USB: serial: omninet: use generic write implementation

Now that the endpoint-port mapping has been properly set up during
probe, we can switch to using the more efficient generic write
implementation.

Note that this currently means that chars_in_buffer now overcounts
slightly as we always write a full endpoint-sized packet.

Also add a copyright entry.
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/omninet.c

 /*
  * USB ZyXEL omni.net LCD PLUS driver
  *
+ * Copyright (C) 2013,2017 Johan Hovold <johan@kernel.org>
+ *
  *	This program is free software; you can redistribute it and/or
  *	modify it under the terms of the GNU General Public License version
  *	2 as published by the Free Software Foundation.
@@ -32,10 +34,8 @@
 
 /* function prototypes */
 static void omninet_process_read_urb(struct urb *urb);
-static void omninet_write_bulk_callback(struct urb *urb);
-static int  omninet_write(struct tty_struct *tty, struct usb_serial_port *port,
-				const unsigned char *buf, int count);
-static int  omninet_write_room(struct tty_struct *tty);
+static int omninet_prepare_write_buffer(struct usb_serial_port *port,
+				void *buf, size_t count);
 static int omninet_calc_num_ports(struct usb_serial *serial,
 				struct usb_serial_endpoints *epds);
 static int omninet_port_probe(struct usb_serial_port *port);
@@ -59,10 +59,8 @@ static struct usb_serial_driver zyxel_omninet_device = {
 	.calc_num_ports =	omninet_calc_num_ports,
 	.port_probe =		omninet_port_probe,
 	.port_remove =		omninet_port_remove,
-	.write =		omninet_write,
-	.write_room =		omninet_write_room,
-	.write_bulk_callback =	omninet_write_bulk_callback,
 	.process_read_urb =	omninet_process_read_urb,
+	.prepare_write_buffer =	omninet_prepare_write_buffer,
 };
 
 static struct usb_serial_driver * const serial_drivers[] = {
@@ -157,81 +155,24 @@ static void omninet_process_read_urb(struct urb *urb)
 	tty_flip_buffer_push(&port->port);
 }
 
-static int omninet_write(struct tty_struct *tty, struct usb_serial_port *port,
-					const unsigned char *buf, int count)
+static int omninet_prepare_write_buffer(struct usb_serial_port *port,
+					void *buf, size_t count)
 {
 	struct omninet_data *od = usb_get_serial_port_data(port);
-	struct omninet_header *header = (struct omninet_header *)
-					port->write_urb->transfer_buffer;
-	int			result;
-
-	if (count == 0) {
-		dev_dbg(&port->dev, "%s - write request of 0 bytes\n", __func__);
-		return 0;
-	}
-
-	if (!test_and_clear_bit(0, &port->write_urbs_free)) {
-		dev_dbg(&port->dev, "%s - already writing\n", __func__);
-		return 0;
-	}
-
-	count = (count > OMNINET_PAYLOADSIZE) ? OMNINET_PAYLOADSIZE : count;
+	struct omninet_header *header = buf;
 
-	memcpy(port->write_urb->transfer_buffer + OMNINET_HEADERLEN,
-								buf, count);
+	count = min_t(size_t, count, OMNINET_PAYLOADSIZE);
 
-	usb_serial_debug_data(&port->dev, __func__, count,
-			      port->write_urb->transfer_buffer);
+	count = kfifo_out_locked(&port->write_fifo, buf + OMNINET_HEADERLEN,
+			count, &port->lock);
 
 	header->oh_seq = od->od_outseq++;
 	header->oh_len = count;
 	header->oh_xxx = 0x03;
 	header->oh_pad = 0x00;
 
-	/* send the data out the bulk port, always 64 bytes */
-	port->write_urb->transfer_buffer_length = OMNINET_BULKOUTSIZE;
-
-	result = usb_submit_urb(port->write_urb, GFP_ATOMIC);
-	if (result) {
-		set_bit(0, &port->write_urbs_free);
-		dev_err_console(port,
-			"%s - failed submitting write urb, error %d\n",
-			__func__, result);
-	} else
-		result = count;
-
-	return result;
-}
-
-
-static int omninet_write_room(struct tty_struct *tty)
-{
-	struct usb_serial_port *port = tty->driver_data;
-	int room = 0; /* Default: no room */
-
-	if (test_bit(0, &port->write_urbs_free))
-		room = port->bulk_out_size - OMNINET_HEADERLEN;
-
-	dev_dbg(&port->dev, "%s - returns %d\n", __func__, room);
-
-	return room;
-}
-
-static void omninet_write_bulk_callback(struct urb *urb)
-{
-/*	struct omninet_header	*header = (struct omninet_header  *)
-						urb->transfer_buffer; */
-	struct usb_serial_port 	*port   =  urb->context;
-	int status = urb->status;
-
-	set_bit(0, &port->write_urbs_free);
-	if (status) {
-		dev_dbg(&port->dev, "%s - nonzero write bulk status received: %d\n",
-			__func__, status);
-		return;
-	}
-
-	usb_serial_port_softint(port);
+	/* always 64 bytes */
+	return OMNINET_BULKOUTSIZE;
 }
 
 module_usb_serial_driver(serial_drivers, id_table);