Re: [PATCH] Stop pmac_zilog from abusing 8250's device numbers.

David Lang
2007-04-04T02:25:55Z

On Tue, 3 Apr 2007, Valdis.Kletnieks@vt.edu wrote:

> On Tue, 03 Apr 2007 16:09:08 PDT, Brad Boyer said:
>
>> an abstraction of "serial port" as far as the user is concerned. On
>> Solaris, I can say "/dev/term/a" and know that I will get the first
>> serial port if it is available without needing to care if it is the
>> zs, se or asy driver talking to the hardware.
>
> This is fine if you're trying to boot and find your system console.
>
> It blows complete chunks if the port you're trying to find is the
> first port on the special serial card that supports speeds above 115kbaud
> because we have a real-time constraint, and even at 115k you fall short
> on the timing budget (actual real-life issue we hit on an SGI running IRIX
> a number of years ago. Blowing the budget often resulted in a 3,000 pound
> motion base to turn into a 3,000 pound jackhammer:
> http://www.sv.vt.edu/future/cave/resprj/crane/crane_thor/2001FebReport.html
> http://www.moog.com/Media/1/6D2000E500-395_1102.pdf
>

but when you are looking for this port, you would lookup which port it is, make
something active on that port (if only a getty), and then confirm the port by
plugging into it and testing it.

in other words, if you have a special constraint you will have to pay attention
to the hardware to make sure it meets those requriements.

this is no different then the fact that many motherboards contain a 100Mb
ethernet port as well as a pair of 1Gb ethernet ports. if you need speeds above
100Mb you better make sure your useing the right port, but we don't name network
ports based on the type of card.

David Lang