[media] vb2: push the mmap semaphore down to __buf_prepare()

Rather than taking the mmap semaphore at a relatively high-level function,
push it down to the place where it is really needed.

It was placed in vb2_queue_or_prepare_buf() to prevent racing with other
vb2 calls. The only way I can see that a race can happen is when two
threads queue the same buffer. The solution for that it to introduce
a PREPARING state.

Moving it down offers opportunities to simplify the code.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 0ae974ee8894..ea766525a268 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -142,6 +142,7 @@ enum vb2_fileio_flags {
 /**
  * enum vb2_buffer_state - current video buffer state
  * @VB2_BUF_STATE_DEQUEUED:     buffer under userspace control
+ * @VB2_BUF_STATE_PREPARING:    buffer is being prepared in videobuf
  * @VB2_BUF_STATE_PREPARED:     buffer prepared in videobuf and by the driver
  * @VB2_BUF_STATE_QUEUED:       buffer queued in videobuf, but not in driver
  * @VB2_BUF_STATE_ACTIVE:       buffer queued in driver and possibly used
@@ -154,6 +155,7 @@ enum vb2_fileio_flags {
  */
 enum vb2_buffer_state {
         VB2_BUF_STATE_DEQUEUED,
+        VB2_BUF_STATE_PREPARING,
         VB2_BUF_STATE_PREPARED,
         VB2_BUF_STATE_QUEUED,
         VB2_BUF_STATE_ACTIVE,