USB: RTS/DTR signal patch for airprime driver

I encountered some problems with the airprime driver in use with a Novatel
Merlin XU870:

Closing an open Connection to e.g. /dev/ttyUSB0 doesn't reset the
RTS/DTR lines of the Modem.  Consequently, when I use minicom to
establish a connection by "ATD*99#" the modem doesn't hang up even if i
exit minicom and so I cannot reuse the modem unless I remove it and plug
it in again.

With the attached patch, the RTS/DTR lines are resetted on a close.  The
code was mainly taken from the option.c driver.

1 files changed, 47 insertions, 0 deletions

diff --git a/drivers/usb/serial/airprime.c b/drivers/usb/serial/airprime.c
index 18816bf96a4d..310a8b5f5906 100644
--- a/drivers/usb/serial/airprime.c
+++ b/drivers/usb/serial/airprime.c
@@ -44,8 +44,43 @@ struct airprime_private {
         int outstanding_urbs;
         int throttled;
         struct urb *read_urbp[NUM_READ_URBS];
+
+        /* Settings for the port */
+        int rts_state;  /* Handshaking pins (outputs) */
+        int dtr_state;
+        int cts_state;  /* Handshaking pins (inputs) */
+        int dsr_state;
+        int dcd_state;
+        int ri_state;
 };
 
+static int airprime_send_setup(struct usb_serial_port *port)
+{
+        struct usb_serial *serial = port->serial;
+        struct airprime_private *priv;
+
+        dbg("%s", __FUNCTION__);
+
+        if (port->number != 0)
+                return 0;
+
+        priv = usb_get_serial_port_data(port);
+
+        if (port->tty) {
+                int val = 0;
+                if (priv->dtr_state)
+                        val |= 0x01;
+                if (priv->rts_state)
+                        val |= 0x02;
+
+                return usb_control_msg(serial->dev,
+                                usb_rcvctrlpipe(serial->dev, 0),
+                                0x22,0x21,val,0,NULL,0,USB_CTRL_SET_TIMEOUT);
+        }
+
+        return 0;
+}
+
 static void airprime_read_bulk_callback(struct urb *urb)
 {
         struct usb_serial_port *port = urb->context;
@@ -118,6 +153,10 @@ static int airprime_open(struct usb_serial_port *port, struct file *filp)
                 usb_set_serial_port_data(port, priv);
         }
 
+        /* Set some sane defaults */
+        priv->rts_state = 1;
+        priv->dtr_state = 1;
+
         for (i = 0; i < NUM_READ_URBS; ++i) {
                 buffer = kmalloc(buffer_size, GFP_KERNEL);
                 if (!buffer) {
@@ -151,6 +190,9 @@ static int airprime_open(struct usb_serial_port *port, struct file *filp)
                 /* remember this urb so we can kill it when the port is closed */
                 priv->read_urbp[i] = urb;
         }
+
+        airprime_send_setup(port);
+
         goto out;
 
  errout:
@@ -176,6 +218,11 @@ static void airprime_close(struct usb_serial_port *port, struct file * filp)
 
         dbg("%s - port %d", __FUNCTION__, port->number);
 
+        priv->rts_state = 0;
+        priv->dtr_state = 0;
+
+        airprime_send_setup(port);
+
         for (i = 0; i < NUM_READ_URBS; ++i) {
                 usb_kill_urb (priv->read_urbp[i]);
                 kfree (priv->read_urbp[i]->transfer_buffer);