USB: serial: io_edgeport: drop buffer-callback sanity checks

The driver write_room and chars_in_buffer callbacks used to incorrectly
return a negative errno in case they were called while or after the port
had been closed. The return value was later changed to zero by commit
d76f2f44 ("io_edgeport: Fix various bogus returns to the tty
layer") but the bogus sanity checks were left in place as were the
outdated function-header comments.

These callbacks will never be called for an uninitialised port so drop
the unnecessary sanity checks and the outdated comments.
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NJohan Hovold <johan@kernel.org>

drivers/usb/serial/io_edgeport.c

@@ -1351,9 +1351,7 @@ static void send_more_port_data(struct edgeport_serial *edge_serial,
 /*****************************************************************************
  * edge_write_room
  *	this function is called by the tty driver when it wants to know how
- *	many bytes of data we can accept for a specific port. If successful,
- *	we return the amount of room that we have for this port	(the txCredits)
- *	otherwise we return a negative error number.
+ *	many bytes of data we can accept for a specific port.
  *****************************************************************************/
 static unsigned int edge_write_room(struct tty_struct *tty)
 {
@@ -1362,16 +1360,6 @@ static unsigned int edge_write_room(struct tty_struct *tty)
 	unsigned int room;
 	unsigned long flags;
 
-	if (edge_port == NULL)
-		return 0;
-	if (edge_port->closePending)
-		return 0;
-
-	if (!edge_port->open) {
-		dev_dbg(&port->dev, "%s - port not opened\n", __func__);
-		return 0;
-	}
-
 	/* total of both buffers is still txCredit */
 	spin_lock_irqsave(&edge_port->ep_lock, flags);
 	room = edge_port->txCredits - edge_port->txfifo.count;
@@ -1387,9 +1375,6 @@ static unsigned int edge_write_room(struct tty_struct *tty)
  *	this function is called by the tty driver when it wants to know how
  *	many bytes of data we currently have outstanding in the port (data that
  *	has been written, but hasn't made it out the port yet)
- *	If successful, we return the number of bytes left to be written in the
- *	system,
- *	Otherwise we return a negative error number.
  *****************************************************************************/
 static unsigned int edge_chars_in_buffer(struct tty_struct *tty)
 {
@@ -1398,16 +1383,6 @@ static unsigned int edge_chars_in_buffer(struct tty_struct *tty)
 	unsigned int num_chars;
 	unsigned long flags;
 
-	if (edge_port == NULL)
-		return 0;
-	if (edge_port->closePending)
-		return 0;
-
-	if (!edge_port->open) {
-		dev_dbg(&port->dev, "%s - port not opened\n", __func__);
-		return 0;
-	}
-
 	spin_lock_irqsave(&edge_port->ep_lock, flags);
 	num_chars = edge_port->maxTxCredits - edge_port->txCredits +
 						edge_port->txfifo.count;