[PATCH] drm/connector: hdmi: Add a link bpc property

[Michel Dänzer]

On 01.08.25 12:17, Marius Vlad wrote:
> From: Derek Foreman <derek.foreman at collabora.com>
> 
> Add a way to know the actual bpc of a running link.
> 
> Drivers might change the current bpc link value due to changes in mode
> line or refresh rates. For example when enabling VRR the underlying
> hardware might not be able sustain the same bandwidth for a particular
> mode line, and it might attempt to lower the bpc. Another example can be
> found when switching the color output format, part of YUV420 fallback.
> 
> This means we might be displaying a stale bpc value although it was
> modified for different reasons -- like a refresh rate or an output
> color format.
> 
> This patch introduces a new property 'link bpc' that user-space can
> use to get the current bpc value of a running link. In the same
> time this would allow user-space set up bpc using 'max_bpc' property.

With my Wayland compositor developer hat on, what I want to know the most isn't the physical link bpc but the "effective" bpc, i.e. how many bits of information can actually be transferred to the display, taking things like dithering into account.

(Not saying the physical link bpc couldn't also be useful for something, I'm not aware of any use for it offhand though)


-- 
Earthling Michel Dänzer       \        GNOME / Xwayland / Mesa developer
https://redhat.com             \               Libre software enthusiast