media: add virtio-media driver
Add the first version of the virtio-media driver.
This driver acts roughly as a V4L2 relay between user-space and the
virtio virtual device on the host, so it is relatively simple, yet
unconventional. It doesn't use VB2 or other frameworks typically used in
a V4L2 driver, and most of its complexity resides in correctly and
efficiently building the virtio descriptor chain to pass to the host,
avoiding copies whenever possible. This is done by
scatterlist_builder.[ch].
virtio_media_ioctls.c proxies each supported ioctl to the host, using
code generated through macros for ioctls that can be forwarded directly,
which is most of them.
virtio_media_driver.c provides the expected driver hooks, and support
for mmapping and polling.
This version supports MMAP buffers, while USERPTR buffers can also be
enabled through a driver option. DMABUF support is still pending.
Signed-off-by: Alexandre Courbot <acourbot@google.com>
Signed-off-by: Alexandre Courbot <gnurou@gmail.com>
Message-Id: <20250412-virtio-media-v3-1-97dc94c18398@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
12 files changed
