[PATCH v2] drm/vkms: update todo

Wed Oct 7 13:19:57 UTC 2020

On 10/06, Melissa Wen wrote:
> Drop issues already resolved in vkms:
> 
> - CRC API Improvements to [1] add igt test to check extreme alpha values
>   and [2] alpha blending;
> - [3] prime buffer sharing;
> - [4] writeback support;
> 
> On the other hand, we also found or thought about other improvements since
> the last update of this document:
> 
> - better support for IGT tests
> - improvements to writeback support
> - syzbot report
> 
> Finally, we reorder items by the assumed complexity.
> 
> [1] https://patchwork.freedesktop.org/series/55944/
> [2] https://patchwork.freedesktop.org/series/80823/
> [3] https://patchwork.freedesktop.org/series/63212/
> [4] https://patchwork.freedesktop.org/series/81177/
> 
> v2:
> - Link to syzbot dashboard
> 
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Rodrigo Siqueira <rodrigosiqueiramelo at gmail.com>
> Cc: Haneen Mohammed <hamohammed.sa at gmail.com>
> 
> Signed-off-by: Melissa Wen <melissa.srw at gmail.com>
> Acked-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> ---
>  Documentation/gpu/vkms.rst | 99 ++++++++++++++++++++------------------
>  1 file changed, 53 insertions(+), 46 deletions(-)
> 
> diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
> index 61586fc861bb..50b30dea0ba8 100644
> --- a/Documentation/gpu/vkms.rst
> +++ b/Documentation/gpu/vkms.rst
> @@ -10,36 +10,24 @@
>  TODO
>  ====
>  
> -CRC API Improvements
> ---------------------
> -
> -- Optimize CRC computation ``compute_crc()`` and plane blending ``blend()``
> -
> -- Use the alpha value to blend vaddr_src with vaddr_dst instead of
> -  overwriting it in ``blend()``.
> -
> -- Add igt test to check cleared alpha value for XRGB plane format.
> -
> -- Add igt test to check extreme alpha values i.e. fully opaque and fully
> -  transparent (intermediate values are affected by hw-specific rounding modes).
> -
> -Runtime Configuration
> ----------------------
> -
> -We want to be able to reconfigure vkms instance without having to reload the
> -module. Use/Test-cases:
> -
> -- Hotplug/hotremove connectors on the fly (to be able to test DP MST handling of
> -  compositors).
> +If you want to do any of the items listed below, please share your interest
> +with one of the VKMS maintainers.

Hi Melissa,

How about change "one of the VKMS maintainers" to "with VKMS
maintainers".

With the above change, everything else LGTM.

Reviewed-by: Rodrigo Siqueira <rodrigosiqueiramelo at gmail.com>

> -- Configure planes/crtcs/connectors (we'd need some code to have more than 1 of
> -  them first).
> +IGT better support
> +------------------
>  
> -- Change output configuration: Plug/unplug screens, change EDID, allow changing
> -  the refresh rate.
> +- Investigate: (1) test cases on kms_plane that are failing due to timeout on
> +  capturing CRC; (2) when running kms_flip test cases in sequence, some
> +  successful individual test cases are failing randomly.
>  
> -The currently proposed solution is to expose vkms configuration through
> -configfs.  All existing module options should be supported through configfs too.
> +- VKMS already has support for vblanks simulated via hrtimers, which can be
> +  tested with kms_flip test; in some way, we can say that VKMS already mimics
> +  the real hardware vblank. However, we also have virtual hardware that does
> +  not support vblank interrupt and completes page_flip events right away; in
> +  this case, compositor developers may end up creating a busy loop on virtual
> +  hardware. It would be useful to support Virtual Hardware behavior in VKMS
> +  because this can help compositor developers to test their features in
> +  multiple scenarios.
>  
>  Add Plane Features
>  ------------------
> @@ -55,34 +43,50 @@ There's lots of plane features we could add support for:
>  - Additional buffer formats, especially YUV formats for video like NV12.
>    Low/high bpp RGB formats would also be interesting.
>  
> -- Async updates (currently only possible on cursor plane using the legacy cursor
> -  api).
> +- Async updates (currently only possible on cursor plane using the legacy
> +  cursor api).
> +
> +For all of these, we also want to review the igt test coverage and make sure
> +all relevant igt testcases work on vkms.
> +
> +Prime Buffer Sharing
> +--------------------
>  
> -For all of these, we also want to review the igt test coverage and make sure all
> -relevant igt testcases work on vkms.
> +- Syzbot report - WARNING in vkms_gem_free_object:
> +  https://syzkaller.appspot.com/bug?extid=e7ad70d406e74d8fc9d0
> +
> +Runtime Configuration
> +---------------------
> +
> +We want to be able to reconfigure vkms instance without having to reload the
> +module. Use/Test-cases:
> +
> +- Hotplug/hotremove connectors on the fly (to be able to test DP MST handling
> +  of compositors).
> +
> +- Configure planes/crtcs/connectors (we'd need some code to have more than 1 of
> +  them first).
> +
> +- Change output configuration: Plug/unplug screens, change EDID, allow changing
> +  the refresh rate.
> +
> +The currently proposed solution is to expose vkms configuration through
> +configfs.  All existing module options should be supported through configfs
> +too.
>  
>  Writeback support
>  -----------------
>  
> -Currently vkms only computes a CRC for each frame. Once we have additional plane
> -features, we could write back the entire composited frame, and expose it as:
> +- The writeback and CRC capture operations share the use of composer_enabled
> +  boolean to ensure vblanks. Probably, when these operations work together,
> +  composer_enabled needs to refcounting the composer state to proper work.
>  
> -- Writeback connector. This is useful for testing compositors if you don't have
> -  hardware with writeback support.
> +- Add support for cloned writeback outputs and related test cases using a
> +  cloned output in the IGT kms_writeback.
>  
>  - As a v4l device. This is useful for debugging compositors on special vkms
>    configurations, so that developers see what's really going on.
>  
> -Prime Buffer Sharing
> ---------------------
> -
> -We already have vgem, which is a gem driver for testing rendering, similar to
> -how vkms is for testing the modeset side. Adding buffer sharing support to vkms
> -allows us to test them together, to test synchronization and lots of other
> -features. Also, this allows compositors to test whether they work correctly on
> -SoC chips, where the display and rendering is very often split between 2
> -drivers.
> -
>  Output Features
>  ---------------
>  
> @@ -93,7 +97,10 @@ Output Features
>  - Add support for link status, so that compositors can validate their runtime
>    fallbacks when e.g. a Display Port link goes bad.
>  
> -- All the hotplug handling describe under "Runtime Configuration".
> +CRC API Improvements
> +--------------------
> +
> +- Optimize CRC computation ``compute_crc()`` and plane blending ``blend()``
>  
>  Atomic Check using eBPF
>  -----------------------
> -- 
> 2.28.0
> 

-- 
Rodrigo Siqueira
https://siqueira.tech
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