Re: [PATCH 6/7] [media] gspca: fix a v4l2-compliance failure during VIDIOC_REQBUFS

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Hi,

On 09-03-16 17:03, Antonio Ospite wrote:
When calling VIDIOC_REQBUFS v4l2-compliance fails with this message:

   fail: v4l2-test-buffers.cpp(476): q.reqbufs(node, 1)
   test VIDIOC_REQBUFS/CREATE_BUFS/QUERYBUF: FAIL

By looking at the v4l2-compliance code the failure happens when trying
to request V4L2_MEMORY_USERPTR buffers without freeing explicitly the
previously allocated V4L2_MEMORY_MMAP buffers.

This would suggest that when changing the memory field in struct
v4l2_requestbuffers the driver is supposed to free automatically any
previous allocated buffers, and looking for inspiration at the code in
drivers/media/v4l2-core/videobuf2-core.c::vb2_core_reqbufs() seems to
confirm this interpretation; however gspca is just returning -EBUSY in
this case.

Removing the special handling for the case of a different memory value
fixes the compliance failure.

Signed-off-by: Antonio Ospite <ao2@xxxxxx>
---

This should be safe, but I'd really like a comment from someone with a more
global knowledge of v4l2.

If my interpretation about how drivers should behave when the value of the
memory field changes is correct, I could send also a documentation update for
Documentation/DocBook/media/v4l/vidioc-reqbufs.xml

Just let me know.

Thanks,
    Antonio


  drivers/media/usb/gspca/gspca.c | 7 -------
  1 file changed, 7 deletions(-)

diff --git a/drivers/media/usb/gspca/gspca.c b/drivers/media/usb/gspca/gspca.c
index 84b0d6a..915b6c7 100644
--- a/drivers/media/usb/gspca/gspca.c
+++ b/drivers/media/usb/gspca/gspca.c
@@ -1402,13 +1402,6 @@ static int vidioc_reqbufs(struct file *file, void *priv,
  	if (mutex_lock_interruptible(&gspca_dev->queue_lock))
  		return -ERESTARTSYS;

-	if (gspca_dev->memory != GSPCA_MEMORY_NO
-	    && gspca_dev->memory != GSPCA_MEMORY_READ
-	    && gspca_dev->memory != rb->memory) {
-		ret = -EBUSY;
-		goto out;
-	}
-

reqbufs is used internally and this change will allow changing
gspca_dev->memory from USERPTR / MMAP to GSPCA_MEMORY_READ
please replace this check with a check to only allow
rb->memory to be GSPCA_MEMORY_READ when coming from GSPCA_MEMORY_NO
or GSPCA_MEMORY_READ

Regards,

Hans

  	/* only one file may do the capture */
  	if (gspca_dev->capt_file != NULL
  	    && gspca_dev->capt_file != file) {

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