I'm having some problems getting the AST 4-port driver working.  I'm
running 1.0A from late May (1.54 com.c).  I've configured the com
driver as follows:

com0    at isa? port 0x3f8 irq 4        # standard PC serial ports
com1    at isa? port 0x2f8 irq 3
ast0    at isa? port 0x2a0 irq 5        # AST 4-port serial cards
com*    at ast? slave ? flags 1

When the system boots up, it finds all 4 UARTs on the board and
correctly probes them as ns16550's.  However, as soon as ttyflags
tries to write to the port, the system panics.

A bit of poking around with ddb reveals that astintr() is calling
comintr() with a NULL pointer, which would seem to indicate that the
sc_slaves[n] pointer for that port is NULL.  I put a debugging
statement into astattach() that prints the value of this pointer just
after config_attach() gets called, and the only port that gets a
non-zero slave pointer is port 1 (of 0-3).  I don't know that much
about the autoconf stuff in the kernel, so I'm sort of at a loss as to
where to go from there...

Does the ast driver work?  (Well, is it *supposed* to work?)  Do I
have something misconfigured?  Is anybody actually using this?

-Marc