What pokes the ISA IO port of 0x211 ?

Frantisek Rysanek
2008-04-21T11:11:23Z

Dear Everyone,

I'm dealing with an embedded PC motherboard that contains some custom
circuitry (GPIO), accessible via an ISA IO range between 0x200 and
0x218.

There's an interesting issue with this in recent Linux (tried
2.6.22.6 and 2.6.24.2): something probes IO port 0x211 on boot, which
happens to be an add-on buzzer control port - effectively the kernel
boot launches an accoustic alarm :-)

Any ideas what this could be?

Obviously it's no problem for me to write a tiny kernel module to
disable the alarm again, and I've actually verified the problem using
ioperm()+outb() from user space, but still I'd be interested to know
which particular piece of code could be probing that address...

The address decode might be implemented using some general-purpose
features of the Winbond W83627HF SuperIO (as there's no ISA in the
system, just ICH4 LPC) - but it seems quite unlikely that this would
be caused by something fiddling with the W83627 config registers.
It really seems like something writes 0xFF to IO port 0x211.

Thanks for your time and attention :-)

Frank Rysanek