media: videodev2.h: Add request_fd field to v4l2_buffer

When queuing buffers allow for passing the request that should
be associated with this buffer.

If V4L2_BUF_FLAG_REQUEST_FD is set, then request_fd is used as
the file descriptor.

If a buffer is stored in a request, but not yet queued to the
driver, then V4L2_BUF_FLAG_IN_REQUEST is set.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/usb/cpia2/cpia2_v4l.c

@@ -949,7 +949,7 @@ static int cpia2_dqbuf(struct file *file, void *fh, struct v4l2_buffer *buf)
 	buf->m.offset = cam->buffers[buf->index].data - cam->frame_buffer;
 	buf->length = cam->frame_size;
 	buf->reserved2 = 0;
-	buf->reserved = 0;
+	buf->request_fd = 0;
 	memset(&buf->timecode, 0, sizeof(buf->timecode));
 
 	DBG("DQBUF #%d status:%d seq:%d length:%d\n", buf->index,