Re: [PATCH v8 53/55] [media] v4l2-core: create MC interfaces for devnodes

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On 09/06/2015 02:03 PM, Mauro Carvalho Chehab wrote:
> V4L2 device (and subdevice) nodes should create an interface, if the
> Media Controller support is enabled.
> 
> Please notice that radio devices should not create an entity, as radio
> input/output is either via wires or via ALSA.
> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxx>
> 
> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
> index 44b330589787..07123dd569c4 100644
> --- a/drivers/media/v4l2-core/v4l2-dev.c
> +++ b/drivers/media/v4l2-core/v4l2-dev.c
> @@ -194,9 +194,12 @@ static void v4l2_device_release(struct device *cd)
>  	mutex_unlock(&videodev_lock);
>  
>  #if defined(CONFIG_MEDIA_CONTROLLER)
> -	if (v4l2_dev->mdev &&
> -	    vdev->vfl_type != VFL_TYPE_SUBDEV)
> -		media_device_unregister_entity(&vdev->entity);
> +	if (v4l2_dev->mdev) {
> +		/* Remove interfaces and interface links */
> +		media_devnode_remove(vdev->intf_devnode);
> +		if (vdev->entity.type != MEDIA_ENT_T_UNKNOWN)
> +			media_device_unregister_entity(&vdev->entity);
> +	}
>  #endif
>  
>  	/* Do not call v4l2_device_put if there is no release callback set.
> @@ -713,6 +716,92 @@ static void determine_valid_ioctls(struct video_device *vdev)
>  			BASE_VIDIOC_PRIVATE);
>  }
>  
> +
> +static int video_register_media_controller(struct video_device *vdev, int type)
> +{
> +#if defined(CONFIG_MEDIA_CONTROLLER)
> +	u32 intf_type;
> +	int ret;
> +
> +	if (!vdev->v4l2_dev->mdev)
> +		return 0;
> +
> +	vdev->entity.type = MEDIA_ENT_T_UNKNOWN;
> +
> +	switch (type) {
> +	case VFL_TYPE_GRABBER:
> +		intf_type = MEDIA_INTF_T_V4L_VIDEO;
> +		vdev->entity.type = MEDIA_ENT_T_V4L2_VIDEO;
> +		break;
> +	case VFL_TYPE_VBI:
> +		intf_type = MEDIA_INTF_T_V4L_VBI;
> +		vdev->entity.type = MEDIA_ENT_T_V4L2_VBI;
> +		break;
> +	case VFL_TYPE_SDR:
> +		intf_type = MEDIA_INTF_T_V4L_SWRADIO;
> +		vdev->entity.type = MEDIA_ENT_T_V4L2_SWRADIO;
> +		break;
> +	case VFL_TYPE_RADIO:
> +		intf_type = MEDIA_INTF_T_V4L_RADIO;
> +		/*
> +		 * Radio doesn't have an entity at the V4L2 side to represent
> +		 * radio input or output. Instead, the audio input/output goes
> +		 * via either physical wires or ALSA.
> +		 */
> +		break;
> +	case VFL_TYPE_SUBDEV:
> +		intf_type = MEDIA_INTF_T_V4L_SUBDEV;
> +		/* Entity will be created via v4l2_device_register_subdev() */
> +		break;
> +	default:
> +		return 0;
> +	}
> +
> +	if (vdev->entity.type != MEDIA_ENT_T_UNKNOWN) {
> +		vdev->entity.name = vdev->name;
> +
> +		/* Needed just for backward compatibility with legacy MC API */
> +		vdev->entity.info.dev.major = VIDEO_MAJOR;
> +		vdev->entity.info.dev.minor = vdev->minor;
> +
> +		ret = media_device_register_entity(vdev->v4l2_dev->mdev,
> +						   &vdev->entity);
> +		if (ret < 0) {
> +			printk(KERN_WARNING
> +				"%s: media_device_register_entity failed\n",
> +				__func__);
> +			return ret;
> +		}
> +	}
> +
> +	vdev->intf_devnode = media_devnode_create(vdev->v4l2_dev->mdev,
> +						  intf_type,
> +						  0, VIDEO_MAJOR,
> +						  vdev->minor,
> +						  GFP_KERNEL);
> +	if (!vdev->intf_devnode) {
> +		media_device_unregister_entity(&vdev->entity);
> +		return -ENOMEM;
> +	}
> +
> +	if (vdev->entity.type != MEDIA_ENT_T_UNKNOWN) {
> +		struct media_link *link;
> +
> +		link = media_create_intf_link(&vdev->entity,
> +					      &vdev->intf_devnode->intf, 0);
> +		if (!link) {
> +			media_devnode_remove(vdev->intf_devnode);
> +			media_device_unregister_entity(&vdev->entity);
> +			return -ENOMEM;
> +		}
> +	}
> +
> +	/* FIXME: how to create the other interface links? */
> +
> +#endif
> +	return 0;
> +}
> +
>  /**
>   *	__video_register_device - register video4linux devices
>   *	@vdev: video device structure we want to register
> @@ -908,22 +997,9 @@ int __video_register_device(struct video_device *vdev, int type, int nr,
>  	/* Increase v4l2_device refcount */
>  	v4l2_device_get(vdev->v4l2_dev);
>  
> -#if defined(CONFIG_MEDIA_CONTROLLER)
>  	/* Part 5: Register the entity. */
> -	if (vdev->v4l2_dev->mdev &&
> -	    vdev->vfl_type != VFL_TYPE_SUBDEV) {
> -		vdev->entity.type = MEDIA_ENT_T_V4L2_VIDEO;
> -		vdev->entity.name = vdev->name;
> -		vdev->entity.info.dev.major = VIDEO_MAJOR;
> -		vdev->entity.info.dev.minor = vdev->minor;
> -		ret = media_device_register_entity(vdev->v4l2_dev->mdev,
> -			&vdev->entity);
> -		if (ret < 0)
> -			printk(KERN_WARNING
> -			       "%s: media_device_register_entity failed\n",
> -			       __func__);
> -	}
> -#endif
> +	ret = video_register_media_controller(vdev, type);
> +

