ACK/Cmnt: [SRU] [F/G/Unstable/OEM-5.6] [PATCH 0/3] Enable brightness control on HP DreamColor panel

Stefan Bader stefan.bader at
Thu Oct 8 09:07:05 UTC 2020

On 07.10.20 13:53, Kai-Heng Feng wrote:
> BugLink:
> [Impact]
> Brightness on HP DreamColor panel, which can be found on new HP Zbook
> Studio, cannot be changed.
> [Fix]
> Let DRM know the panel should use DPCD instead of PWM to control
> backlight.
> [Test]
> With the patch applied, we can change the brightness on HP Zbook Studio.
> [Regression Potential]
> If there's any panel in the quirk list depends on checking brightness
> control capability then this change will have an impact. However it's
> rather unlikely because it defeats the purpose of the quirk list.
> Kai-Heng Feng (2):
>   UBUNTU: SAUCE: drm/i915/dpcd_bl: Skip testing control capability with
>     force DPCD quirk
>   UBUNTU: SAUCE: drm/dp: HP DreamColor panel brigntness fix
> Lyude Paul (1):
>   drm/i915/dpcd_bl: Unbreak enable_dpcd_backlight modparam
>  drivers/gpu/drm/drm_dp_helper.c                       | 1 +
>  drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 9 ++++++---
>  2 files changed, 7 insertions(+), 3 deletions(-)
For Focal I am not really happy to ack because it seems to add a lot of new
SAUCE which could mean it is not accepted upstream or is rather new that there
was not much baking time. All things that do not really comply with the concept
of a stable release.

Though the first patch now is upstream:

commit d082119f4277ff4a63e44d293864aa9f2112b217
Author: Lyude Paul <lyude at>
Date:   Mon Apr 13 17:44:06 2020 -0400
    drm/i915/dpcd_bl: Unbreak enable_dpcd_backlight modparam

So the following should be put before your sign-off when things get committed:

(cherry picked from commit d7fb38ae36a2dc97924b075ad1d1a88792777ea9)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi at>

(cherry picked from commit d082119f4277ff4a63e44d293864aa9f2112b217)
Signed-off-by: ...

The other two patches, at least they appear harmless enough, are you planning on
upstreaming those?

For now, as this looks isolated enough...

Acked-by: Stefan Bader <stefan.bader at>

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