MPSAFE TTY schedule [uart vs sio]

[M. Warner Losh]

In message: <993E865A-A426-4036-9E09-A87D7474DE80 at mac.com>
            Marcel Moolenaar <xcllnt at mac.com> writes:
: 
: On Jul 3, 2008, at 2:09 PM, Sam Leffler wrote:
: 
: >> But I just got told sio(4) is required for pc98, because uart(4) is  
: >> not
: >> supported there. This means I'll seriously consider porting sio(4)  
: >> one
: >> of these days. It's no biggie, even though I think someone could  
: >> better
: >> take the effort to extend uart(4).
: >>
: >
: > I would suggest first investigating how difficult it is to port uart  
: > to pc98.  Given that we're broadening our platform support having a  
: > single serial driver seems preferable.
: 
: I looked into it in 2003 but since I don't have any hardware,
: I wasn't the one able to do it. I think the fundamental problem
: is that the BRG is not part of the UART itself and needs a
: separate handle or even (tag, handle) pair to access. That's as
: far as I know the only big thing about the work.
: 
: For me not having access to the hardware is a showstopper for
: looking into it myself.

Do you need physical access?  I have a pc98 machine I can put back on
the network.  It has the 8251 chip in it.  It also has a 16550 part as
well since it is a later model which had both...

I believe that uart works for the 16550 part, but haven't tried it
lately...

Warner