2cc1802f62
When using vb2 for video decoding, dequeued capture buffers may still be accessed by the hardware: this is the case when they are used as reference frames for decoding subsequent frames. When the buffer is imported with dma-buf, it needs to be mapped before access. Until now, it was mapped when queuing and unmapped when dequeuing, which doesn't work for access as a reference frames. One way to solve this would be to map the buffer again when it is needed as a reference, but the mapping/unmapping operations can seriously impact performance. As a result, map the buffer once (when it is first needed when queued) and keep it mapped until it is freed. Reviewed-on: https://chromium-review.googlesource.com/334103 [Paul: Updated for mainline and changed commit message] Signed-off-by: Pawel Osciak <posciak@chromium.org> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.