[RFC] [PATCH] Adding ctrl-o sysrq hack support to 8250 driver

[Sachin Sant <sachinp@in.ibm.com>]

The following patch will allow a user to use sysrq keys over a serial 
console using the ctrl-o key sequence. This is similar to functionality 
provided by the hvc console drivers on PPC boxes.


Signed-off-by: Sachin Sant <sachinp@in.ibm.com>

diff -Naurp linux-2.6.14.3/drivers/serial/8250.c linux-2.6.14.3-new/drivers/serial/8250.c
--- linux-2.6.14.3/drivers/serial/8250.c	2005-11-11 11:03:12.000000000 +0530
+++ linux-2.6.14.3-new/drivers/serial/8250.c	2005-11-17 15:12:42.000000000 +0530
@@ -1084,6 +1084,23 @@ receive_chars(struct uart_8250_port *up,
 			 */
 		}
 		ch = serial_inp(up, UART_RX);
+
+#if defined(CONFIG_MAGIC_SYSRQ) && defined(CONFIG_SERIAL_CORE_CONSOLE)
+		/* Handle the SysRq ^O Hack */
+		if (ch == '\x0f') {
+			up->port.sysrq = jiffies + HZ*5;
+			goto ignore_char; 
+		}
+		if (up->port.sysrq) {
+			int swallow;
+			spin_unlock(&up->port.lock);
+			swallow = uart_handle_sysrq_char(&up->port, ch, regs);
+			spin_lock(&up->port.lock);
+			if (swallow)
+				goto ignore_char;
+		}
+#endif /* CONFIG_MAGIC_SYSRQ && CONFIG_SERIAL_CORE_CONSOLE */
+
 		flag = TTY_NORMAL;
 		up->port.icount.rx++;