Re: [Etherboot-developers] NIC file and ROM images

[<ebi...@ln...>]

ke...@us... (Ken Yap) writes:

> >What if you (we) could build a bootrom that knows about ALL
> >pci network chipsets.
> 
> You already can, in theory, just do what Michael Brown did with multi
> driver binaries.
> 
> >It would start with a whole bunch of 512 byte PCI headers.
> >Followed by the main() and other common code,  Then, the 
> >unique routines that each card needs. I don't know how big
> >that is, but it seems pretty small, per chipset.
> 
> Unfortunately it isn't, if you'd written a driver before you'd know
> different.  Each driver can have pretty complicated code and use large
> buffers. See tulip.c for an extreme example. To share the buffers would
> require some kind of dynamic memory allocation. And even then there's
> the memory squeeze, see below.

Although all of the buffers should be in the BSS and not matter,
binary size wise.
 
> >I use 29ee512 chips for the Linksys and 3Com cards, 
> >I'll bet we could fit support for a lot of chipsets into 64k.
> 
> The problem is not the ROM size, but the limited execution area with
> which Etherboot has to work (48kB from 0x94000). Hence the interest in a
> relocatable Etherboot binary which could copy itself to the top of
> memory, which should leave enough room at the bottom for the loaded code
> in all except very memory deficient machines. But that's a promising
> direction to work towards.

And the challenge with a relocateable binary is that we would need
to split etherboot into 2 sections.  The 16bit code section, which
must be under 1M, and the rest.  And we can probably place the
code that must be under 1M between 0xC0000 - 0xE0000, basically
just leave it there as our initialization finishes.

I have the self relocation working just fine with memtest86, reducing
it's memory footprint from 128KB to 56KB because it no longer has to
have 2 copies of itself.  I have a few more hurdles to over come
before I release patches against memtest86 but I have the self
relocating working solidly.

Eric