Re: gnumach2 & the serial port

[Roland McGrath]

> I'm quite sure that "@isa@0x02f8" is wrong.  The syntax for bus tree
> walk is for me a bit cryptic (oskit/unsupported/bus_walk_lookup.c).

It's intended to be adequately featureful and straightforward for
mechanical purposes, not intuitive.

> oskit_dump_devices() dumps following tree for sio devices:
> 
>   Current hardware tree:
>     isa.isa                Industry Standard Architecture (ISA) Bus
>       0x02f8.sio           PC serial port driver
> 
> So it should be "@>:isabus@=sio", right? 

It depends what you want.  @foo means "position string foo".  @isa@0x02f8
means exactly the second line given that tree above.  @>:isabus@=sio would
find the first sio device at whatever address, on any isabus no matter how
far down from the root bus.

So if /dev/ttyS1 should be "the COM2 serial port given canonical hardware",
then @isa@0x02f8 is right.  If it should be "the second port using the sio
driver on the first isa bus", then @>:isabus@+1=sio is right.  We don't
have a proper COM interface for serial devices, but if we had one and you
wanted "the second serial port in the system", then @+1>:serialdev would be
right.