KMS documentation for userspace

[Simon Ser]

Hi all,

With Wayland compositors and DRM leases, the number of DRM userspace
programs has increased (and will probably continue to increase).
However it's been pretty hard to find good DRM docs for userspace.

The resources currently available are:

- The kernel docs, although only the high level overview is useful to
  userspace.
- User-contributed tutorials, like [1] and [2].
- To help userspace understand hardware capabilities and limitations,
  I've recently started a DRM database dump project [3].

(Anything else I've missed?)

We still lack docs that describe how to properly use the KMS API and
the KMS properties. There is a deprecated list at [4], and another list
mixed with kernel structs at [5]. This is not great for userspace
developers.

So I wanted to know if there's interest from the kernel community to
maintain documentation for userspace? Or should userspace maintain its
own docs of the kernel API?

I don't know what would be the best place for these docs. If they live
in kernel doc comments, then references to kernel functions and
guidelines for kernel devs will appear (just like in the current docs).
If they live outside of the kernel source code or outside of the kernel
tree, they might get outdated.

Thoughts?

Thanks,

[1]: https://github.com/ascent12/drm_doc
[2]: https://gitlab.freedesktop.org/daniels/kms-quads
[3]: https://drmdb.emersion.fr/
[4]: https://01.org/linuxgraphics/gfx-docs/drm/gpu/drm-kms.html#standard-connector-properties
[5]: https://01.org/linuxgraphics/gfx-docs/drm/gpu/drm-kms.html#existing-kms-properties

--
Simon Ser
https://emersion.fr