tty: n_gsm: Fix DLCI handling for ADM mode if debug & 2 is not set

[muen/linux.git] / drivers / tty / n_gsm.c

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 7b1f8636f8e9b44690f68b4f03cf0c722ea30d41..1dbe27c9946c16578a6ad0f82313c4adf797aef0 100644 (file)
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2871,11 +2871,22 @@ static int gsmtty_modem_update(struct gsm_dlci *dlci, u8 brk)
 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;
 }