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    SubjectRe: [PATCH] Adding ctrl-o sysrq hack support to 8250 driver
    On Fri, Dec 09, 2005 at 03:05:59PM +0100, Olaf Hering wrote:
    > 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.

    So it's a POWER4 problem.

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

    Eww... If you can't use a serial break, why can't you use an
    established control character like ctrl-] (telnet) or [enter]~ (ssh) ?

    If you really want to use ctrl-o, could you make a way that pressing
    ctrl-o twice sends a single ctrl-o to the process attached to the

    > Signed-off-by: Olaf Hering <>
    > 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 it is a POWER4-only problem, why isn't there a dependency on
    CONFIG_POWER4 over here? I don't like to have the ctrl-o sysrq stuff
    enabled on my regular PC if it only matters to some rare (in absolute
    numbers) system.


    +-- Erik Mouw -- -- +31 70 370 12 90 --
    | Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands
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