[coreboot] Geode LX/CS5536 VSA

Carl-Daniel Hailfinger c-d.hailfinger.devel.2006 at gmx.net
Fri Feb 8 21:05:49 CET 2008

On 08.02.2008 17:21, Chris Kilgour wrote:
> Carl-Daniel Hailfinger wrote:
>>> Please be aware this is all completely untested; there could be plenty
>>> of typos and plain-old mistakes inside.  The binaries produced should be
>>> considered unstable and experimental.  Use them at your own risk!
>> I will try to take a look ASAP. The optimal case would be that the
>> original and modified sources compile to an identical binary or at least
>> a binary with perfectly explainable differences.
> The VSA sources are a mix of assembly and C code.  The binaries will be
> quite different because (naturally) gcc will produce different machine
> code than Microsoft C from the 16-bit era, and all the assembly-coded
> functions are now using GNU __attribute__((fastcall)) rather than "MS
> pascal" calling convention.  Also, the final link output will have the
> various bits and pieces in different locations.  So a straight binary
> diff will exhibit mostly differences.


> That said, I took the time of locating and disassembling the assembly
> functions from OLPC VSA blob and comparing against the output of the
> assembly functions from my build (by far the biggest risk because of all
> the manual modifications I made), and the differences were all
> explainable in light of the above.  For the C code I felt it was way too
> hard to even attempt such an approach.

Thanks for investing the time to verify the differences.

> Within the tarball there is a file modification_notes.txt that
> highlights what I have done.  I'm hoping to foster some discussion on a
> testing approach that lays somewhere between manual inspection and
> slapping the open-tools blob into a coreboot ROM and crossing our fingers...

I fear that for most of us the only way to test is to burn the generated
VSA into a ROM and start the machine. However, I have to admit I didn't
read the modification notes you supplied. I will read it.


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