [details]
Created attachment 43502 [details]
Created attachment 43503 [details]
Created attachment 43504 [details]
*** This bug has been marked as a duplicate of bug 34437 ***
Reported fix does not actually work
Created attachment 49035 [details] [review]
mjg's i915 native GPU backlight control patch from linux-next
Applying Matthew Garrett's latest iteration of the i915 native backlight patch,
already in linux-next, on top of Linus' 3.0rc7 fixes the issue for me.
Hope to see this incorporated soon (the native backlight infrastructure is already in Linus' tree, it's only the per-driver implementations that have not landed).
Is there a way to disable *both* backlight=video and backlight=vendor, and leave only the native backlight interface present? Right now I have both acpi_video0 and intel-backlight, and GNOME Power Manager prefers the former.
Patch has been applied by keithp a few releases back
on May 29, 2016 at 17:15:17.
(provided by the Example extension).