Open Firmware use on OLPC.
wmb at firmworks.com
Fri Oct 13 16:12:33 EDT 2006
Ronald G Minnich wrote:
> Mitch Bradley wrote:
>> We should have the OFW building tools available in a public place
>> within a few weeks. At that point it would be really cool if someone
>> would undertake the conversion to LZMA.
> why not just LZMA the whole image?
That makes it a little smaller but not enough to get below another
boundary (it's already less than 512K with LB + VSA + EC).
OFW has fine-grained gzip. The overall image is a set of concatenated
modules, each of which can be gzip'ed or not. Modules are copied or
decompressed into RAM as needed, e.g. as a result of probing specific
hardware. The gunzipper is also used when loading boot images, which
will be automatically unzipped if necessary. It can also handle .zip
files; that's a convenient format for loading multi-file wads. Finally,
the unzipper is needed for handling the zlib compressed JFFS2 fragments.
> It's running as a single linuxbios payload right?
Yes. But it doesn't all get copied into RAM. The ELF header is set up
so the payload just stays in ROM, and the early startup code
decompresses just the necessary bits into RAM as needed.
> I am hoping we do the buildrom cutover to OFW soon.
I have that working on an internal development machine at OLPC. Jordan
is currently reviewing the way I set it up. I'm sure I made some dumb
mistakes in my ignorance. The OFW payload build takes 5 seconds from
ground zero, including unpacking the tarball.
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