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    SubjectRe: A question about break and sysrq on a serial console (2.6.19.1)
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    On Thu, 2007-01-18 at 16:47 +0000, Russell King wrote:
    > On Thu, Jan 18, 2007 at 08:19:47AM -0800, Brian Beattie wrote:
    > > On Thu, 2007-01-18 at 09:13 +0000, Russell King wrote:
    > > > On Wed, Jan 17, 2007 at 03:56:54PM -0800, Brian Beattie wrote:
    > > > > I'm trying to do a SYSRQ over a serial console. As I understand it a
    > > > > break will do that, but I'm not seeing the SYSRQ. In looking at
    > > > > uart_handle_break() in drivers/serial/8250.c it looks like the code will
    > > > > toggle port->sysrq, rather than just setting it when the port is a
    > > > > console. I think the correct code would be to move the "port->sysrq =
    > > > > 0;" to follow the closing brace on the next line, or am I missing
    > > > > something.
    > > >
    > > > Thereby preventing the action of <break> (which may be to cause a SAK
    > > > event, which would be rather important on a console to ensure that
    > > > you're really logging in rather than typing your password into another
    > > > users program which just looks like a login program.)
    > > >
    > > > Note that the sequence for sysrq is:
    > > >
    > > > (non-break characters or nothing) <break> <sysrq-char>
    > > >
    > > well the code as is, is not working. Printk's tell me that
    > > uart_handle_break() is called repeatedly while the break condition is
    > > active, toggling port->sysrq so that it's a 50/50 chance on whether
    > > port->sysrq will be set or cleared when the break condition ends. On
    > > the other hand the 8250 break condition handling code is not working
    > > anyway, so the problem may be that the 8250 code is not calling
    > > uart_handle_break() correctly.
    >
    > Please learn to use the "reply to all" button when using mailing lists.
    I don't post much to LKML, I realized after I hit send I needed to reply
    all.
    >
    > Works fine here. Which UART are you actually using? At a guess, it's
    > probably a bad clone which does not have a correct break implementation.

    it's the built-in mpc8349 powerpc uart.

    >
    --
    Brian Beattie
    Firmware Engineer
    APCON, Inc.
    BrianB@apcon.com

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