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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/gpu/vkms.rst | |
parent | Initial commit. (diff) | |
download | linux-430c2fc249ea5c0536abd21c23382884005c9093.tar.xz linux-430c2fc249ea5c0536abd21c23382884005c9093.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'Documentation/gpu/vkms.rst')
-rw-r--r-- | Documentation/gpu/vkms.rst | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst new file mode 100644 index 000000000..61586fc86 --- /dev/null +++ b/Documentation/gpu/vkms.rst @@ -0,0 +1,110 @@ +.. _vkms: + +========================================== + drm/vkms Virtual Kernel Modesetting +========================================== + +.. kernel-doc:: drivers/gpu/drm/vkms/vkms_drv.c + :doc: vkms (Virtual Kernel Modesetting) + +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). + +- 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. + +Add Plane Features +------------------ + +There's lots of plane features we could add support for: + +- Real overlay planes, not just cursor. + +- Full alpha blending on all planes. + +- Rotation, scaling. + +- 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). + +For all of these, we also want to review the igt test coverage and make sure all +relevant igt testcases work on vkms. + +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: + +- Writeback connector. This is useful for testing compositors if you don't have + hardware with writeback support. + +- 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 +--------------- + +- Variable refresh rate/freesync support. This probably needs prime buffer + sharing support, so that we can use vgem fences to simulate rendering in + testing. Also needs support to specify the EDID. + +- 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". + +Atomic Check using eBPF +----------------------- + +Atomic drivers have lots of restrictions which are not exposed to userspace in +any explicit form through e.g. possible property values. Userspace can only +inquiry about these limits through the atomic IOCTL, possibly using the +TEST_ONLY flag. Trying to add configurable code for all these limits, to allow +compositors to be tested against them, would be rather futile exercise. Instead +we could add support for eBPF to validate any kind of atomic state, and +implement a library of different restrictions. + +This needs a bunch of features (plane compositing, multiple outputs, ...) +enabled already to make sense. |