com ports in freebsd

Eric F Crist ecrist at
Wed Feb 11 11:37:19 PST 2004

On Wednesday 11 February 2004 01:23 pm, Duane Winner wrote:
> Hello,
> I have a question about how FreeBSD handles the serial ports.
> After messing around for 2 days, I finally got my PCMCIA modem working
> on my laptop. All I really had to do was to
> "cd /dev/ && ./MAKEDEV cuaa4"
> I did this because dmesg kept reporting the Megahertz modem at "sio4".
> What I don't understand is the why or how. My kernel config is still
> using the default sio0 thru sio3 devices:
> 	device          sio0    at isa? port IO_COM1 flags 0x10 irq 4
> 	device          sio1    at isa? port IO_COM2 irq 3
> 	device         sio2    at isa? disable port IO_COM3 irq 5
> 	device         sio3    at isa? disable port IO_COM4 irq 9
> So if there is now sio4 in the kernel, how is this working?
> I'm not complaining, nor looking for a solution, since I have everything
> working now.
> I'm just trying to understand how this working.
> Thanks,
> DW

If you look, sio2 and sio3 have been disabled in the kernel config.  since 
sio0 and sio1 are assigned as hardware serial devices, the first available is 
sio4 that either hasn't been disabled or isn't in use.  

Eric F Crist
AdTech Integrated Systems, Inc
(612) 998-3588
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