From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: [PATCH 4.14 31/91] tty: n_gsm: Fix DLCI handling for ADM mode if debug & 2 is not set Date: Mon, 30 Apr 2018 12:24:13 -0700 Message-ID: <20180430184005.798978596@linuxfoundation.org> References: <20180430184004.216234025@linuxfoundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <20180430184004.216234025@linuxfoundation.org> Sender: stable-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, linux-serial@vger.kernel.org, Alan Cox , Dan Williams , Jiri Prchal , Jiri Slaby , Marcel Partap , Merlijn Wajer , Michael Nazzareno Trimarchi , Michael Scott , Pavel Machek , Peter Hurley , Russ Gorby , Sascha Hauer , Sebastian Reichel , Tony Lindgren List-Id: linux-serial@vger.kernel.org 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tony Lindgren commit b2d89ad9c9682e795ed6eeb9ed455789ad6cedf1 upstream. At least on droid 4 with control channel in ADM mode, there is no response to Modem Status Command (MSC). Currently gsmtty_modem_update() expects to have data in dlci->modem_rx unless debug & 2 is set. This means that on droid 4, things only work if debug & 2 is set. Let's fix the issue by ignoring empty dlci->modem_rx for ADM mode. In the AMD mode, CMD_MSC will never respond and gsm_process_modem() won't get called to set dlci->modem_rx. And according to ts_127010v140000p.pdf, MSC is only relevant if basic option is chosen, so let's test for that too. Fixes: ea3d8465ab9b ("tty: n_gsm: Allow ADM response in addition to UA for control dlci") Cc: linux-serial@vger.kernel.org Cc: Alan Cox Cc: Dan Williams Cc: Jiri Prchal Cc: Jiri Slaby Cc: Marcel Partap Cc: Merlijn Wajer Cc: Michael Nazzareno Trimarchi Cc: Michael Scott Cc: Pavel Machek Cc: Peter Hurley Cc: Russ Gorby Cc: Sascha Hauer Cc: Sebastian Reichel Signed-off-by: Tony Lindgren Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_gsm.c | 11 +++++++++++ 1 file changed, 11 insertions(+) --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -2885,11 +2885,22 @@ static int gsmtty_modem_update(struct gs static int gsm_carrier_raised(struct tty_port *port) { struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port); + struct gsm_mux *gsm = dlci->gsm; + /* Not yet open so no carrier info */ if (dlci->state != DLCI_OPEN) return 0; if (debug & 2) return 1; + + /* + * Basic mode with control channel in ADM mode may not respond + * to CMD_MSC at all and modem_rx is empty. + */ + if (gsm->encoding == 0 && gsm->dlci[0]->mode == DLCI_MODE_ADM && + !dlci->modem_rx) + return 1; + return dlci->modem_rx & TIOCM_CD; }