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authorDaniel Vetter <daniel.vetter@ffwll.ch>2018-10-03 15:21:03 +0200
committerDaniel Vetter <daniel.vetter@ffwll.ch>2018-10-03 18:19:41 +0200
commitd717c6df3040abe6456b790e6901e1b98f83c201 (patch)
tree13292633e8d5e2f739694f00cc3d6bcb5a5672f2 /Documentation/gpu/vkms.rst
parentc5e69ab35c0d7069ad860c5cb44a5986e2322160 (diff)
drm/vkms: Extend todo
Typed up all the items Rodrigo capture at the vkms workshop at xdc2018: https://etherpad.net/p/vkms_todo v2: Review from Rodrigo. - Add eBPF for atomic check, I forgot it. - Improve spelling. Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> Cc: Gustavo Padovan <gustavo@padovan.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Sean Paul <sean@poorly.run> Cc: Haneen Mohammed <hamohammed.sa@gmail.com> Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com> Reviewed-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com> Link: https://patchwork.freedesktop.org/patch/msgid/20181003132103.29309-1-daniel.vetter@ffwll.ch
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diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
index 0a6ea6216e41..7dfc349a4508 100644
--- a/Documentation/gpu/vkms.rst
+++ b/Documentation/gpu/vkms.rst
@@ -10,8 +10,8 @@
TODO
====
-CRC API
--------
+CRC API Improvements
+--------------------
- Optimize CRC computation ``compute_crc()`` and plane blending ``blend()``
@@ -22,3 +22,100 @@ CRC API
- Add igt test to check extreme alpha values i.e. fully opaque and fully
transparent (intermediate values are affected by hw-specific rounding modes).
+
+Vblank issues
+-------------
+
+Some IGT test cases are failing. Need to analyze why and fix the issues:
+
+- plain-flip-fb-recreate
+- plain-flip-ts-check
+- flip-vs-blocking-wf-vblank
+- plain-flip-fb-recreate-interruptible
+- flip-vs-wf_vblank-interruptible
+
+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.