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The RGA driver allocates two buffers for the DMA descriptors of the input and output buffers. Whenever a new job is processed, the descriptor list is updated for the current buffers. By updating the descriptor list during buf_prepare, it is possible to correctly fail DMABUF imports if the buffers that shall be imported are not within the 32 bit address range that can be addressed by the RGA. Managing the DMA descriptor list with the buffer also makes it easier to track the buffer mapping and the plane offsets into this mapping. The cost is that the driver now requires DMA coherent memory per buffer for the descriptor list. However, the size scales with the size of the video buffers and is not allocated if the RGA is not used. While at it, use dma_alloc_coherent to allocate the descriptors and get rid of the virt_to_phys calls to get the physical addresses. Signed-off-by: Michael Tretter <m.tretter@pengutronix.de> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
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.