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    SubjectRe: [RFCv4,19/21] media: vim2m: add request support
    On Wed, Mar 14, 2018 at 10:25 PM, Paul Kocialkowski
    <paul.kocialkowski@bootlin.com> wrote:
    > Hi,
    >
    > On Tue, 2018-03-13 at 19:24 +0900, Alexandre Courbot wrote:
    >> On Fri, Mar 9, 2018 at 11:35 PM, Paul Kocialkowski
    >> <paul.kocialkowski@bootlin.com> wrote:
    >> > Hi,
    >> >
    >> > On Thu, 2018-03-08 at 22:48 +0900, Alexandre Courbot wrote:
    >> > > Hi Paul!
    >> > >
    >> > > Thanks a lot for taking the time to try this! I am also working on
    >> > > getting it to work with an actual driver, but you apparently found
    >> > > rough edges that I missed.
    >> > >
    >> > > On Thu, Mar 8, 2018 at 1:37 AM, Paul Kocialkowski
    >> > > <paul.kocialkowski@bootlin.com> wrote:
    >> > > > On Tue, 2018-02-20 at 13:44 +0900, Alexandre Courbot wrote:
    >
    > [...]
    >
    >> > > > > +static int vim2m_request_submit(struct media_request *req,
    >> > > > > + struct media_request_entity_data
    >> > > > > *_data)
    >> > > > > +{
    >> > > > > + struct v4l2_request_entity_data *data;
    >> > > > > +
    >> > > > > + data = to_v4l2_entity_data(_data);
    >> > > >
    >> > > > We need to call v4l2_m2m_try_schedule here so that m2m
    >> > > > scheduling
    >> > > > can
    >> > > > happen when only 2 buffers were queued and no other action was
    >> > > > taken
    >> > > > from usespace. In that scenario, m2m scheduling currently
    >> > > > doesn't
    >> > > > happen.
    >> > >
    >> > > I don't think I understand the sequence of events that results in
    >> > > v4l2_m2m_try_schedule() not being called. Do you mean something
    >> > > like:
    >> > >
    >> > > *
    >> > > * QBUF on output queue with request set
    >> > > * QBUF on capture queue
    >> > > * SUBMIT_REQUEST
    >> > >
    >> > > ?
    >> > >
    >> > > The call to vb2_request_submit() right after should trigger
    >> > > v4l2_m2m_try_schedule(), since the buffers associated to the
    >> > > request
    >> > > will enter the vb2 queue and be passed to the m2m framework, which
    >> > > will then call v4l2_m2m_try_schedule(). Or maybe you are thinking
    >> > > about a different sequence of events?
    >> >
    >> > This is indeed the sequence of events that I'm seeing, but the
    >> > scheduling call simply did not happen on vb2_request_submit. I
    >> > suppose I will need to investigate some more to find out exactly
    >> > why.
    >> >
    >> > IIRC, the m2m qbuf function is called (and fails to schedule) when
    >> > the
    >> > ioctl happens, not when the task is submitted.
    >> >
    >> > This issue is seen with vim2m as well as the rencently-submitted
    >> > sunxi-
    >> > cedrus driver (with the in-driver calls to v4l2_m2m_try_schedule
    >> > removed, obviously). If needs be, I could provide a standalone test
    >> > program to reproduce it.
    >>
    >> If you have a standalone program that can reproduce this on vim2m,
    >> then I would like to see it indeed, if only to understand what I have
    >> missed.
    >
    > You can find the test file for this use case at:
    > https://gist.github.com/paulkocialkowski/4cfa350e1bbe8e3bf714480bba83ea72

    Thanks, I have been able to see what the issue was. One indeed needs
    to call v4l2_m2m_try_schedule() when the request is queued, since the
    driver qbuf() hook does not do it automatically.

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