[PATCH for v4.20 0/5] vb2 fixes (mostly request API related)

[hverkuil-cisco@xs4all.nl]

From: Hans Verkuil <hverkuil-cisco@xs4all.nl>

While improving the v4l2-compliance tests I came across several vb2
problems.

After modifying v4l2-compliance I was now able to use the vivid error
injection feature to test what happens if VIDIOC_STREAMON fails and
a following STREAMON succeeds.

This generated patches 1/5 and 4/5+5/5.

Patch 1/5 fixes an issue that was never noticed before since it didn't
result in kernel oopses or warnings, but after the second STREAMON it
won't call start_streaming anymore until you call REQBUFS(0) or close
the device node.

Patches 4 and 5 are request specific fixes for the same corner case:
the code would unbind (in vb2) or complete (in vivid) a request if
start_streaming fails, but it should just leave things as-is. The
buffer is just put back in the queue, ready for the next attempt at
STREAMON.

Patch 2/5 was also discovered by v4l2-compliance: the request fd in
v4l2_buffer should be ignored by VIDIOC_PREPARE_BUF, but it wasn't.

Patch 3/5 fixes a nasty corner case: a buffer with associated request
is queued, and then the request fd is closed by v4l2-compliance.

When the driver calls vb2_buffer_done, the buffer request object is
unbound, the object is put, and indirectly the associated request
is put as well, and since that was the last references to the request
the whole request is released, which requires the ability to call
mutex_lock. But vb2_buffer_done is atomic (it can be called
from interrupt context), so this shouldn't happen.

vb2 now takes an extra refcount to the request on qbuf and releases
it on dqbuf and at two other places where an internal dqbuf is done.

Note that 'skip request checks for VIDIOC_PREPARE_BUF' is a duplicate
of https://patchwork.linuxtv.org/patch/53171/, which is now marked as
superseded.

I've marked all these patches for 4.20, but I think it is also possible
to apply them for 4.21 since the request API is only used by virtual
drivers and a staging driver.

Regards,

	Hans

Hans Verkuil (5):
  vb2: don't call __vb2_queue_cancel if vb2_start_streaming failed
  vb2: skip request checks for VIDIOC_PREPARE_BUF
  vb2: keep a reference to the request until dqbuf
  vb2: don't unbind/put the object when going to state QUEUED
  vivid: drop v4l2_ctrl_request_complete() from start_streaming

 .../media/common/videobuf2/videobuf2-core.c   | 44 +++++++++++++++----
 .../media/common/videobuf2/videobuf2-v4l2.c   | 11 +++--
 drivers/media/platform/vivid/vivid-sdr-cap.c  |  2 -
 drivers/media/platform/vivid/vivid-vbi-cap.c  |  2 -
 drivers/media/platform/vivid/vivid-vbi-out.c  |  2 -
 drivers/media/platform/vivid/vivid-vid-cap.c  |  2 -
 drivers/media/platform/vivid/vivid-vid-out.c  |  2 -
 include/media/videobuf2-core.h                |  2 +
 8 files changed, 44 insertions(+), 23 deletions(-)

-- 
2.19.1