MPSAFE TTY schedule [uart vs sio]

[Marcel Moolenaar]

On Jul 4, 2008, at 6:10 AM, Takahashi Yoshihiro wrote:

> In article <20080704.063540.1210476607.imp at bsdimp.com>
> "M. Warner Losh" <imp at bsdimp.com> writes:
>
>> 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...
>
> The uart probably works for some 16550 based devices but does not work
> for other one like multi-port devices.

The design principle of uart(4) is that it does not know
about multi-port hardware. It controls a single serial
port only. For multi-port hardware you must have multiple
nodes on a bus or use an umbrella driver, such as puc(4),
quicc(4) or scc(4). Those drivers provide attachments for
every port.

I suspect that support for multi-port devices is not to
hard to do on pc98...

-- 
Marcel Moolenaar
xcllnt at mac.com