USB: serial: opticon: add write support

This patch allows data to be sent to the scanner.

Cc: Kees Stoop <kees.stoop@opticon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/opticon.c

 /*
  * Opticon USB barcode to serial driver
  *
- * Copyright (C) 2008 Greg Kroah-Hartman <gregkh@suse.de>
- * Copyright (C) 2008 Novell Inc.
+ * Copyright (C) 2008 - 2009 Greg Kroah-Hartman <gregkh@suse.de>
+ * Copyright (C) 2008 - 2009 Novell Inc.
  *
  *	This program is free software; you can redistribute it and/or
  *	modify it under the terms of the GNU General Public License version
@@ -40,8 +40,12 @@ struct opticon_private {
 	bool throttled;
 	bool actually_throttled;
 	bool rts;
+	int outstanding_urbs;
 };
 
+/* max number of write urbs in flight */
+#define URB_UPPER_LIMIT	4
+
 static void opticon_bulk_callback(struct urb *urb)
 {
 	struct opticon_private *priv = urb->context;
@@ -188,6 +192,120 @@ static void opticon_close(struct tty_struct *tty, struct usb_serial_port *port,
 	usb_kill_urb(priv->bulk_read_urb);
 }
 
+static void opticon_write_bulk_callback(struct urb *urb)
+{
+	struct opticon_private *priv = urb->context;
+	int status = urb->status;
+	unsigned long flags;
+
+	/* free up the transfer buffer, as usb_free_urb() does not do this */
+	kfree(urb->transfer_buffer);
+
+	if (status)
+		dbg("%s - nonzero write bulk status received: %d",
+		    __func__, status);
+
+	spin_lock_irqsave(&priv->lock, flags);
+	--priv->outstanding_urbs;
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	usb_serial_port_softint(priv->port);
+}
+
+static int opticon_write(struct tty_struct *tty, struct usb_serial_port *port,
+			 const unsigned char *buf, int count)
+{
+	struct opticon_private *priv = usb_get_serial_data(port->serial);
+	struct usb_serial *serial = port->serial;
+	struct urb *urb;
+	unsigned char *buffer;
+	unsigned long flags;
+	int status;
+
+	dbg("%s - port %d", __func__, port->number);
+
+	spin_lock_irqsave(&priv->lock, flags);
+	if (priv->outstanding_urbs > URB_UPPER_LIMIT) {
+		spin_unlock_irqrestore(&priv->lock, flags);
+		dbg("%s - write limit hit\n", __func__);
+		return 0;
+	}
+	priv->outstanding_urbs++;
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	buffer = kmalloc(count, GFP_ATOMIC);
+	if (!buffer) {
+		dev_err(&port->dev, "out of memory\n");
+		count = -ENOMEM;
+		goto error_no_buffer;
+	}
+
+	urb = usb_alloc_urb(0, GFP_ATOMIC);
+	if (!urb) {
+		dev_err(&port->dev, "no more free urbs\n");
+		count = -ENOMEM;
+		goto error_no_urb;
+	}
+
+	memcpy(buffer, buf, count);
+
+	usb_serial_debug_data(debug, &port->dev, __func__, count, buffer);
+
+	usb_fill_bulk_urb(urb, serial->dev,
+			  usb_sndbulkpipe(serial->dev,
+					  port->bulk_out_endpointAddress),
+			  buffer, count, opticon_write_bulk_callback, priv);
+
+	/* send it down the pipe */
+	status = usb_submit_urb(urb, GFP_ATOMIC);
+	if (status) {
+		dev_err(&port->dev,
+		   "%s - usb_submit_urb(write bulk) failed with status = %d\n",
+							__func__, status);
+		count = status;
+		goto error;
+	}
+
+	/* we are done with this urb, so let the host driver
+	 * really free it when it is finished with it */
+	usb_free_urb(urb);
+
+	return count;
+error:
+	usb_free_urb(urb);
+error_no_urb:
+	kfree(buffer);
+error_no_buffer:
+	spin_lock_irqsave(&priv->lock, flags);
+	--priv->outstanding_urbs;
+	spin_unlock_irqrestore(&priv->lock, flags);
+	return count;
+}
+
+static int opticon_write_room(struct tty_struct *tty)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	struct opticon_private *priv = usb_get_serial_data(port->serial);
+	unsigned long flags;
+
+	dbg("%s - port %d", __func__, port->number);
+
+	/*
+	 * We really can take almost anything the user throws at us
+	 * but let's pick a nice big number to tell the tty
+	 * layer that we have lots of free space, unless we don't.
+	 */
+	spin_lock_irqsave(&priv->lock, flags);
+	if (priv->outstanding_urbs > URB_UPPER_LIMIT * 2 / 3) {
+		spin_unlock_irqrestore(&priv->lock, flags);
+		dbg("%s - write limit hit\n", __func__);
+		return 0;
+	}
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	return 2048;
+}
+
 static void opticon_throttle(struct tty_struct *tty)
 {
 	struct usb_serial_port *port = tty->driver_data;
@@ -352,6 +470,8 @@ static struct usb_serial_driver opticon_device = {
 	.attach =		opticon_startup,
 	.open =			opticon_open,
 	.close =		opticon_close,
+	.write =		opticon_write,
+	.write_room = 		opticon_write_room,
 	.shutdown =		opticon_shutdown,
 	.throttle = 		opticon_throttle,
 	.unthrottle =		opticon_unthrottle,