On Mon, 7 Nov 2022 at 12:59, Manivannan Sadhasivam <mani@xxxxxxxxxx> wrote: > > + Loic > > On Tue, Sep 20, 2022 at 04:23:25PM +0200, Daniele Palmas wrote: > > Hello all, > > > > I'm looking for some guidance related to a possible MHI client for > > serial ports signals management implementation. > > > > Testing the AT channels with Telit modems I noted that unsolicited > > indications do not show: the root cause for this is DTR not set for > > those ports through MHI channels 18/19, something that with current > > upstream code can't be done due to the missing DTR client driver. > > > > I currently have an hack, based on the very first mhi stack submission > > (see https://lore.kernel.org/lkml/1524795811-21399-2-git-send-email-sdias@xxxxxxxxxxxxxx/#Z31drivers:bus:mhi:core:mhi_dtr.c), > > solving my issue, but I would like to understand which would be the > > correct way, so maybe I can contribute some code. > > > > Should the MHI DTR client be part of the WWAN subsystem? > > Yes, since WWAN is going to be the consumer of this channel, it makes sense to > host the client driver there. Agree. > > > If yes, does it make sense to have an associated port exposed as a char > > device? > > If the goal is to control the DTR settings from userspace, then you can use > the "AT" chardev node and handle the DTR settings in this client driver. > Because at the end of the day, user is going to read/write from AT port only. > Adding one more ctrl port and have it configured before using AT port is going > to be a pain. > > Thanks, > Mani > > > I guess the answer is no, since it should be used just by the AT ports > > created by mhi_wwan_ctrl, but I'm not sure if that's possible. > > > > Or should the DTR management be somehow part of the MHI stack and > > mhi_wwan_ctrl interacts with that through exported functions? Is this DTR thing Telit specific? Noticed you're using the IP_CTRL channel for this, do you have more information about the protocol to use? At first glance, I would say you can create a simple driver for IP_CTRL channel (that could be part of mhi_wwan_ctrl), but instead of exposing it rawly to the user, simply enable DTR unconditionally at probe time? Regards, Loic
