[PATCH] drm/vkms: Extend todo

[Daniel Vetter <daniel.vetter@ffwll.ch>]

Typed up all the items Rodrigo capture at the vkms workshop at
xdc2018:

https://etherpad.net/p/vkms_todo

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>
---
 Documentation/gpu/vkms.rst | 87 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 85 insertions(+), 2 deletions(-)

diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
index 0a6ea6216e41..80cbe0759d3c 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 +22,86 @@ 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 testcases 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.
+
+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 fort:
+
+- 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".
-- 
2.19.0.rc2

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