This is weird. The 'ret' value is ignored. This was also the case in the original
code, but I don't see why it is ignored. I think that if this fails, then an error
should be returned. Otherwise you'll have an incomplete media graph.

Regards,

	Hans

>  	/* Part 6: Activate this minor. The char device can now be used. */
>  	set_bit(V4L2_FL_REGISTERED, &vdev->flags);
>  
> diff --git a/drivers/media/v4l2-core/v4l2-device.c b/drivers/media/v4l2-core/v4l2-device.c
> index 5b0a30b9252b..e788a085ba96 100644
> --- a/drivers/media/v4l2-core/v4l2-device.c
> +++ b/drivers/media/v4l2-core/v4l2-device.c
> @@ -249,6 +249,17 @@ int v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev)
>  #if defined(CONFIG_MEDIA_CONTROLLER)
>  		sd->entity.info.dev.major = VIDEO_MAJOR;
>  		sd->entity.info.dev.minor = vdev->minor;
> +
> +		/* Interface is created by __video_register_device() */
> +		if (vdev->v4l2_dev->mdev) {
> +			struct media_link *link;
> +
> +			link = media_create_intf_link(&sd->entity,
> +						      &vdev->intf_devnode->intf,
> +						      0);
> +			if (!link)
> +				goto clean_up;
> +		}
>  #endif
>  		sd->devnode = vdev;
>  	}
> @@ -285,7 +296,10 @@ void v4l2_device_unregister_subdev(struct v4l2_subdev *sd)
>  
>  #if defined(CONFIG_MEDIA_CONTROLLER)
>  	if (v4l2_dev->mdev) {
> -		media_entity_remove_links(&sd->entity);
> +		/*
> +		 * No need to explicitly remove links, as both pads and
> +		 * links are removed by the function below, in the right order
> +		 */
>  		media_device_unregister_entity(&sd->entity);
>  	}
>  #endif
> diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
> index acbcd2f5fe7f..eeabf20e87a6 100644
> --- a/include/media/v4l2-dev.h
> +++ b/include/media/v4l2-dev.h
> @@ -86,6 +86,7 @@ struct video_device
>  {
>  #if defined(CONFIG_MEDIA_CONTROLLER)
>  	struct media_entity entity;
> +	struct media_intf_devnode *intf_devnode;
>  #endif
>  	/* device ops */
>  	const struct v4l2_file_operations *fops;
> 

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