Re: [NILO-discuss] Zen and the art of running in real mode

[Marty C. <md...@en...>]

On Mar 8, 2005, at 1:10 PM, H. Peter Anvin wrote:
> Not all drivers *can* be modified to use in/out (i.e. portio) as 
> opposed to read/write (i.e. MMIO.)  It's a function of the hardware.

So does this mean that any loader being used with these cards would 
have to use PM to have any chance of working?

> Perhaps the first thing to do is to print a legible message if 
> something tries to call the PM entry point and/or invoke the RM entry 
> point in V86 mode.  Something asking them to report what they're 
> trying to do, and we could evaluate the importance at that point.

Is this what we think FreeBSD is doing when talking to Etherboot?

I hope these questions are at least somewhat sensible.  I am trying to 
anticipate from the perspective of someone trying to figure out what 
options they need to select to have their PXE ROM image work.

I get the feeling that success may depend on:

     - Whether there card uses MMIO or portio
     - Whether the loader they intend to use tries to:
       "call the PM entry point and/or invoke the RM entry point in V86 
mode"

Now, since most people probably don't know the answer to either of 
these questions, I think we might have to recommend options based on 
either scenarios, or most-likely-to-work options (e.g. "Try this first 
unless you are planning to boot FREEBSD" or "If you are planning to use 
RIS, check this box").

I really don't really like the idea of doing this, but until we figure 
out what the compatibility gamut of various configurations is, we might 
need to.

I have a pristine Intel EEPRO100B and a 3Com 3C905C which I use for 
testing.  Both have PXE implementations in on-board flash, and are 
useful for grossly determining compatibility of stuff, since I suspect 
these are two of the more common stacks available.

Is this analysis reasonable?  What other factors might we need to 
consider when deciding whether people should turn on various 
compatibility options.  Hopefully if we work with free software PXE 
loader developers they will help us support something reasonable.

To work with RIS but not FreeBSD would be a little, umm, strange :)

Marty