123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110 |
- .. _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.
|