serial/8250: Add support for RS485 IOCTLs

This patch allow the users of the 8250 infrastructure to define a
handler for RS485 configration.

If no handler is defined the 8250 driver will work as usual.
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Acked-by: Alan Cox <alan@linux.intel.com>
--
v2:Change suggested by Alan "One Thousand Gnomes":
- Move rs485 structure further down on the uart_8250_port structure

 drivers/tty/serial/8250/8250_core.c | 39 +++++++++++++++++++++++++++++++++++++
 include/linux/serial_8250.h         |  3 +++
 2 files changed, 42 insertions(+)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_core.c

@@ -2843,6 +2843,42 @@ serial8250_verify_port(struct uart_port *port, struct serial_struct *ser)
 	return 0;
 }
 
+static int serial8250_ioctl(struct uart_port *port, unsigned int cmd,
+			   unsigned long arg)
+{
+	struct uart_8250_port *up =
+		container_of(port, struct uart_8250_port, port);
+	int ret;
+	struct serial_rs485 rs485_config;
+
+	if (!up->rs485_config)
+		return -ENOIOCTLCMD;
+
+	switch (cmd) {
+	case TIOCSRS485:
+		if (copy_from_user(&rs485_config, (void __user *)arg,
+				   sizeof(rs485_config)))
+			return -EFAULT;
+
+		ret = up->rs485_config(up, &rs485_config);
+		if (ret)
+			return ret;
+
+		memcpy(&up->rs485, &rs485_config, sizeof(rs485_config));
+
+		return 0;
+	case TIOCGRS485:
+		if (copy_to_user((void __user *)arg, &up->rs485,
+				 sizeof(up->rs485)))
+			return -EFAULT;
+		return 0;
+	default:
+		break;
+	}
+
+	return -ENOIOCTLCMD;
+}
+
 static const char *
 serial8250_type(struct uart_port *port)
 {
@@ -2872,6 +2908,7 @@ static struct uart_ops serial8250_pops = {
 	.request_port	= serial8250_request_port,
 	.config_port	= serial8250_config_port,
 	.verify_port	= serial8250_verify_port,
+	.ioctl		= serial8250_ioctl,
 #ifdef CONFIG_CONSOLE_POLL
 	.poll_get_char = serial8250_get_poll_char,
 	.poll_put_char = serial8250_put_poll_char,
@@ -3388,6 +3425,8 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
 		uart->port.fifosize	= up->port.fifosize;
 		uart->tx_loadsz		= up->tx_loadsz;
 		uart->capabilities	= up->capabilities;
+		uart->rs485_config	= up->rs485_config;
+		uart->rs485		= up->rs485;
 
 		/* Take tx_loadsz from fifosize if it wasn't set separately */
 		if (uart->port.fifosize && !uart->tx_loadsz)

include/linux/serial_8250.h

@@ -96,10 +96,13 @@ struct uart_8250_port {
 	unsigned char		msr_saved_flags;
 
 	struct uart_8250_dma	*dma;
+	struct serial_rs485     rs485;
 
 	/* 8250 specific callbacks */
 	int			(*dl_read)(struct uart_8250_port *);
 	void			(*dl_write)(struct uart_8250_port *, int);
+	int			(*rs485_config)(struct uart_8250_port *,
+						struct serial_rs485 *rs485);
 };
 
 static inline struct uart_8250_port *up_to_u8250p(struct uart_port *up)