646596485e
As it turns out, apparently some machines will actually leave additional
backlight functionality like dynamic backlight control on before the OS
loads. Currently we don't take care to disable unsupported features when
writing back the backlight mode, which can lead to some rather strange
looking behavior when adjusting the backlight.
So, let's fix this by just not reading back the current backlight mode on
initial enable. I don't think there should really be any downsides to this,
and this will ensure we don't leave any unsupported functionality enabled.
This should fix at least one (but not all) of the issues seen with DPCD
backlight support on fi-bdw-samus
v5:
* Just avoid reading back DPCD register - Doug Anderson
Signed-off-by: Lyude Paul <lyude@redhat.com>
Fixes: 867cf9cd73c3 ("drm/dp: Extract i915's eDP backlight code into DRM helpers")
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20211105183342.130810-4-lyude@redhat.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.