Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751808AbaAGOUv (ORCPT ); Tue, 7 Jan 2014 09:20:51 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:55270 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751057AbaAGOUd (ORCPT ); Tue, 7 Jan 2014 09:20:33 -0500 Date: Tue, 7 Jan 2014 06:20:50 -0800 From: Greg KH To: Lars Poeschel Cc: jslaby@suse.cz, linux-kernel@vger.kernel.org, xiaojin , Ken Mills , Alan Cox , Dirkjan Bussink Subject: Re: [RFC DO NOT MERGE] tty: n_gsm: support buggy modem Message-ID: <20140107142050.GB32491@kroah.com> References: <4386658.RncifLMAGy@lem-wkst-02> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4386658.RncifLMAGy@lem-wkst-02> User-Agent: Mutt/1.5.22 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 07, 2014 at 02:05:26PM +0100, Lars Poeschel wrote: > From: Lars Poeschel > > 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? thanks, greg k-h > > Thanks, > Lars > --- > 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) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/