Hi Bjorn On 1/13/20 6:24 PM, Bjorn Andersson wrote: > 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. The client exists: it is the rpmsg tty that i 've been rying to upstream since for a while. https://patchwork.kernel.org/cover/11130213/ This patch is the result of some comments you did on rpmsg tty thread. Suman was also interested in and request to merge it independently (https://lkml.org/lkml/2019/9/3/774). That's why i'm trying to do it in 2 steps. > >> 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? yes, this should be the role of the transport layer (e.g. RPMsg VirtIO bus) to ensure this. > >> + */ > [..] >> +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)? it depends on the transport layer. For RPMsg over virtio, this is the size of the payload of a buffer so vrp->buf_size - sizeof(rpmsg_hdr) Regards, Arnaud > >> +} >> + > > Regards, > Bjorn >
