[iPAQ] stowaway problem on familiar 0.5 solved

At LinuxWorld I met with Jim Gettys, Russell Nelson, and Edward (whose
last name I didn't catch). Together they solved my
stowaway-under-familiar-0.5 mystery, and it's working like a charm
now!

I'm still not clear exactly which steps were needed, but here's a
summary of the needed steps.

- The h3600_stowaway kernel module must be loaded. Check with lsmod.
  After installing the stowaway-module ipkg, this was already taken
  care of; this was *not* my problem.

- /dev/stowaway must exist as a special device. This is automatically
  taken care of when the h3600_stowaway kernel module is loaded; check
  that /proc/devices lists the same major device number as "ls -l
  /dev/stowaway" shows. This was *not* my problem.

- To enable the stowaway, /dev/stowaway must be opened; easiest is "cat
  /dev/stowaway". My problem here was that this always gave a 'device
  busy" error or equivalent. We found that two conditions are
  necessary for this to succeed:

  - No getty should be running. In my particular case, we solved this
    by introducing a new run level, 4, which is identical to run level
    2 except it doesn't run a getty, and making this the default
    runlevel. (Simply killing the getty process isn't enough, since
    the default inittab entry says "respawn" which will restart the
    getty when it dies.)

  - The kernel must not be using the serial port for console messages.
    This was the most baffling part. We fiddled with linuxargs in the
    boot loader and with /boot/params to remove and them put back the
    "console=/dev/ttySA0" part. Somehow, with that part in, "cat
    /dev/stowaway" caused a "device busy" error; but with it removed,
    the X11 server wouldn't start. Putting it back in made both
    problems disappear. Mysterious...!

Hope this helps anyone else with a stowaway keyboard for their iPAQ.
Once it works, it's pretty cool!

BTW, the most insane iPAQ idea at the show came from Michael Tiemann:
after seeing that Russ owned *two* iPAQs, he thought it would be cool
to be able to use them together in dual display mode. The infrared
ports should be able to do the necessary communication (with a mirror
or perhaps a sheet of white paper). Jim Gettys thought it might be
done next year, when his cooperating X server project is done. :-)

--Guido van Rossum (home page: http://www.python.org/~guido/)
Received on Thu Jan 31 08:42:23 2002