[Intel-gfx] Developing a new backlight driver for specific OLED screen

[Lyude Paul]

On Fri, 2022-09-09 at 15:49 +0000, Aurélien wrote:
> Hi, 
> 
> > + dri-devel mailing list that looks more appropriated.
> > + Hans and Lyude who were recently working to standardize some of the
> > backlight stuff.
> 
> Thank you for these contacts. I'll try there if I need.
> 
> > I don't believe you want to use the i915 API, but move the common functions
> > to the drm subsystem itself and then reuse as a drm device.
> 
> If there is enough generic code I'll do everything with the DRM API. Unfortunately I can't spend too much time in order to generalize the i915 common functions.
> 
> > Aurélien, are you aware of drivers/gpu/drm/display/drm_dp_helper.c and
> > all the functions around struct dp_aux_backlight and struct
> > drm_edp_backlight_info?
> 
> Not yet. Since I'm not familiar with GPU/display drivers I didn't know what could be a good starting point. 
> Indeed I already checked the intel_dp_aux_backlight.c code. That's why I told about using the "i915 API code" at first. But since this display is independent from the GPU i didn't want to link both code. 
> Then that's a really good point if there is already an independant API. I'll have a look this evening.
> 
> > Does the display use some proprietary, non-VESA DPCD registers? There's
> > already some of that in i915 for Intel proprietary interfaces.
> 
> For sure. It's an OLED display. Thus there is no backlight. It uses specific registers to control the brightness of the screen.
> Unfortunately I guess the mechanism is not shared with many OLED displays...
> 
> Thank you for your help.

Seems like we've got a pretty good argument for renaming this from backlight
to something else at some point. FWIW, the word backlight is sometimes used
around these parts simply to describe controlling the brightness of an OLED
screen.

> 
> Aurélien
> 

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat