When user space stops streaming, there may be buffers which have been given
to buf_prepare() and which may or may not have been passed to buf_queue().
The videobuf2 core simply takes those buffers back; if buf_prepare() does
work that needs cleaning up (like setting up a DMA mapping), that cleanup
will not happen.

This patch establishes a simple contract with drivers: buffers given to
buf_prepare() will eventually see a buf_finish() call.

Signed-off-by: Jonathan Corbet <cor...@lwn.net>
---
 drivers/media/video/videobuf2-core.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/drivers/media/video/videobuf2-core.c 
b/drivers/media/video/videobuf2-core.c
index 6ba1461..2ba08ab 100644
--- a/drivers/media/video/videobuf2-core.c
+++ b/drivers/media/video/videobuf2-core.c
@@ -1177,6 +1177,7 @@ EXPORT_SYMBOL_GPL(vb2_streamon);
  */
 static void __vb2_queue_cancel(struct vb2_queue *q)
 {
+       struct vb2_buffer *vb;
        unsigned int i;
 
        /*
@@ -1188,13 +1189,18 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
        q->streaming = 0;
 
        /*
-        * Remove all buffers from videobuf's list...
+        * Remove all buffers from videobuf's list...  Give the driver
+        * a chance to clean them up first, though.
         */
+       list_for_each_entry(vb, &q->queued_list, queued_entry)
+               call_qop(q, buf_finish, vb);
        INIT_LIST_HEAD(&q->queued_list);
        /*
         * ...and done list; userspace will not receive any buffers it
         * has not already dequeued before initiating cancel.
         */
+       list_for_each_entry(vb, &q->done_list, done_entry)
+               call_qop(q, buf_finish, vb);
        INIT_LIST_HEAD(&q->done_list);
        wake_up_all(&q->done_wq);
 
-- 
1.7.6

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