Re: [PATCH v5 1/2] rpmsg: core: add API to get message length

[Arnaud Pouliquen]

hi Suman

On 8/29/19 12:34 AM, Suman Anna wrote:
> Hi Arnaud,
>
> On 8/28/19 10:19 AM, Arnaud Pouliquen wrote:
> > Return the rpmsg buffer size for sending message, so rpmsg users
> > can split a long message in several sub rpmsg buffers.
>
> Thanks for the patch, I also have a need for the same to be able to
> compute permissible payload size. Minor comments below.

Thanks for your review. i will update it ASAP. Then if you need it and 
ack it, i suppose that we could request Bjorn to integrate it in a first 
step, if the rpmsg tty driver has not a level of quality sufficient to 
be accepted...

Regards
Arnaud
> > Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxx>
> > ---
> > V4 to V5 :
> >    - rename rpmsg_get_buf_payload_size to rpmsg_get_mtu
> >
> >   drivers/rpmsg/rpmsg_core.c       | 21 +++++++++++++++++++++
> >   drivers/rpmsg/rpmsg_internal.h   |  2 ++
> >   drivers/rpmsg/virtio_rpmsg_bus.c | 10 ++++++++++
> >   include/linux/rpmsg.h            | 10 ++++++++++
> >   4 files changed, 43 insertions(+)
> >
> > diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c
> > index 8122807db380..daca2e24fc71 100644
> > --- a/drivers/rpmsg/rpmsg_core.c
> > +++ b/drivers/rpmsg/rpmsg_core.c
> > @@ -283,6 +283,27 @@ int rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src, u32 dst,
> >   }
> >   EXPORT_SYMBOL(rpmsg_trysend_offchannel);
> >   
> > +/**
> > + * rpmsg_get_mtu() - get maximum transmission buffer size for sending message.
> > + * @ept: the rpmsg endpoint
> > + *
> > + * This function returns maximum buffer size available for a single message.
> > + *
> > + * Return: the maximum transmission size on success and an appropriate error
> > + * value on failure.
> > + */
> > +
> > +ssize_t rpmsg_get_mtu(struct rpmsg_endpoint *ept)
> > +{
> > +	if (WARN_ON(!ept))
> > +		return -EINVAL;
> > +	if (!ept->ops->get_buf_mtu)
>
> How about calling the ops just get_mtu or rename the function to follow
> the ops name, like all the others.
>
> > +		return -ENXIO;
>
> Perhaps ENOTSUPP or EOPNOTSUPP.
>
> > +
> > +	return ept->ops->get_buf_mtu(ept);
> > +}
> > +EXPORT_SYMBOL(rpmsg_get_mtu);
> > +
> >   /*
> >    * match an rpmsg channel with a channel info struct.
> >    * this is used to make sure we're not creating rpmsg devices for channels
> > diff --git a/drivers/rpmsg/rpmsg_internal.h b/drivers/rpmsg/rpmsg_internal.h
> > index 0d791c30b7ea..645c402569ac 100644
> > --- a/drivers/rpmsg/rpmsg_internal.h
> > +++ b/drivers/rpmsg/rpmsg_internal.h
> > @@ -46,6 +46,7 @@ struct rpmsg_device_ops {
> >    * @trysend:		see @rpmsg_trysend(), required
> >    * @trysendto:		see @rpmsg_trysendto(), optional
> >    * @trysend_offchannel:	see @rpmsg_trysend_offchannel(), optional
> > + * @get_buf_payload_size: see @rpmsg_get_buf_payload_size(), optional
>
> Missed updating the kerneldoc to the new name.
>
> >    *
> >    * Indirection table for the operations that a rpmsg backend should implement.
> >    * In addition to @destroy_ept, the backend must at least implement @send and
> > @@ -65,6 +66,7 @@ struct rpmsg_endpoint_ops {
> >   			     void *data, int len);
> >   	__poll_t (*poll)(struct rpmsg_endpoint *ept, struct file *filp,
> >   			     poll_table *wait);
> > +	ssize_t (*get_buf_mtu)(struct rpmsg_endpoint *ept);
> >   };
> >   
> >   int rpmsg_register_device(struct rpmsg_device *rpdev);
> > diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
> > index e757f0038a1c..f80b1ad23e7e 100644
> > --- a/drivers/rpmsg/virtio_rpmsg_bus.c
> > +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
> > @@ -178,6 +178,7 @@ static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data,
> >   				  int len, u32 dst);
> >   static int virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src,
> >   					   u32 dst, void *data, int len);
> > +static ssize_t virtio_get_buf_mtu(struct rpmsg_endpoint *ept);
>
> Minor nit, virtio_rpmsg_ prefix similar to all the other ops.
>
> regards
> Suman
>
> >   
> >   static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
> >   	.destroy_ept = virtio_rpmsg_destroy_ept,
> > @@ -187,6 +188,7 @@ static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
> >   	.trysend = virtio_rpmsg_trysend,
> >   	.trysendto = virtio_rpmsg_trysendto,
> >   	.trysend_offchannel = virtio_rpmsg_trysend_offchannel,
> > +	.get_buf_mtu = virtio_get_buf_mtu,
> >   };
> >   
> >   /**
> > @@ -702,6 +704,14 @@ static int virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src,
> >   	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
> >   }
> >   
> > +static ssize_t virtio_get_buf_mtu(struct rpmsg_endpoint *ept)
> > +{
> > +	struct rpmsg_device *rpdev = ept->rpdev;
> > +	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
> > +
> > +	return vch->vrp->buf_size - sizeof(struct rpmsg_hdr);
> > +}
> > +
> >   static int rpmsg_recv_single(struct virtproc_info *vrp, struct device *dev,
> >   			     struct rpmsg_hdr *msg, unsigned int len)
> >   {
> > diff --git a/include/linux/rpmsg.h b/include/linux/rpmsg.h
> > index 9fe156d1c018..9d638bf2bdce 100644
> > --- a/include/linux/rpmsg.h
> > +++ b/include/linux/rpmsg.h
> > @@ -135,6 +135,8 @@ int rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src, u32 dst,
> >   __poll_t rpmsg_poll(struct rpmsg_endpoint *ept, struct file *filp,
> >   			poll_table *wait);
> >   
> > +ssize_t rpmsg_get_mtu(struct rpmsg_endpoint *ept);
> > +
> >   #else
> >   
> >   static inline int register_rpmsg_device(struct rpmsg_device *dev)
> > @@ -242,6 +244,14 @@ static inline __poll_t rpmsg_poll(struct rpmsg_endpoint *ept,
> >   	return 0;
> >   }
> >   
> > +static ssize_t rpmsg_get_mtu(struct rpmsg_endpoint *ept)
> > +{
> > +	/* This shouldn't be possible */
> > +	WARN_ON(1);
> > +
> > +	return -ENXIO;
> > +}
> > +
> >   #endif /* IS_ENABLED(CONFIG_RPMSG) */
> >   
> >   /* use a macro to avoid include chaining to get THIS_MODULE */