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

[Olaf Hering <olh@suse.de>]

If you can queue this up in -mm for a decade or two, just to make sure
it doesnt make some setup unhappy.


a POWER4 system in 'full-system-partition' mode has the console device
on ttyS0. But the user interface to the Linux system console may still
be on the hardware management console (HMC). If this is the case, there
is no way to send a break to trigger a sysrq.
Other setups do already use 'ctrl o' to trigger sysrq. This includes iSeries
virtual console on tty1, and pSeries LPAR console on hvc0 or hvsi0.

'ctrl o' is currently mapped to 'flush output', see 'stty -a'

Signed-off-by: Olaf Hering <olh@suse.de>

 drivers/serial/8250.c |    7 +++++++
 1 files changed, 7 insertions(+)

Index: linux-2.6.15-rc5-olh/drivers/serial/8250.c
===================================================================
--- linux-2.6.15-rc5-olh.orig/drivers/serial/8250.c
+++ linux-2.6.15-rc5-olh/drivers/serial/8250.c
@@ -1154,6 +1154,13 @@ 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, but only on the system console */
+		if (ch == '\x0f' && uart_handle_break(&up->port))
+			goto ignore_char;
+#endif
+
 		flag = TTY_NORMAL;
 		up->port.icount.rx++;
 
-- 
short story of a lazy sysadmin:
 alias appserv=wotan