tty: n_gsm: expose gsmtty device nodes at ldisc open time

The n_gsm driver being an ldisc, does not provide a convenient method
e.g. udev to create the tty device nodes automatically when the ldisc
is opened.

The TTY device nodes are now created via calls to tty_register_device
from the ldisc open.

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

1 files changed, 17 insertions, 2 deletions

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 09e8c7d53af3..b288ff6cb812 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -169,6 +169,7 @@ struct gsm_control {
 struct gsm_mux {
         struct tty_struct *tty;         /* The tty our ldisc is bound to */
         spinlock_t lock;
+        unsigned int num;
 
         /* Events on the GSM channel */
         wait_queue_head_t event;
@@ -250,6 +251,8 @@ struct gsm_mux {
 static struct gsm_mux *gsm_mux[MAX_MUX];        /* GSM muxes */
 static spinlock_t gsm_mux_lock;
 
+static struct tty_driver *gsm_tty_driver;
+
 /*
  *      This section of the driver logic implements the GSM encodings
  *      both the basic and the 'advanced'. Reliable transport is not
@@ -1996,6 +1999,7 @@ int gsm_activate_mux(struct gsm_mux *gsm)
         spin_lock(&gsm_mux_lock);
         for (i = 0; i < MAX_MUX; i++) {
                 if (gsm_mux[i] == NULL) {
+                        gsm->num = i;
                         gsm_mux[i] = gsm;
                         break;
                 }
@@ -2101,13 +2105,20 @@ static int gsmld_output(struct gsm_mux *gsm, u8 *data, int len)
 
 static int gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 {
-        int ret;
+        int ret, i;
+        int base = gsm->num << 6; /* Base for this MUX */
 
         gsm->tty = tty_kref_get(tty);
         gsm->output = gsmld_output;
         ret =  gsm_activate_mux(gsm);
         if (ret != 0)
                 tty_kref_put(gsm->tty);
+        else {
+                /* Don't register device 0 - this is the control channel and not
+                   a usable tty interface */
+                for (i = 1; i < NUM_DLCI; i++)
+                        tty_register_device(gsm_tty_driver, base + i, NULL);
+        }
         return ret;
 }
 
@@ -2122,7 +2133,12 @@ static int gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 
 static void gsmld_detach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 {
+        int i;
+        int base = gsm->num << 6; /* Base for this MUX */
+
         WARN_ON(tty != gsm->tty);
+        for (i = 1; i < NUM_DLCI; i++)
+                tty_unregister_device(gsm_tty_driver, base + i);
         gsm_cleanup_mux(gsm);
         tty_kref_put(gsm->tty);
         gsm->tty = NULL;
@@ -2712,7 +2728,6 @@ static int gsmtty_break_ctl(struct tty_struct *tty, int state)
         return gsmtty_modem_update(dlci, encode);
 }
 
-static struct tty_driver *gsm_tty_driver;
 
 /* Virtual ttys for the demux */
 static const struct tty_operations gsmtty_ops = {