On Tue 09 Oct 09:02 PDT 2018, Arnaud Pouliquen wrote: > hello Bjorn, > > On 10/08/2018 06:23 PM, Bjorn Andersson wrote: > > On Mon 08 Oct 06:08 PDT 2018, Arnaud Pouliquen wrote: > > > >> Hi Arun, Bjorn, > >> > >> On 10/08/2018 08:38 AM, Arun Kumar Neelakantam wrote: > >>> Glink transport support signals to exchange state notification between > >>> local and remote side clients. Adding support to send/receive the signal > >>> command and notify the clients through callback and POLL notification. > >> > >> Please correct me if i'm wrong...My concern here is that this patchset > >> implements a rpmsg service in the rpmsg core. I would separate this from > >> the rpmsg core, as this is not part of the rpmsg protocol but seems > >> linked to the serial protocol itself. > >> Could it be implemented in rpmsg_char, using a dedicated channel...? > >> > > > > rpmsg_char does expose a rpmsg channel (be it virtio, smd or glink) to > > user space. This patch series add support for invoking TIOCMGET and > > TIOCMSET on these channels. > > I'm not familiar with this concept, that could explain that i don't > understand this patchset... > > TIOCMGET and TIOCMSET is related to the serial/console flow control, to > control remote modem/processor, right? > Correct, using the known tty ioctls for flow control we allow userspace to communicate flow control information to the rpmsg_char driver. > it seems be implemented only to support the rpmsg_char ioctl interface. > When i have a look to the glink code, signal is treated by a message > sent to remote processor. Therefore it seems that it could be treated as > a service on top of rpmsg (so treat it in rpmsg_char instead of extend > the rpmsg protocol to treat it in glink driver). > The glink message is a control message, so it's not possible to pass this inside a channel. As such it's not possible to solve this entirely in rpmsg_char. Looking at SMD, this is a set of bits in a per-channel control structure. So there it's clearer that it's some side-band control information. Further more, the rpmsg_char driver just exposes a channel to user space, it does not care about the data inside. As such it's not possible to generically extend it to support this with in-band messages. > > > > In addition to adding the client side of this to rpmsg_char it provides > > this support for glink, but the same mechanism exists in smd - while > > this is not supported (today) by the virtio rpmsg. > This is my main concern, i would like to be sure that this service is > not related to specific needs introduced by the rmpsg char implementation: > In this case this should not be part of the rpmsg core but perhaps some > ops directly provided to the rpmsg_char on registration > (rpmsg_chrdev_register_device?)... > Arun's imminent need is for a user space client that needs to flow control the incoming data stream. But the possibility of controlling the incoming flow of data is useful in a number of situations. > > > > > > I'm uncertain of how we could implement this mechanism for virtio rpmsg, > > given that it as a transport doesn't really have a concept of > > channels/flows - but it's really useful to have! > > > > PS. rpmsg_set_signals() can be called from any rpmsg device to perform > > flow control of the communication channel. > > For my point of view this patch-set extends the rpmsg protocol to add > channel flow control. > Does it make sense to have a flow control in rpmsg protocol? > if yes, should it be linked to a channel or to the remote processor itself? > Having per-channel flow control particularly useful in scenarios where one has multiple types of data flowing over a shared underlying FIFO - such as virtio rpmsg. As this allows these different applications to limit the data rate without having to use application specific side band controls. > Extra comment: associated documentation update is missing. > Good catch, we should have a section in Documentation/rpmsg.txt describing this mechanism. Regards, Bjorn > Regards, > Arnaud > > > > > Regards, > > Bjorn > > > >> Regards > >> Arnaud > >> > >>> > >>> Changes since v1: > >>> - Split the patches as per functional areas like core, char, glink > >>> - Add set, clear mask for TIOCMSET > >>> - Merge the char signal callback and POLLPRI patches > >>> > >>> Changes since v2: > >>> - Modify the rpmsg_get_signals function prototype > >>> > >>> Changes since v3: > >>> - Correct the TICOMGET case handling as per new rpmsg_get_signals prototype > >>> - Update the rpmsg_get_signals function header > >>> > >>> Arun Kumar Neelakantam (4): > >>> rpmsg: core: Add signal API support > >>> rpmsg: glink: Add support to handle signals command > >>> rpmsg: char: Add TIOCMGET/TIOCMSET ioctl support > >>> rpmsg: char: Add signal callback and POLLPRI support > >>> > >>> drivers/rpmsg/qcom_glink_native.c | 126 ++++++++++++++++++++++++++++++++++++++ > >>> drivers/rpmsg/rpmsg_char.c | 74 +++++++++++++++++++++- > >>> drivers/rpmsg/rpmsg_core.c | 41 +++++++++++++ > >>> drivers/rpmsg/rpmsg_internal.h | 5 ++ > >>> include/linux/rpmsg.h | 26 ++++++++ > >>> 5 files changed, 269 insertions(+), 3 deletions(-) > >>>
