Messages in this thread | | | From | Lars Poeschel <> | Subject | Re: [RFC DO NOT MERGE] tty: n_gsm: support buggy modem | Date | Tue, 07 Jan 2014 17:58:59 +0100 |
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Am Dienstag, 7. Januar 2014, 06:20:50 schrieb Greg KH: > On Tue, Jan 07, 2014 at 02:05:26PM +0100, Lars Poeschel wrote: > > From: Lars Poeschel <poeschel@lemonage.de> > > > > This is obiviously a bad patch. Do not merge it! > > I have a GSM Modem (Quectel M95 Revision: M95AR01A11) that I have a > > problem > > with when using the n_gsm mux line discipline. After attaching the line > > discipline and opening a muxed channel, the open never returns. The > > problem is that the tty code waits for the TIOCM_CD flag to be set. > > According to the 3GPP TS 07.10 specification the modem can set this > > virtual flag by setting the DV bit in it's modem status control message. > > My modem sends the modem status command, but this DV bit is not set. With > > this patch the modem and the whole mux is working fine. Another way > > makeing all this work is setting the carrier_raised function to NULL. The > > tty code assumes that everything is alright then. > > My question is: What could be the best way to support this modem in > > mailine > > kernel ? I do not see a way to detect this buggy modem inside the line > > discipline and use this patch's method as a work around then. But the > > detection would only be possible using AT command before the line > > discipline is attached or using the muxed channel after the mux is set > > up. > > Adding some n_gsm.c authors to the cc: > > Also, what kernel version are you using?
Sorry, I forgot this. I am using 3.12. After your mail I tried 3.13-rc7. It behaves exactly the same.
> > --- > > diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c > > index c0f76da..a1a6f57 100644 > > --- a/drivers/tty/n_gsm.c > > +++ b/drivers/tty/n_gsm.c > > @@ -1061,6 +1061,7 @@ static void gsm_process_modem(struct tty_struct > > *tty, struct gsm_dlci *dlci,> > > mlines |= TIOCM_RI; > > > > if (modem & MDM_DV) > > > > mlines |= TIOCM_CD; > > > > + mlines |= TIOCM_CD; > > > > /* Carrier drop -> hangup */ > > if (tty) {
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