projects / linux-2.6-block.git / blame
| Commit | Line | Data |
|---|---|---|
| ad9ff96f HM |
1 | .. _vkms: |
| 2 | ||
| 3 | ========================================== | |
| 4 | drm/vkms Virtual Kernel Modesetting | |
| 5 | ========================================== | |
| 6 | ||
| 7 | .. kernel-doc:: drivers/gpu/drm/vkms/vkms_drv.c | |
| 8 | :doc: vkms (Virtual Kernel Modesetting) | |
| 9 | ||
| 10 | TODO | |
| 11 | ==== | |
| 12 | ||
| d717c6df DV |
13 | CRC API Improvements |
| 14 | -------------------- | |
| ad9ff96f HM |
15 | |
| 16 | - Optimize CRC computation ``compute_crc()`` and plane blending ``blend()`` | |
| 17 | ||
| 18 | - Use the alpha value to blend vaddr_src with vaddr_dst instead of | |
| 19 | overwriting it in ``blend()``. | |
| 20 | ||
| 21 | - Add igt test to check cleared alpha value for XRGB plane format. | |
| 22 | ||
| 23 | - Add igt test to check extreme alpha values i.e. fully opaque and fully | |
| 24 | transparent (intermediate values are affected by hw-specific rounding modes). | |
| d717c6df DV |
25 | |
| 26 | Vblank issues | |
| 27 | ------------- | |
| 28 | ||
| 29 | Some IGT test cases are failing. Need to analyze why and fix the issues: | |
| 30 | ||
| 31 | - plain-flip-fb-recreate | |
| 32 | - plain-flip-ts-check | |
| 33 | - flip-vs-blocking-wf-vblank | |
| 34 | - plain-flip-fb-recreate-interruptible | |
| 35 | - flip-vs-wf_vblank-interruptible | |
| 36 | ||
| 37 | Runtime Configuration | |
| 38 | --------------------- | |
| 39 | ||
| 40 | We want to be able to reconfigure vkms instance without having to reload the | |
| 41 | module. Use/Test-cases: | |
| 42 | ||
| 43 | - Hotplug/hotremove connectors on the fly (to be able to test DP MST handling of | |
| 44 | compositors). | |
| 45 | ||
| 46 | - Configure planes/crtcs/connectors (we'd need some code to have more than 1 of | |
| 47 | them first). | |
| 48 | ||
| 49 | - Change output configuration: Plug/unplug screens, change EDID, allow changing | |
| 50 | the refresh rate. | |
| 51 | ||
| 52 | The currently proposed solution is to expose vkms configuration through | |
| 53 | configfs. All existing module options should be supported through configfs too. | |
| 54 | ||
| 55 | Add Plane Features | |
| 56 | ------------------ | |
| 57 | ||
| 58 | There's lots of plane features we could add support for: | |
| 59 | ||
| 60 | - Real overlay planes, not just cursor. | |
| 61 | ||
| 62 | - Full alpha blending on all planes. | |
| 63 | ||
| 64 | - Rotation, scaling. | |
| 65 | ||
| 66 | - Additional buffer formats, especially YUV formats for video like NV12. | |
| 67 | Low/high bpp RGB formats would also be interesting. | |
| 68 | ||
| 69 | - Async updates (currently only possible on cursor plane using the legacy cursor | |
| 70 | api). | |
| 71 | ||
| 72 | For all of these, we also want to review the igt test coverage and make sure all | |
| 73 | relevant igt testcases work on vkms. | |
| 74 | ||
| 75 | Writeback support | |
| 76 | ----------------- | |
| 77 | ||
| 78 | Currently vkms only computes a CRC for each frame. Once we have additional plane | |
| 79 | features, we could write back the entire composited frame, and expose it as: | |
| 80 | ||
| 81 | - Writeback connector. This is useful for testing compositors if you don't have | |
| 82 | hardware with writeback support. | |
| 83 | ||
| 84 | - As a v4l device. This is useful for debugging compositors on special vkms | |
| 85 | configurations, so that developers see what's really going on. | |
| 86 | ||
| 87 | Prime Buffer Sharing | |
| 88 | -------------------- | |
| 89 | ||
| 90 | We already have vgem, which is a gem driver for testing rendering, similar to | |
| 91 | how vkms is for testing the modeset side. Adding buffer sharing support to vkms | |
| 92 | allows us to test them together, to test synchronization and lots of other | |
| 93 | features. Also, this allows compositors to test whether they work correctly on | |
| 94 | SoC chips, where the display and rendering is very often split between 2 | |
| 95 | drivers. | |
| 96 | ||
| 97 | Output Features | |
| 98 | --------------- | |
| 99 | ||
| 100 | - Variable refresh rate/freesync support. This probably needs prime buffer | |
| 101 | sharing support, so that we can use vgem fences to simulate rendering in | |
| 102 | testing. Also needs support to specify the EDID. | |
| 103 | ||
| 104 | - Add support for link status, so that compositors can validate their runtime | |
| 105 | fallbacks when e.g. a Display Port link goes bad. | |
| 106 | ||
| 107 | - All the hotplug handling describe under "Runtime Configuration". | |
| 108 | ||
| 109 | Atomic Check using eBPF | |
| 110 | ----------------------- | |
| 111 | ||
| 112 | Atomic drivers have lots of restrictions which are not exposed to userspace in | |
| 113 | any explicit form through e.g. possible property values. Userspace can only | |
| 114 | inquiry about these limits through the atomic IOCTL, possibly using the | |
| 115 | TEST_ONLY flag. Trying to add configurable code for all these limits, to allow | |
| 116 | compositors to be tested against them, would be rather futile exercise. Instead | |
| 117 | we could add support for eBPF to validate any kind of atomic state, and | |
| 118 | implement a library of different restrictions. | |
| 119 | ||
| 120 | This needs a bunch of features (plane compositing, multiple outputs, ...) | |
| 121 | enabled already to make sense. |