Re: [PATCH 8/9] rpmsg: virtio: use rpmsg_ns driver to manage ns announcement

[Mathieu Poirier]

Hi Arnaud,

On Fri, Jul 31, 2020 at 01:47:31PM +0200, Arnaud Pouliquen wrote:
> Use the new rpmsg_ns API to send the name service announcements if
> the VIRTIO_RPMSG_F_NS is set, else just not implement the ops.
> 
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxx>
> ---
>  drivers/rpmsg/virtio_rpmsg_bus.c | 94 +++++---------------------------
>  1 file changed, 13 insertions(+), 81 deletions(-)
> 
> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
> index f771fdae150e..3c771a6392be 100644
> --- a/drivers/rpmsg/virtio_rpmsg_bus.c
> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
> @@ -91,35 +91,6 @@ struct rpmsg_hdr {
>  	u8 data[];
>  } __packed;
>  
> -/**
> - * struct rpmsg_ns_msg - dynamic name service announcement message
> - * @name: name of remote service that is published
> - * @addr: address of remote service that is published
> - * @flags: indicates whether service is created or destroyed
> - *
> - * This message is sent across to publish a new service, or announce
> - * about its removal. When we receive these messages, an appropriate
> - * rpmsg channel (i.e device) is created/destroyed. In turn, the ->probe()
> - * or ->remove() handler of the appropriate rpmsg driver will be invoked
> - * (if/as-soon-as one is registered).
> - */
> -struct rpmsg_ns_msg {
> -	char name[RPMSG_NAME_SIZE];
> -	__virtio32 addr;
> -	__virtio32 flags;
> -} __packed;
> -
> -/**
> - * enum rpmsg_ns_flags - dynamic name service announcement flags
> - *
> - * @RPMSG_NS_CREATE: a new remote service was just created
> - * @RPMSG_NS_DESTROY: a known remote service was just destroyed
> - */
> -enum rpmsg_ns_flags {
> -	RPMSG_NS_CREATE		= 0,
> -	RPMSG_NS_DESTROY	= 1,
> -};
> -
>  /**
>   * @vrp: the remote processor this channel belongs to
>   */
> @@ -324,60 +295,18 @@ static void virtio_rpmsg_destroy_ept(struct rpmsg_endpoint *ept)
>  	__rpmsg_destroy_ept(vch->vrp, ept);
>  }
>  
> -static int virtio_rpmsg_announce_create(struct rpmsg_device *rpdev)
> -{
> -	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
> -	struct virtproc_info *vrp = vch->vrp;
> -	struct device *dev = &rpdev->dev;
> -	int err = 0;
> -
> -	/* need to tell remote processor's name service about this channel ? */
> -	if (rpdev->announce && rpdev->ept &&
> -	    virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
> -		struct rpmsg_ns_msg nsm;
> -
> -		strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
> -		nsm.addr = cpu_to_virtio32(vrp->vdev, rpdev->ept->addr);
> -		nsm.flags = cpu_to_virtio32(vrp->vdev, RPMSG_NS_CREATE);
> -
> -		err = rpmsg_sendto(rpdev->ept, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
> -		if (err)
> -			dev_err(dev, "failed to announce service %d\n", err);
> -	}
> -
> -	return err;
> -}
> -
> -static int virtio_rpmsg_announce_destroy(struct rpmsg_device *rpdev)
> -{
> -	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
> -	struct virtproc_info *vrp = vch->vrp;
> -	struct device *dev = &rpdev->dev;
> -	int err = 0;
> -
> -	/* tell remote processor's name service we're removing this channel */
> -	if (rpdev->announce && rpdev->ept &&
> -	    virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
> -		struct rpmsg_ns_msg nsm;
> -
> -		strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
> -		nsm.addr = cpu_to_virtio32(vrp->vdev, rpdev->ept->addr);
> -		nsm.flags = cpu_to_virtio32(vrp->vdev, RPMSG_NS_DESTROY);
> -
> -		err = rpmsg_sendto(rpdev->ept, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
> -		if (err)
> -			dev_err(dev, "failed to announce service %d\n", err);
> -	}
> -
> -	return err;
> -}
> -
>  static const struct rpmsg_device_ops virtio_rpmsg_ops = {
>  	.create_channel = virtio_rpmsg_create_channel,
>  	.release_channel = virtio_rpmsg_release_channel,
>  	.create_ept = virtio_rpmsg_create_ept,
> -	.announce_create = virtio_rpmsg_announce_create,
> -	.announce_destroy = virtio_rpmsg_announce_destroy,
> +};
> +
> +static const struct rpmsg_device_ops virtio_rpmsg_w_nsa_ops = {
> +	.create_channel = virtio_rpmsg_create_channel,
> +	.release_channel = virtio_rpmsg_release_channel,
> +	.create_ept = virtio_rpmsg_create_ept,
> +	.announce_create = rpmsg_ns_announce_create,
> +	.announce_destroy = rpmsg_ns_announce_destroy,
>  };
>  
>  static void virtio_rpmsg_release_device(struct device *dev)
> @@ -423,7 +352,10 @@ __rpmsg_create_channel(struct virtproc_info *vrp,
>  	rpdev = &vch->rpdev;
>  	rpdev->src = chinfo->src;
>  	rpdev->dst = chinfo->dst;
> -	rpdev->ops = &virtio_rpmsg_ops;
> +	if (virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS))
> +		rpdev->ops = &virtio_rpmsg_w_nsa_ops;
> +	else
> +		rpdev->ops = &virtio_rpmsg_ops;

Yesterday I struggled with this part and I still do this morning.  Function
__rpmsg_create_channel() can only be called if VIRTIO_RPMSG_F_NS is set so there
is no need to check it again.  I would also have expected this patch to be a
simple replace of the .announce_create/destroy functions.  Adding an ops that
doesn't have the .announce_create/destroy functions looks like a feature to me,
and one that I don't quite get.

Do you think you could expand on the motivation behind this patch?

Thanks,
Mathieu 

>  
>  	/*
>  	 * rpmsg server channels has predefined local address (for now),
> @@ -933,7 +865,7 @@ static int rpmsg_probe(struct virtio_device *vdev)
>  
>  		/* Assign public information to the rpmsg_device */
>  		rpdev_ns = &vch->rpdev;
> -		rpdev_ns->ops = &virtio_rpmsg_ops;
> +		rpdev_ns->ops = &virtio_rpmsg_w_nsa_ops;
>  
>  		rpdev_ns->dev.parent = &vrp->vdev->dev;
>  		rpdev_ns->dev.release = virtio_rpmsg_release_device;
> -- 
> 2.17.1
>