I've recently added support for gpio on the Soekris net4801 based on  
the code from OpenBSD. If you want to play with the error LED on your  
system, do the following:

     1. Update -current sources
     2. Add the following to your kernel config:
nsclpcsio* at isa?
gscpcib* at pci? dev ? function ?
gpio* at nsclpcsio?
gpio* at gscpcib?
     3. Build a new kernel and userland (to get /usr/include/sys/ 
gpio.h and /usr/sbin/gpioctl).
     4. With a new MAKEDEV in /dev, 'sh MAKEDEV gpio'

Then, if you want to control the error LED, first configure the pin:
     # gpioctl -c 20 on pp

Now you can control the error LED.

To turn it on:
     # gpioctl 20 1
To turn it off:
     # gpioctl 20 0
To toggle the LED (eg if it's on, turn it off; if it's off, turn it on):
     # gpioctl 20 2

Have fun!

Cheers,
Jared