Re: [PATCH] drm: DON'T require each CRTC to have a unique primary plane

From: Paul Cercueil
Date: Mon Mar 29 2021 - 11:40:04 EST




Le lun. 29 mars 2021 à 17:35, Maxime Ripard <maxime@xxxxxxxxxx> a écrit :
On Mon, Mar 29, 2021 at 04:15:28PM +0100, Paul Cercueil wrote:
Hi Maxime,

Le lun. 29 mars 2021 à 16:07, Maxime Ripard <maxime@xxxxxxxxxx> a écrit :
> On Sat, Mar 27, 2021 at 11:22:14AM +0000, Paul Cercueil wrote:
> > The ingenic-drm driver has two mutually exclusive primary planes
> > already; so the fact that a CRTC must have one and only one primary
> > plane is an invalid assumption.
>
> I mean, no? It's been documented for a while that a CRTC should only
> have a single primary, so I'd say that the invalid assumption was that
> it was possible to have multiple primary planes for a CRTC.

Documented where?

I did read the doc of "enum drm_plane_type" in <drm/drm_plane.h>, and the
DRM_PLANE_TYPE_PRIMARY describes my two planes, so I went with that.

At least since 4.9, this was in the documentation generated for DRM:
https://elixir.bootlin.com/linux/v4.9.263/source/drivers/gpu/drm/drm_plane.c#L43

Ok, I read that as "all drivers should provide AT LEAST one primary plane per CRTC", and not as "all drivers should provide ONE AND ONLY ONE primary plane per CRTC". My bad.

-Paul