linux-kernel - RE: [patch v4 1/7] crc32: move-to-documentation.diff

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Date:	Tue, 9 Aug 2011 13:52:33 -0500
From:	"Bob Pearson" <rpearson@...temfabricworks.com>
To:	"'Joakim Tjernlund'" <joakim.tjernlund@...nsmode.se>,
	"'George Spelvin'" <linux@...izon.com>
Cc:	<akpm@...ux-foundation.org>, <fzago@...temfabricworks.com>,
	<linux-kernel@...r.kernel.org>, <rdunlap@...otime.net>
Subject: RE: [patch v4 1/7] crc32: move-to-documentation.diff



> -----Original Message-----
> From: Joakim Tjernlund [mailto:joakim.tjernlund@...nsmode.se]
> Sent: Tuesday, August 09, 2011 11:50 AM
> To: George Spelvin
> Cc: akpm@...ux-foundation.org; fzago@...temfabricworks.com; linux-
> kernel@...r.kernel.org; rdunlap@...otime.net;
> rpearson@...temfabricworks.com
> Subject: Re: [patch v4 1/7] crc32: move-to-documentation.diff
> 
> "George Spelvin" <linux@...izon.com> wrote on 2011/08/09 13:45:04:
> >
> > Here's a hopefully-improved Documentation file, which explains the
slicing
> > algorithm as well.  As long as you have a big diff, it seems worth
tweaking.
> >
> > You also might want to leave a pointer in lib/crc32.c to the relocated
docs.
> >
> > (I'm just inclding the whole changed file because I assume it's easier
> > to review that way; do you prefer a diff?)
> 
> Nice, reading this once again I think I found an old typo. See below
> 
> Perhaps Bob can add this addition to his patch series?
> 
> >
> > === Cut here ===
> ...
> > Or in little-endian:
> > for (i = 0; i < input_bytes; i++) {
> >    remainder ^= next_input_byte();
> >    for (j = 0; j < 8; j++) {
> >       multiple = (remainder & 1) ? CRCPOLY : 0;
> >       remainder = (remainder << 1) ^ multiple;
> 
> Should not above line be:
>        remainder = (remainder >> 1) ^ multiple;

I agree. Will change in text.

> ?
> 
> >    }
> > }
> >
> > If the input is a multiple of 32 bits, you can even XOR in a 32-bit
> > word at a time and increase the inner loop count to 32.

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