[PATCH v3 0/5] drm/gma500: Backlight handling changes

[Patrik Jakobsson]

On Sat, Sep 17, 2022 at 10:59 PM Hans de Goede <hdegoede at redhat.com> wrote:
>
> Hi All,
>
> Here is a patch-series changing gma500's backlight handling to match
> the changes done to the other major x86 GPU drivers in the just landed
> backlight detection refactor patch series:
> https://lore.kernel.org/dri-devel/261afe3d-7790-e945-adf6-a2c96c9b1eff@redhat.com/
>
> The main goal is here is to only register one backlight class device instead
> of registering both "acpi_video0" and "psb-bl" backlight class devices;
> in preparation for implementing the new backlight userspace-API from:
> https://lore.kernel.org/dri-devel/b61d3eeb-6213-afac-2e70-7b9791c86d2e@redhat.com/

Hi Hans,

Quite some time ago I wrote a backlight driver [1] for a MacBook to
work around an issue in the i915 driver. My driver spoke directly to
an external backlight driver chip. By doing so I could turn off the
signal coming from the GPU and instead program my own PWM value
directly. I remember it being a bit tricky to make my driver get
priority over the i915 driver. Not sure what the actual issue was but
I did get it to work properly in the end (perhaps with an xorg.conf
change).

I understand that this is a corner case but I'm just curious how/if
this can be handled with the new API. Is it possible to kick out an
existing non-acpi backlight driver if you know yours is better?

[1] https://github.com/patjak/mba6x_bl

>
> Changes in v2:
> - Add "Use backlight_get_brightness() to get the brightness" patch
>
> Changes in v3:
> - Fix unused variable warnings when CONFIG_BACKLIGHT is not selected by
>   marking the 2 variables as  __maybe_unused.

This looks good to me. I don't have access to my DIM setup in a couple
of days so please push these yourself if possible.

For the entire series:
Acked-by: Patrik Jakobsson <patrik.r.jakobsson at gmail.com>

>
> Regards,
>
> Hans
>
>
> Hans de Goede (5):
>   drm/gma500: Refactor backlight support (v2)
>   drm/gma500: Change registered backlight device type to raw/native
>   drm/gma500: Use backlight_get_brightness() to get the brightness
>   drm/gma500: Don't register backlight when another backlight should be
>     used
>   drm/gma500: Call acpi_video_register_backlight()
>
>  drivers/gpu/drm/gma500/backlight.c       | 102 +++++++++++++++--------
>  drivers/gpu/drm/gma500/cdv_device.c      |  50 ++---------
>  drivers/gpu/drm/gma500/oaktrail_device.c |  65 ++-------------
>  drivers/gpu/drm/gma500/opregion.c        |   6 +-
>  drivers/gpu/drm/gma500/psb_device.c      |  73 +---------------
>  drivers/gpu/drm/gma500/psb_drv.c         |  15 +---
>  drivers/gpu/drm/gma500/psb_drv.h         |  13 +--
>  7 files changed, 97 insertions(+), 227 deletions(-)
>
> --
> 2.37.3
>