Messages in this thread | | | Date | Mon, 28 Nov 2011 08:56:33 +0100 | From | Lars-Peter Clausen <> | Subject | Re: [PATCH 2/8] firmware: Sigma: Skip header during CRC generation |
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On 11/25/2011 09:00 PM, Mike Frysinger wrote: > On Friday 25 November 2011 03:55:42 Lars-Peter Clausen wrote: >> On 11/24/2011 06:21 PM, Mike Frysinger wrote: >>> On Thursday 24 November 2011 07:48:21 Lars-Peter Clausen wrote: >>>> The firmware header is not part of the CRC, so skip it. Otherwise the >>>> firmware will be rejected due to non-matching CRCs. >>> >>> that's because you didn't compare to the right value ;). include the CRC >>> -> compare to 0. omit the CRC -> compare to the CRC value. >> >> Does this really work if the CRC is inserted somewhere in the middle of the >> bytestream? > > i don't think the position matters to the CRC algorithm used by sigmadsp. > math principle: a ^ b ^ c is the same thing as b ^ a ^ c and c ^ b ^ a.
If CRC algorithms were commutative they would be pretty weak, I guess ;) > > i could be wrong as to the CRC algo used though. simple enough for you to > check -- i implemented this firmware code based on a spec i wrote up for the > sigmadsp peeps; i never actually had real firmware to test with. > -mike
It does not work.
- Lars
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