* sysrq on serial console
@ 2002-09-27 23:45 Dave Hansen
2002-09-28 0:29 ` H. Peter Anvin
2002-09-28 8:06 ` Russell King
0 siblings, 2 replies; 3+ messages in thread
From: Dave Hansen @ 2002-09-27 23:45 UTC (permalink / raw)
To: Russell King, linux-kernel
Since the serial cleanups happened in 2.5, Magic Sysrq doesn't work
for me on the serial console.
It looks like the UART_LSR_BI bit needs to be set in the status
variable for the break character to be interpreted as a break in the
driver.
I doubt that it is actually broken, but it isn't immediately obvious
how that bit gets set. Is there something that I should have set when
the device was initialized to make sure that UART_LSR_BI is asserted
in "status" when the interrupt occurs?
--
Dave Hansen
haveblue@us.ibm.com
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: sysrq on serial console
2002-09-27 23:45 sysrq on serial console Dave Hansen
@ 2002-09-28 0:29 ` H. Peter Anvin
2002-09-28 8:06 ` Russell King
1 sibling, 0 replies; 3+ messages in thread
From: H. Peter Anvin @ 2002-09-28 0:29 UTC (permalink / raw)
To: linux-kernel
Followup to: <3D94ED88.5040407@us.ibm.com>
By author: Dave Hansen <haveblue@us.ibm.com>
In newsgroup: linux.dev.kernel
>
> Since the serial cleanups happened in 2.5, Magic Sysrq doesn't work
> for me on the serial console.
>
It's been broken for me in several 2.4 versions as well. This is
highly troublesome.
> It looks like the UART_LSR_BI bit needs to be set in the status
> variable for the break character to be interpreted as a break in the
> driver.
>
> I doubt that it is actually broken, but it isn't immediately obvious
> how that bit gets set. Is there something that I should have set when
> the device was initialized to make sure that UART_LSR_BI is asserted
> in "status" when the interrupt occurs?
--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt <amsp@zytor.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: sysrq on serial console
2002-09-27 23:45 sysrq on serial console Dave Hansen
2002-09-28 0:29 ` H. Peter Anvin
@ 2002-09-28 8:06 ` Russell King
1 sibling, 0 replies; 3+ messages in thread
From: Russell King @ 2002-09-28 8:06 UTC (permalink / raw)
To: Dave Hansen; +Cc: linux-kernel
On Fri, Sep 27, 2002 at 04:45:12PM -0700, Dave Hansen wrote:
> It looks like the UART_LSR_BI bit needs to be set in the status
> variable for the break character to be interpreted as a break in the
> driver.
That is correct; that is how the UART reports a break character.
> I doubt that it is actually broken, but it isn't immediately obvious
> how that bit gets set. Is there something that I should have set when
> the device was initialized to make sure that UART_LSR_BI is asserted
> in "status" when the interrupt occurs?
Now. Its a status bit from the UART LSR register itself, read from
serial8250_handle_port() and receive_chars(). It will cause an
interrupt any time that the receive interrupt is enabled, ie when
the port is open by user space.
--
Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux
http://www.arm.linux.org.uk/personal/aboutme.html
^ permalink raw reply [flat|nested] 3+ messages in thread
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2002-09-28 0:29 ` H. Peter Anvin
2002-09-28 8:06 ` Russell King
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