This week’s progress in our VPU driver development effort was focused on two main tasks: submitting the sixth revision of the Cedrus VPU driver series to the mainline Linux kernel and starting the work on H265 decoding.
The patch series for this new iteration of the driver was submitted on Wednesday and contains both functional and cosmetic changes. Most notably, we implemented support for video-specific quantization matrices in MPEG2, one of the final extension bits we were missing until then, but also cleaned up the register definitions for the driver. At this point, there are no undocumented registers or fields left, which makes the overall understanding of the hardware interactions much more straightforward. The driver was also moved to staging drivers, not because it was deemed of poor quality but rather because V4L2 maintainers want to keep the ability to change the controls that our driver is using even after it is merged.
Aside of this work, we started looking into H265 decoding, that was also already implemented in libvdpau-sunxi for the downstream modified version of the Linux kernel provided by Allwinner for the H3 (still based on Linux 3.4 to this day, which was released in 2012). After setting up a board with this kernel and libvdpau-sunxi, we were able to dump the register access made by libvdpau-sunxi, providing a reference for bringing up H265 support in the Cedrus VPU driver!
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The driver moved to stage drivers, not because it was deemed of poor quality but rather because V4L2 maintainers want to keep the ability to change the controls that our driver is using even after it is merged.