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

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

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

> Perl doesn't cover all applications, but it's perfectly adequate in many
> places where you't think only C will do the job, e.g. mknbi which does
> binary manipulations and a streaming video server. It may be a long time
> before we see an Etherboot in Perl though.

I guess my point is mknbi is just at the edge.  And I crossed that
edge with my version and wasn't at all happy about it.  Which is why
I advised caution.
 
> >What is clear is that you can have multiple rom images, with their
> >own rom header on a 512 byte boundary.  What I don't know yet is
> >if the rom scan algorithm supports those images overlapping.
> 
> I don't think the header has any "data offset" fields, the body just
> follows the header.

The structure is:

A.2  PnP Option ROM Header
Offset    Size     Value    Description
-----------------------------------------------------
00h       BYTE     55h       Signature byte 1.
01h       BYTE     AAh       Signature byte 2.
02h       BYTE     Varies    Option ROM length in 512-byte blocks.
03h       4 BYTES  Varies    Initialization entry point.
07h       17 BYTES Varies    Reserved.
18h       WORD     Varies    Offset to PCI data structure.
1Ah       WORD     Varies    Offset to expansion header structure.

So my question is, can we have something like:

PnP option ROM Header size 64K
512 bytes later, PnP option ROM Header size 64K - 512 bytes
512 bytes later, PnP option ROM header size 64K - 1024 bytes.
etc.

And just adjust the pointers to the code approrpiately.

> >If they can overlap it is probably worth doing, without the ability
> >to overlap we can just make certain etherboot rom images are in
> >multiples of 512 bytes and concat rom images together if there are
> >big enough roms.
> 
> That's easy, just concatenate the ROM images. At the moment they aren't
> as small as they could be because they are padded out to the next power
> of 2, but an additional option could allow them to be padded to the next
> block only.

Right concatenation will work, but you probably can't fit very
many of them into the same rom.  Which generally defeats the purpose.

If I have a chance I will see if I can get overlapping ROMs to work,
that way we can list all of the the supported PCI for one ROM image.

Eric