Re: [Buildroot] [PATCH v2] package/cog: add libgbm as dependency when building with DRM support

From: Thomas Petazzoni via buildroot <buildroot@buildroot.org>
To: "Michael Nosthoff" <michael@nosthoff.rocks>
Cc: aperez@igalia.com, Alexandru Ardelean <ardeleanalex@gmail.com>,
	buildroot@buildroot.org
Subject: Re: [Buildroot] [PATCH v2] package/cog: add libgbm as dependency when building with DRM support
Date: Sun, 24 Jul 2022 16:53:27 +0200	[thread overview]
Message-ID: <20220724165327.5b22ff1c@windsurf> (raw)
In-Reply-To: <48-62dd4800-5-54f5770@160071985>

Hello Michael,

On Sun, 24 Jul 2022 15:25:00 +0200
"Michael Nosthoff" <michael@nosthoff.rocks> wrote:

> I'm currently maintaining an external package for the newest ti-sgx-um version which provides
> (i think) a newer/more complete version of libegl/libgbm. For this I currently have to patch
> the cog package but the output is working fine with the drm backend.

Wow, do you have that available somewhere? I'm also working on a
project that uses ti-sgx, we're also working on updating it to the
latest version from TI, and we had issues with libgbm being
insufficient to run Cog.

> Is there a way to find out which features a certain libegl/libgbm provides? Maybe I can then pick-up
> the work on bumping the ti-sgx-um/km packages again to bring them to a more recent version.

It is explained in package/opengl/libgbm/Config.in:

# gbm implementations should select
# BR2_PACKAGE_LIBGBM_HAS_FEATURE_FORMAT_MODIFIER_PLANE_COUNT if they
# provide the format modifier plane count feature. This API was
# initially introduced in mesa3d version 17. A gbm implementation
# provides this feature if it is implement function
# gbm_device_get_format_modifier_plane_count.
config BR2_PACKAGE_LIBGBM_HAS_FEATURE_FORMAT_MODIFIER_PLANE_COUNT
        bool
        depends on BR2_PACKAGE_HAS_LIBGBM

# gbm implementations should select
# BR2_PACKAGE_LIBGBM_HAS_FEATURE_DMA_BUF if they provide the dma
# buffer feature. This API was initially introduced in mesa3d version
# 10. A gbm implementation provides this feature if it is implement
# function gbm_bo_get_fd.
config BR2_PACKAGE_LIBGBM_HAS_FEATURE_DMA_BUF
        bool
        depends on BR2_PACKAGE_HAS_LIBGBM

So basically, you can readelf on libgbm.so, and based on the functions
that it provides, decide which of the above feature flag your ti-sgx-um
package should select.

If you need some help on this, feel free to get in touch on IRC (if
you're not already there), I'll be happy to have a look as I'm
interested in Cog + ti-sgx-um.

Thanks!

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