Cross posted to current-users, 'cos my investigations show the problem 
isn't port specific.

> In article <199812151107.LAA28209@sun52.NIS.cambridge> richard.earnshaw@arm.com writes:
> >
> >I resupped the kernel last night, and sure enough, this seems to have 
> >solved my pppd lockup, but now all my xterms are dying at startup with the 
> >error:
> >
> >xterm: Error 23, errno 25, inappropriate ioctl for device
> >
> >I notice that a lot of new code has been committed for compat_43 support?  
> >Could this be related (my xterm binaries are quite old, around 1.3 alpha 
> >vintage)?  Is compat_43 on by default, or does it need to be added to the 
> >config files as needed?
> 
> 
> Add to config files as needed.
> 

I checked my config last night.  It already had COMPAT_43 defined in it.  
I tried removing it completely and the problem persisted.  So a build a 
kernel with -DCOMPAT_43 done as an option to the compiler and the problem 
went away.

Further investigation showed that compat/common/tty_43.c, kern/tty.c and 
kern/tty_pty.c all contain code that is conditional on COMPAT_OLDTTY which 
is defined in sys/tty.h if COMPAT_43 is defined.  However, since none of 
the above files include the new opt_compat_43.h they don't get compiled 
correctly.

I think sys/tty.h should #include the new opt_compat_43.h as it does the 
other opt_compat_... include files.

Richard.