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[ Upstream commit a9d4ef6434 ]
When doing dma_alloc_coherent in the driver, we add a certain hard-coded
offset to the DMA address before returning to the callee function. This
offset is needed when our device use this DMA address to perform
outbound transactions to the host.
However, if we want to map the DMA'able memory to the user via
dma_mmap_coherent(), we need to pass the original dma address, without
this offset. Otherwise, we will get erronouos mapping.
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Sasha Levin <sashal@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.