[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>

2 files changed, 5 insertions, 4 deletions

diff --git a/drivers/serial/mpc52xx_uart.c b/drivers/serial/mpc52xx_uart.c
index 6459edc7f5c5..1b2cdc91c228 100644
--- a/drivers/serial/mpc52xx_uart.c
+++ b/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 );
diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index 17839e753e4c..3805f467b2f5 100644
--- a/drivers/serial/serial_core.c
+++ b/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;