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a562d6dc86
vb2_read() and vb2_write() return size_t, but propagate
negative errno values from __vb2_perform_fileio().
This relies on implicit signed/unsigned conversions in callers
(e.g. vb2_fop_read()) to recover error codes:
__vb2_perform_fileio() -> -EINVAL
vb2_read() -> (size_t)-EINVAL
vb2_fop_read() -> -EINVAL
This relies on implicit conversions that are not obvious.
These helpers are exported (EXPORT_SYMBOL_GPL) and part of the
vb2 API, so changing their return type may affect existing users.
However, they conceptually follow read/write semantics, where
ssize_t is typically used to return either a byte count or a
negative error code.
Switch vb2_read() and vb2_write() to ssize_t, and update
__vb2_perform_fileio() accordingly.
Signed-off-by: Zile Xiong <xiongzile99@gmail.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Fixes: b25748fe61 ("[media] v4l: videobuf2: add read() and write() emulator")
Cc: stable@vger.kernel.org
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>