[Bug 111202] Intel_backlight fails to change eDP1 brightness on Dell Precision 5540 (Coffeelake)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=111202

Arcadiy Ivanov <arcadiy at ivanov.biz> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|NOTABUG                     |---

--- Comment #11 from Arcadiy Ivanov <arcadiy at ivanov.biz> ---
Ha! Sorry, it is a bug, reopening. The reason I had the
`enable_dpcd_backlight=1` on in the first place was because without it external
monitors failed to go to "energy saving" mode without it. Removing it causes
eDP1 on 5540 brightness to be controllable but external monitors (via TB hub)
apparently failed to go to sleep.

So:

enable_dpcd_backlight=1:
 7510:
      eDP1 - brightness controllable, energy savings mode works
      external - N/A, energy savings mode works
 5540:
      eDP1 - brightness NOT controllable, energy savings mode works
      external - N/A, energy savings mode works

enable_dpcd_backlight=0:
 7510:
      eDP1 - brightness controllable, energy savings mode works
      external - N/A, energy savings mode DOES NOT work
 5540:
      eDP1 - brightness controllable, energy savings mode works
      external - N/A, energy savings DOES NOT mode works

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