Re: [PATCH v6 1/2] rpmsg: core: add API to get message length

[Arnaud Pouliquen]

Hi Suman

On 9/4/19 6:36 PM, Suman Anna wrote:
> Hi Arnaud,
>
> On 9/4/19 8:09 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.
>
> Couple more minor comments..
>
> > Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxx>
> > ---
> >   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 e330ec4dfc33..a6ef54c4779a 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_mtu)
> > +		return -ENOTSUPP;
> > +
> > +	return ept->ops->get_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 3fc83cd50e98..12b9e72adc75 100644
> > --- a/drivers/rpmsg/rpmsg_internal.h
> > +++ b/drivers/rpmsg/rpmsg_internal.h
> > @@ -47,6 +47,7 @@ struct rpmsg_device_ops {
> >    * @trysendto:		see @rpmsg_trysendto(), optional
> >    * @trysend_offchannel:	see @rpmsg_trysend_offchannel(), optional
> >    * @poll:		see @rpmsg_poll(), optional
> > + * @get_mtu:		see @get_mpu(), required
>
> see @rpmsg_get_mtu(). Isn't this optional atm, since we haven't added
> the callback for SMD transport?

It is a good point.
On one side, if optional, rpmsg_get_mtu returns an error and the rpmsg 
client has to define a default value, but which one?
On the other, if required, i need to implement it for SMD and Glink 
driver. Calculate the mtu for these implementations does not seems 
trivial (if possible...). And i don't know how to test dev on these 
platforms.

Any suggestions?

Regards
Arnaud

> >    *
> >    * Indirection table for the operations that a rpmsg backend should implement.
> >    * In addition to @destroy_ept, the backend must at least implement @send and
> > @@ -66,6 +67,7 @@ struct rpmsg_endpoint_ops {
> >   			     void *data, int len);
> >   	__poll_t (*poll)(struct rpmsg_endpoint *ept, struct file *filp,
> >   			     poll_table *wait);
> > +	ssize_t (*get_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 376ebbf880d6..fab01b67a550 100644
> > --- a/drivers/rpmsg/virtio_rpmsg_bus.c
> > +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
> > @@ -175,6 +175,7 @@ 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_rpmsg_get_buf_mtu(struct rpmsg_endpoint *ept);
> >   
> >   static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
> >   	.destroy_ept = virtio_rpmsg_destroy_ept,
> > @@ -184,6 +185,7 @@ static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
> >   	.trysend = virtio_rpmsg_trysend,
> >   	.trysendto = virtio_rpmsg_trysendto,
> >   	.trysend_offchannel = virtio_rpmsg_trysend_offchannel,
> > +	.get_mtu = virtio_rpmsg_get_buf_mtu,
> >   };
> >   
> >   /**
> > @@ -699,6 +701,14 @@ 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_rpmsg_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)
>
> static inline
>
> regards
> Suman
>
> > +{
> > +	/* 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 */