I'm adding features to VKMS! What would you like to see?

[Thomas Zimmermann]

Hi

Am 28.07.22 um 20:54 schrieb Jim Shargo:
> Hi Wayland folks!
> 
> TL;DR: I'm working on extending VKMS and wanted feedback from other
> compositor/wayland devs.

Thanks for helping!

> 
> // Background
> 
> I work on the ChromeOS compositor, and recently I've been doing a
> bunch of stuff to improve our testing setup. At the moment, my main
> focus is improving our ability to write integration tests against
> DRM/KMS.
> 
> It's pretty tricky to get right. Working with mocks of DRM loses all
> the useful helpers that live within the kernel, which would need to be
> rewritten (and kept up-to-date) in userspace. Stuff like writeback
> support would be even harder.
> 
> Earlier this year, VKMS came up as a potential solution. I was happy
> to see that Weston is already using it. I've started thinking about
> what features from the wild we'd need, and started digging into the
> code.
> 
> // Current Status
> 
> I recently sent out my first patchset, which will let userspace build
> their own DRM drivers with ConfigFS. This implicitly adds support for
> multi-display setups which were impossible to test before. This also
> allows for multiple virtual DRM drivers to be created and used at the
> same time, which may increase test parallelism? Haven't tried it yet.
> 
> v1 patchset: https://patchwork.kernel.org/project/dri-devel/list/?series=662676
> cover letter: https://lists.freedesktop.org/archives/dri-devel/2022-July/365647.html
> 
> // Rough Plans
> 
> The big features I want to target with this work are:
>    - Multi-display and movable planes. This is mostly covered by the
> ConfigFS changes.
>    - Hot plugging.
>    - Color, color management and HDR. Loads of new formats, support for
> color properties not currently implemented. Making sure writeback
> buffers are useful for this.
>    - Improve IGT testing for VKMS (for new features and existing skipped tests)
> 
> // Questions
> 
>    - What VKMS features could help your testing the most?
>    - How much do you care about writeback buffer support vs CRC checks
> in tests atm?
>    - What kinds of bugs do you get around DRM/KMS?
>    - Any thoughts in general?

I think damage handling might be useful. Userspace tests can set damage 
areas and readback the the results or CRC checksum. See the kernel's 
drm_plane_enable_fb_damage_clips() and struct drm_atomic_helper_damage_iter.

Best regards
Thomas


> 
> Thanks!
> -- Jim

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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