tty: n_gsm: Fixed logic to decode break signal from modem status

The modem status can be one or 2 octets and contains the V.24 signals
and in the 2 octet case also the break signal.
We were improperly decoding the break signal from the modem in the
2 octet case.

Signed-off-by: Russ Gorby <russ.gorby@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 09e8c7d53af3e7d72ebfe25b45100789f4f5185a..7290394e31317fb8adfe1ebd9542fc88d4e8a4cf 100644 (file)
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -984,10 +984,22 @@ static void gsm_control_reply(struct gsm_mux *gsm, int cmd, u8 *data,
  */
 
 static void gsm_process_modem(struct tty_struct *tty, struct gsm_dlci *dlci,
-                                                       u32 modem)
+                                                       u32 modem, int clen)
 {
        int  mlines = 0;
-       u8 brk = modem >> 6;
+       u8 brk = 0;
+
+       /* The modem status command can either contain one octet (v.24 signals)
+          or two octets (v.24 signals + break signals). The length field will
+          either be 2 or 3 respectively. This is specified in section
+          5.4.6.3.7 of the  27.010 mux spec. */
+
+       if (clen == 2)
+               modem = modem & 0x7f;
+       else {
+               brk = modem & 0x7f;
+               modem = (modem >> 7) & 0x7f;
+       };
 
        /* Flow control/ready to communicate */
        if (modem & MDM_FC) {
@@ -1061,7 +1073,7 @@ static void gsm_control_modem(struct gsm_mux *gsm, u8 *data, int clen)
                        return;
        }
        tty = tty_port_tty_get(&dlci->port);
-       gsm_process_modem(tty, dlci, modem);
+       gsm_process_modem(tty, dlci, modem, clen);
        if (tty) {
                tty_wakeup(tty);
                tty_kref_put(tty);
@@ -1482,12 +1494,13 @@ static void gsm_dlci_begin_close(struct gsm_dlci *dlci)
  *     open we shovel the bits down it, if not we drop them.
  */
 
-static void gsm_dlci_data(struct gsm_dlci *dlci, u8 *data, int len)
+static void gsm_dlci_data(struct gsm_dlci *dlci, u8 *data, int clen)
 {
        /* krefs .. */
        struct tty_port *port = &dlci->port;
        struct tty_struct *tty = tty_port_tty_get(port);
        unsigned int modem = 0;
+       int len = clen;
 
        if (debug & 16)
                pr_debug("%d bytes for tty %p\n", len, tty);
@@ -1507,7 +1520,7 @@ static void gsm_dlci_data(struct gsm_dlci *dlci, u8 *data, int len)
                                if (len == 0)
                                        return;
                        }
-                       gsm_process_modem(tty, dlci, modem);
+                       gsm_process_modem(tty, dlci, modem, clen);
                /* Line state will go via DLCI 0 controls only */
                case 1:
                default: