On Wed 13 Nov 09:22 PST 2019, Arnaud Pouliquen wrote: > Return the rpmsg buffer MTU for sending message, so rpmsg users > can split a long message in several sub rpmsg buffers. > I won't merge this new api without a client, and I'm still concerned about the details. > Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxx> > --- > V1 to V2 > > V1 patch:https://lore.kernel.org/patchwork/patch/1124684/ > - Change patch title, > - as not solution today to support MTU on GLINK make ops optional, > RPMsg client API returns -ENOTSUPP in this case, > - suppress smd and glink patches. That's ok. > --- > 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. Is the expectation that a call to rpmsg_send() with this size will eventually succeed? > + */ [..] > +static ssize_t virtio_rpmsg_get_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); I'm still under the impression that the rpmsg protocol doesn't have to operate on fixed size messages. Would this then return vrp->num_bufs * vrp->buf_size / 2 - sizeof(rpmsg_hdr)? > +} > + Regards, Bjorn
