Hi Michael,
On 2020-06-17 17:15:37 +0200, Michael Rodin wrote:
> Hi Niklas and Steve,
>
> On Wed, Jun 17, 2020 at 12:56:46PM +0200, Niklas Söderlund wrote:
> > Hi Michael and Steve,
> >
> > On 2020-06-16 19:31:36 +0200, Michael Rodin wrote:
> > > From: Steve Longerbeam <steve_longerbeam@xxxxxxxxxx>
> > >
> > > The media_device is registered during driver probe, before async
> > > completion, so it is possible for .link_notify to be called before
> > > all devices are bound.
> > >
> > > Fix this by moving media_device_register() to rvin_group_notify_complete().
> > > This ensures that all devices are now bound (the rcar-csi2 subdevices and
> > > and video capture devices) before .link_notify can be called.
> >
> > I'm curious to what situation created the need for this change. I'm
> > currently trying to take the VIN driver in the opposite direction [1]
> > with the end goal of registering video devices at probe time and then
> > allow the media graph to populate as devices becomes available.
>
> It looks like almost all platform drivers call media_device_register() in
> the completion callback. From my understaning it is necessary to ensure
> that all subdevices are bound and all links are created before the user
> can enable any link (which would trigger link_notify callback execution)
> and set formats. If I am not mistaken, Steve could observe an "OOPS" or
> at least it is theoretically possible.
If an OOPS have been observed I would be interested to see it. That way
we can fix the OOPS and keep the media graph registration where it is
today.
>
> Actually I found that this patch alone is not enough even if it is correct,
> because we also have to register the media device in rvin_parallel_notify_complete()
> in case if there is only a parallel video input device attached.
>
> > My reason for this is that we could have a functional pipeline inside
> > the graph even if it's not complete. This came out of the GMSL work done
> > a while pack where I had a faulty camera that would prevent the other 7
> > in the system to function.
>
> I agree that if a probe of a faulty subdevice fails, this should not affect
> functionality of the other attached subdevices. The "complete" callback of
> the async notifier is probably not executed in this case, so I guess, we
> would have to register the media device in the "bound" callback after the first
> subdevice has been probed? Otherwise there is not much sense to have video
> capture devices, which are not connected to any source.
Calling it in the bound callback is mostly the same as it is today, as
link_notify could then be called when not all entities are in the graph.
In fact even if we where tp move the media device registration to the t
complete callback we have this problem if any of the subdevices are
unbound. Then we are back to the state with a registerd media device
where not all entities are present.
I think the solution here is to address the issue (if any) in the
link_notify callback when the graph is not fully populated.
>
> (Delayed) population of the media graph after media device registration
> sounds also like a requirement for device tree overlay support, which would
> also be a nice feature.
>
> > 1. [PATCH 0/5] media-device: Report if graph is complete
> >
> > >
> > > Signed-off-by: Steve Longerbeam <steve_longerbeam@xxxxxxxxxx>
> > > Signed-off-by: Michael Rodin <mrodin@xxxxxxxxxxxxxx>
> > > ---
> > > drivers/media/platform/rcar-vin/rcar-core.c | 14 ++++++--------
> > > 1 file changed, 6 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/drivers/media/platform/rcar-vin/rcar-core.c b/drivers/media/platform/rcar-vin/rcar-core.c
> > > index 7440c89..e70f83b 100644
> > > --- a/drivers/media/platform/rcar-vin/rcar-core.c
> > > +++ b/drivers/media/platform/rcar-vin/rcar-core.c
> > > @@ -253,7 +253,6 @@ static int rvin_group_init(struct rvin_group *group, struct rvin_dev *vin)
> > > struct media_device *mdev = &group->mdev;
> > > const struct of_device_id *match;
> > > struct device_node *np;
> > > - int ret;
> > >
> > > mutex_init(&group->lock);
> > >
> > > @@ -266,7 +265,6 @@ static int rvin_group_init(struct rvin_group *group, struct rvin_dev *vin)
> > > vin_dbg(vin, "found %u enabled VIN's in DT", group->count);
> > >
> > > mdev->dev = vin->dev;
> > > - mdev->ops = &rvin_media_ops;
> > >
> > > match = of_match_node(vin->dev->driver->of_match_table,
> > > vin->dev->of_node);
> > > @@ -278,11 +276,7 @@ static int rvin_group_init(struct rvin_group *group, struct rvin_dev *vin)
> > >
> > > media_device_init(mdev);
> > >
> > > - ret = media_device_register(&group->mdev);
> > > - if (ret)
> > > - rvin_group_cleanup(group);
> > > -
> > > - return ret;
> > > + return 0;
> > > }
> > >
> > > static void rvin_group_release(struct kref *kref)
> > > @@ -688,6 +682,8 @@ static int rvin_group_notify_complete(struct v4l2_async_notifier *notifier)
> > > return ret;
> > > }
> > >
> > > + vin->group->mdev.ops = &rvin_media_ops;
> > > +
> > > /* Register all video nodes for the group. */
> > > for (i = 0; i < RCAR_VIN_NUM; i++) {
> > > if (vin->group->vin[i] &&
> > > @@ -736,8 +732,10 @@ static int rvin_group_notify_complete(struct v4l2_async_notifier *notifier)
> > > }
> > > }
> > > mutex_unlock(&vin->group->lock);
> > > + if (ret)
> > > + return ret;
> > >
> > > - return ret;
> > > + return media_device_register(&vin->group->mdev);
> > > }
> > >
> > > static void rvin_group_notify_unbind(struct v4l2_async_notifier *notifier,
> > > --
> > > 2.7.4
> > >
> >
> > --
> > Regards,
> > Niklas Söderlund
>
> --
> Best Regards,
> Michael
--
Regards,
Niklas Söderlund
