about weston behavior if DRM driver don't expose supported modifiers

[Esaki Tomohito]

Hello,

A board (arm64 arch) DRM kernel driver doesn't expose supported DRM
modifiers (hardware supports linear only), so I suggested following
patch:

https://patchwork.kernel.org/patch/10936631/

The driver maintainer (Laurent CC'd) replied:

> I don't think the right solution is to expose the linear modifier from
> all drivers that don't otherwise support modifiers. We should instead
> fix it either in Weston, and treat drivers that don't support the
> modifiers API as supporting the linear modifier only, or in the DRM/KMS
> core by reporting the linear modifier for drivers that don't explicitly
> support modifiers.

I would like to know if you have any opinion on this comment.
Do we need fix weston?

Background:
I want to use sprite plane. The GPU hardware is a different device from
the display DRM hardware. The GPU driver advertises support for
DRM_FORMAT_MOD_LINEAR modifier, but display driver currently doesn't
support DRM modifiers. Currently in weston, if a client attaches a
buffer with DRM_FORMAT_MOD_LINEAR modifier via linux-dmabuf protocol,
since the attached buffer modifier is different to plane modifier,
weston draws surface in primary plane not sprite plane.

Thanks.

-- 
--------------------------
Tomohito Esaki
etom at igel.co.jp