The VSP DU Writeback node is a prototype stage extension to the VSP, which at this time requires manual testing.
Two terminals on the target are required, one to generate frames on the display, and one to capture the output.
Any application or method which generates images on the display pipeline should be suitable for the test. For this test, kmstest has been used. This is part of the DRM libraries and can be built following the instructions at R-Car/Tests:KMS-modetest
The writeback device node exposes a V4L2 video capture device node and any application suitable for grabbing frames from these devices can be used. For the purposes of this test we will use the utility yavta which is available at http://git.ideasonboard.org/?p=yavta.git
A writeback capture test
Identify the writeback capture video device node using sysfs
- grep -l fea38000 /sys/class/video4linux/video*/name
This, for instance, will return "/sys/class/video4linux/video28/name" which will show video28 as the node for /dev/
Execute the following command examples in parallel
- kmstest --sync --flip
- yavta -I -c30 -n8 -f RGB24 -s1024x768 --file=frame-rgb24-1024x768-#.bin /dev/$VIDEO