Re: [Buildroot] [PATCH] package/cog: add libgbm as dependency when building with DRM support

From: Thomas Petazzoni via buildroot <buildroot@buildroot.org>
To: Alexandru Ardelean <ardeleanalex@gmail.com>
Cc: Adrian Perez de Castro <aperez@igalia.com>, buildroot@buildroot.org
Subject: Re: [Buildroot] [PATCH] package/cog: add libgbm as dependency when building with DRM support
Date: Fri, 22 Jul 2022 08:59:59 +0200	[thread overview]
Message-ID: <20220722085959.5fd21e9f@windsurf> (raw)
In-Reply-To: <CA+U=Dsr60t8_dfdAL7CAbtbGL2i8+WyWD-byyEFQg=vpc5dHBg@mail.gmail.com>

On Fri, 22 Jul 2022 09:38:02 +0300
Alexandru Ardelean <ardeleanalex@gmail.com> wrote:

> > > Of course, this aspect should be in a different patch: your change to
> > > add "libgbm" in the DEPENDENCIES variable is really a fix, while my
> > > proposed change in the Config.in file is really an improvement, that
> > > will allow using Cog on libgbm-capable platforms that don't use mesa3d
> > > as their OpenGL/libgbm implementation.  
> 
> Apologies for not including this part in the second email.
> So, at least cog 0.12.4 that is currently packaged in Buildroot
> doesn't seem to support (yet)

It's not about whether cog supports it, but whether it uses it.

> BR2_PACKAGE_LIBGBM_HAS_FEATURE_FORMAT_MODIFIER_PLANE_COUNT
> and
> BR2_PACKAGE_LIBGBM_HAS_FEATURE_DMA_BUF
> 
> at least what 'package/opengl/libgbm/Config.in ' mentions:
> - i can't see any use of gbm_device_get_format_modifier_plane_count in
> cog 0.12.4

Correct, but it is using:

gbm_bo_get_plane_count
gbm_bo_get_handle_for_plane
gbm_bo_get_stride_for_plane

etc. which are also related to the same "plane" support. Actually, I'm
wondering if the name
BR2_PACKAGE_LIBGBM_HAS_FEATURE_FORMAT_MODIFIER_PLANE_COUNT was really
the best.

We do have versions of libgbm that don't have any support for this
plane API.

> - i can't see any use of gbm_bo_get_fd in cog 0.12.4
> 
> And also looking now through the code, I see that EGL is used in all 3
> platforms (DRM, X11 and Wayland).
> Buildroot builds for Wayland and DRM (AFAICT).
> So, I guess libegl is explicitly required for the DRM platform.

Correct.

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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