Re: [PATCH 2.6.1 -- take two] Add CRC32C chksums to crypto and lib routines
From: Matt Mackall (mpm_at_selenic.com)
Date: 02/03/04
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Date: Tue, 3 Feb 2004 13:27:11 -0600 To: Clay Haapala <chaapala@cisco.com>
On Tue, Feb 03, 2004 at 01:13:48PM -0600, Clay Haapala wrote:
> On Tue, 3 Feb 2004, Matt Mackall uttered the following:
>
> +/*
> + * Haven't generated a big-endian table yet, but the bit-wise version
> + * should at least work.
> + */
> >
> > Big-endian in this context means, of course, the order of the bits in
> > the byte rather than bytes in a word, and as this CRC polynomial was
> > chosen especially for its robustness on noise bursts in little-endian
> > transmission (aka standard serial and network *bit* transmission
> > ordering), I think we should intentionally omit BE support and make
> > note of it.
> >
> Yes, it is about transmission bit-order. Is the crc32 BE code also
> not necessary? Does it deal with how various networking hardware
> and architecture combos present this data?
The crc32_be stuff is used by at least Bluetooth, some of the digital
video stuff, and a couple other random things. I suspect it's mostly
historical accident.
> >> +static inline void crypto_chksum_final(struct crypto_tfm *tfm, u32 *out)
> >> +{
> >> + BUG_ON(crypto_tfm_alg_type(tfm) != CRYPTO_ALG_TYPE_CHKSUM);
> >
> > A lot of these BUG_ONs seem to be overkill. You're not going to get
> > here by someone accidentally misusing the interface. You can only get
> > here by some very willful abuse of the interface or by extremely
> > unlikely fandango on core, neither of which is worth trying to defend
> > against.
>
> That would be a worth changing in a clean-up pass over all of
> crypto, then.
I'll do them if James has no objections. I've got a couple other
crypto bits queued.
-- Matt Mackall : http://www.selenic.com : Linux development and consulting - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
- Previous message: Tomas Zvala: "Re: 2.6.0, cdrom still showing directories after being erased"
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