The vc4 planes are setup in hardware by creating a hardware descriptor in a dedicated RAM. As part of the process to setup a plane in KMS, we thus need to allocate some part of that dedicated RAM to store our descriptor there. The async update path will just reuse the descriptor already allocated for that plane and will modify it directly in RAM to match whatever has been asked for. In order to do that, it will compare the descriptor for the old plane state and the new plane state, will make sure they fit in the same size, and check that only the position or buffer address have changed. Reviewed-by: Melissa Wen <mwen@igalia.com> Signed-off-by: Maxime Ripard <maxime@cerno.tech> Link: https://lore.kernel.org/r/20220610115149.964394-2-maxime@cerno.tech
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.
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