drm2 regression: backlight adjustment on ivybridge no longer works

[Andrew Wilcox]

Ranjan1018 . sent: 27 January 2015 23:42:
> my Samsung laptop has an Intel IvyBridge: [snip]
> The regression was introduced in r277487.
> The backlight adjustment works in FreeBSD 11.0-CURRENT r277395, r277486
> but not in r277487, r277534 and r277639.

Hrm.  That is interesting.  A few questions I have then.

- What happens if you set drm.i915.invert_brightness to -1 in kenv(1) or /boot/loader.conf?

- What happens if you set drm.i915.invert_brightness to 1 in kenv(1) or /boot/loader.conf?

- What version of graphics/libdrm do you have installed?  Did you rebuild it after installing the new kernel?  (This shouldn't be necessary, but I am trying to gather all details.)

Let's start there and see if we can pin down a cause.

Best,
Andrew
--
Andrew Wilcox, C/C++/Python developer, kernel hacker
Blog:   http://blog.foxkit.us/  WWW: http://foxkit.us/
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