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This page describes how to use the kmsxx library and its Python bindings to test DRM/KMS drivers.

Setting up kmsxx


kmsxx has a number of dependencies:

  • Python 3
  • cmake (minimum version 2.8.11)
  • a current build of libdrm; if your version is older than a couple of days, it is recommended to build a new one.
  • a C++ compiler supporting C++11

Getting the source code

  1. Check out kmsxx from https://github.com/tomba/kmsxx
  2. Check out the pybind11 submodule: git submodule update --init

Building kmsxx

  1. mkdir build && cd build && cmake ..
  2. make -j4

For mode detailed instructions see the README.md file in https://github.com/tomba/kmsxx/blob/master/README.md.

Using kmsxx with the Python bindings

Warning Warning: The Python bindings in mainline kmsxx are not complete. An more comprehensive set can be found here: https://github.com/uli/kmsxx/tree/topic-bindings

It is now possible to access the driver API through kmsxx from Python:

# PYTHONPATH=build/py/:py/ python3
Python 3.4.2 (default, Oct  8 2014, 14:47:30) 
[GCC 4.9.1] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pykms
>>> card = pykms.Card()
>>> conn = card.get_first_connected_connector()
>>> crtc = conn.get_current_crtc()
>>> crtc.mode.name

Automated testing

A version of kmsxx that adds a handful of automated tests can be found here: https://github.com/uli/kmsxx/tree/autotest.

Invoke the test suite using bash run_tests.sh. The output should look something like this:

Testing connector VGA-1
atomic_flip.py  PASS
atomic_set_plane.py  FAIL
atomic_small_dest.py  PASS
atomic_small_fb.py  PASS
fb_large.py  PASS
fb_small.py  PASS
mode_invalid.py  PASS
mode_reset.py  PASS
mode_set_all.py  PASS

9 passed, 1 failed, 0 skipped

The test suite will exit with an error code if any tests have failed.

By default, tests are performed using the first available connector. It is possible to specify a different connector on the command line: bash run_tests.sh 1, for instance, will use the second connector.

Fences testing

A version of kmsxx that includes tests for fences is available in the swsync branch of http://git.ideasonboard.com/renesas/kmsxx.git.

The fences test script is written in Python and named sync.py. It queues page flips with an in fence and arms a 500ms timer that signals the fence. The page flip handler then verifies that the flip doesn't complete before the timer fires.

The test uses the kernel sw_sync driver to signal fences in software, avoiding dependencies on other devices. The sw_sync driver must be compiled in the kernel (by enabling the CONFIG_SW_SYNC kernel option), and debugfs mounted on /sys/kernel/debug/.

If the test works, you will get an output similar to

# ./sync.py
--> timeout None
flipping with fence @1, timeline is @0
adding timer 11.729406
--> timeout 0.49938235800000008
fireing timer 11.729406
signaling timeline @0
--> timeout None
flipping with fence @3, timeline is @2
adding timer 12.246879
--> timeout 0.49987063900000095
fireing timer 12.246879
signaling timeline @2
--> timeout None
flipping with fence @5, timeline is @4
adding timer 12.750432
--> timeout 0.49989679999999836
fireing timer 12.750432
signaling timeline @4
--> timeout None
flipping with fence @7, timeline is @6
adding timer 13.254087
--> timeout 0.49990999899999977

If the DRM driver doesn't support in fences, the page flip will complete too soon and the test should throw an exception:

# ./sync.py
--> timeout None
flipping with fence @1, timeline is @0
adding timer 41.450282
--> timeout 0.4993602780000046
terminate called after throwing an instance of 'pybind11::error_already_set'
  what():  RuntimeError: Page flip 1 for fence 1 complete before timeline (0)!

  ./sync.py(67): handle_page_flip
  ./sync.py(157): readdrm
  ./sync.py(175): main
  ./sync.py(180): <module>


By default, the test uses the first connected connector. A specific connector can be selected by name on the command line: ./sync.py VGA-1.