Messages in this thread | | | Subject | Re: [PATCH] media: rcar-vin: Move media_device_register to async completion | From | Steve Longerbeam <> | Date | Wed, 17 Jun 2020 11:18:11 -0700 |
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Hi Niklas, Michael,
On 6/17/20 8:28 AM, Niklas Söderlund wrote: > 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@mentor.com> >>>> >>>> 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.
It's been a long time since I looked at this on a Salvator-X. But I do remember there was an OOPS if an attempt was made to enable a link before all devices had bound. Unfortunately I no longer have access to RCAR h/w to prove this point.
>> 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.
I like the idea of allowing a functional pipeline without all devices bound. So I understand the desire to keep media device registration in probe.
So in that case I agree link_notify should be fixed if it still needs fixing to handle non-bound subdevices.
Steve
>> (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@mentor.com> >>>> Signed-off-by: Michael Rodin <mrodin@de.adit-jv.com> >>>> --- >>>> 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
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