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This change is intended to give to the v4l2 drivers a choice to change the default behavior of the v4l2-core DMA mapping direction from DMA_TO/FROM_DEVICE (depending on the buffer type CAPTURE or OUTPUT) to DMA_BIDIRECTIONAL during queue_init time. Initially the issue with DMA mapping direction has been found in Venus encoder driver where the hardware (firmware side) adds few lines padding on bottom of the image buffer, and the consequence is triggering of IOMMU protection faults. This will help supporting venus encoder (and probably other drivers in the future) which wants to map output type of buffers as read/write. Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org> Acked-by: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Hans Verkuil <hansverk@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.