Hi, On 6/14/23 17:24, Bjorn Andersson wrote: > On Mon, Apr 24, 2023 at 02:49:29PM +0200, Arnaud POULIQUEN wrote: >> Hello, >> >> On 4/22/23 12:42, Sarannya S wrote: >>> From: Deepak Kumar Singh <quic_deesin@xxxxxxxxxxx> >>> >>> Some transports like Glink support the state notifications between >>> clients using flow control signals similar to serial protocol signals. >>> Local glink client drivers can send and receive flow control status >>> to glink clients running on remote processors. >>> >>> Add APIs to support sending and receiving of flow control status by >>> rpmsg clients. >>> >>> Signed-off-by: Deepak Kumar Singh <quic_deesin@xxxxxxxxxxx> >>> Signed-off-by: Sarannya S <quic_sarannya@xxxxxxxxxxx> >>> --- >>> drivers/rpmsg/rpmsg_core.c | 21 +++++++++++++++++++++ >>> drivers/rpmsg/rpmsg_internal.h | 2 ++ >>> include/linux/rpmsg.h | 15 +++++++++++++++ >>> 3 files changed, 38 insertions(+) >>> >>> diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c >>> index a2207c0..e8bbe05 100644 >>> --- a/drivers/rpmsg/rpmsg_core.c >>> +++ b/drivers/rpmsg/rpmsg_core.c >>> @@ -331,6 +331,25 @@ int rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src, u32 dst, >>> EXPORT_SYMBOL(rpmsg_trysend_offchannel); >>> >>> /** >>> + * rpmsg_set_flow_control() - sets/clears serial flow control signals >>> + * @ept: the rpmsg endpoint >>> + * @enable: pause/resume incoming data flow >>> + * @dst: destination address of the endpoint >>> + * >>> + * Return: 0 on success and an appropriate error value on failure. >>> + */ >>> +int rpmsg_set_flow_control(struct rpmsg_endpoint *ept, bool enable, u32 dst) >>> +{ >>> + if (WARN_ON(!ept)) >>> + return -EINVAL; >>> + if (!ept->ops->set_flow_control) >>> + return -ENXIO; >> >> Here we return an error if the backend does not implement the ops. >> But the set_flow_control ops is optional. >> Should we return 0 instead with a debug message? >> > > It seems reasonable to allow the software to react to the absence of > flow control support, so a debug message wouldn't help. > > But advertising that more explicitly by returning something like > EOPNOTSUPP seems better. Right, this seems more reliable. Thanks, Arnaud > > Regards, > Bjorn