[9fans] ne2000

[David Hogan dhog@lore.plan9.cs.su.oz.au]

Well, I have this PnP ethernet card which is supposedly
NE2000 compatible.  Naturally I want everything to
be "Plug and Play", ie once the kernel's recognized the
card (using my PnP support) and configured the irq and io
port, it should know all it needs to know, without any
special stuff in "plan9.ini".

There are two problems.  First, I need to know how much
memory the card has.  It's occured to me that I can
probably get this by using standard memory sizing
techniques.  However, I'd like to know a bit more about
the NE2000 "standard" (ha!), ie: is the RAM base always
at 0x4000?  Is the memory size always limitted to <= 16K?
Is it safe to poke any address, or are there areas
that must be avoided?

Second problem: I need some way to work out whether
dummyrr needs to be set.  Interestingly, leaving this
set for my card causes the machine to spin in dp8390write();
I am writing with "to" == 0x4000 and getting back "crda" == 0x3f00.
I have no idea what it all means, as I have no data sheet/
tech info for this dastardly contraption.