[SERIAL] Convert fifosize to an unsigned int

Some UARTs have more than 255 bytes of FIFO, which can't be
represented by an unsigned char.  Change the kernel's internal
structure to be an unsigned int, but still export an unsigned char
via the TIOCGSERIAL ioctl.  If the TIOCSSERIAL ioctl provides a
fifo size of 0, assume this means "don't change" otherwise we'll
corrupt the larger fifo sizes.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/serial/mpc52xx_uart.c

@@ -728,8 +728,7 @@ mpc52xx_uart_probe(struct platform_device *dev)
 
 	spin_lock_init(&port->lock);
 	port->uartclk	= __res.bi_ipbfreq / 2; /* Look at CTLR doc */
-	port->fifosize	= 255; /* Should be 512 ! But it can't be */
-	                       /* stored in a unsigned char       */
+	port->fifosize	= 512;
 	port->iotype	= UPIO_MEM;
 	port->flags	= UPF_BOOT_AUTOCONF |
 			  ( uart_console(port) ? 0 : UPF_IOREMAP );

drivers/serial/serial_core.c

@@ -691,7 +691,8 @@ static int uart_set_info(struct uart_state *state,
 		    (new_serial.baud_base != port->uartclk / 16) ||
 		    (close_delay != state->close_delay) ||
 		    (closing_wait != state->closing_wait) ||
-		    (new_serial.xmit_fifo_size != port->fifosize) ||
+		    (new_serial.xmit_fifo_size &&
+		     new_serial.xmit_fifo_size != port->fifosize) ||
 		    (((new_flags ^ old_flags) & ~UPF_USR_MASK) != 0))
 			goto exit;
 		port->flags = ((port->flags & ~UPF_USR_MASK) |
@@ -796,7 +797,8 @@ static int uart_set_info(struct uart_state *state,
 	port->custom_divisor   = new_serial.custom_divisor;
 	state->close_delay     = close_delay;
 	state->closing_wait    = closing_wait;
-	port->fifosize         = new_serial.xmit_fifo_size;
+	if (new_serial.xmit_fifo_size)
+		port->fifosize = new_serial.xmit_fifo_size;
 	if (state->info->tty)
 		state->info->tty->low_latency =
 			(port->flags & UPF_LOW_LATENCY) ? 1 : 0;

include/linux/serial_core.h

@@ -214,10 +214,11 @@ struct uart_port {
 	unsigned char __iomem	*membase;		/* read/write[bwl] */
 	unsigned int		irq;			/* irq number */
 	unsigned int		uartclk;		/* base uart clock */
-	unsigned char		fifosize;		/* tx fifo size */
+	unsigned int		fifosize;		/* tx fifo size */
 	unsigned char		x_char;			/* xon/xoff char */
 	unsigned char		regshift;		/* reg offset shift */
 	unsigned char		iotype;			/* io access style */
+	unsigned char		unused1;
 
 #define UPIO_PORT		(0)
 #define UPIO_HUB6		(1)