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Date:   Wed, 17 Jun 2020 12:56:46 +0200
From:   Niklas =?iso-8859-1?Q?S=F6derlund?= 
        <niklas.soderlund@ragnatech.se>
To:     Michael Rodin <mrodin@de.adit-jv.com>
Cc:     Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-media@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
        linux-kernel@vger.kernel.org, michael@rodin.online,
        efriedrich@de.adit-jv.com, erosca@de.adit-jv.com,
        Steve Longerbeam <steve_longerbeam@mentor.com>
Subject: Re: [PATCH] media: rcar-vin: Move media_device_register to async
 completion
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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.

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.

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 S?derlund