linux-kernel - Re: [PATCH V4 0/4] Add TIOCM Signals support for RPMSG char devices

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Message-ID: <20181008162325.GA1331@tuxbook-pro>
Date:   Mon, 8 Oct 2018 09:23:25 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Arnaud Pouliquen <arnaud.pouliquen@...com>
Cc:     Arun Kumar Neelakantam <aneela@...eaurora.org>, ohad@...ery.com,
        clew@...eaurora.org, sricharan@...eaurora.org,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 0/4] Add TIOCM Signals support for RPMSG char devices

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.

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.


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.

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(-)
> >