I have been able to start a X server on my jornada. The stylus works,
it's possible to move the cursor with it. I have not been able to check
that the keyboard works (In order to try remote X client, I need to at
least build xhost on hpcarm, which needs all the X11 libraries, and I'm
running out of disk space)

The changes (I'll commit this soon)
- In xsrc: hpcarm is exacly like hpcmips
- In j720ssp.c: implement the WSKBDIO_GTYPE in j720kbd_ioctl()
- In the kernel config file: options WSDISPLAY_COMPAT_USL and
WSDISPLAY_COMPAT_RAWKBD

I had to manually adjust /usr/X11R6/lib/X11/fonts/misc/fonts.dir once
installed from xsrc: the default fixed font did not exist, and the
cursor font was corrupted. I'm not sure about what to do with this.

-- 
Emmanuel Dreyfus.
"Le 80x86 n'est pas si complexe - il n'a simplement pas de sens"
(Mike Johnson, responsable de la conception x86 chez AMD) 
manu@netbsd.org