linux-kernel - Re: [PATCH v4 3/5] lib/bitmap: Introduce bitmap_scatter() and bitmap

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Message-ID: <20240222174959.7097c29b@bootlin.com>
Date: Thu, 22 Feb 2024 17:49:59 +0100
From: Herve Codina <herve.codina@...tlin.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Vadim Fedorenko <vadim.fedorenko@...ux.dev>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Yury Norov
 <yury.norov@...il.com>, Rasmus Villemoes <linux@...musvillemoes.dk>,
 linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, Andrew Lunn <andrew@...n.ch>, Mark Brown
 <broonie@...nel.org>, Christophe Leroy <christophe.leroy@...roup.eu>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v4 3/5] lib/bitmap: Introduce bitmap_scatter() and
 bitmap_gather() helpers

Hi Andy, Yury,

On Thu, 22 Feb 2024 17:39:27 +0200
Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

..
> > + * bitmap_scatter() for the bitmap scatter detailed operations).  
> 
> > + * Suppose scattered computed using bitmap_scatter(scattered, src, mask, n).
> > + * The operation bitmap_gather(result, scattered, mask, n) leads to a result
> > + * equal or equivalent to src.  
> 
> This paragraph...
> 
> > + * The result can be 'equivalent' because bitmap_scatter() and bitmap_gather()
> > + * are not bijective.  
> 
> 
> > + * The result and src values are equivalent in that sense that a call to
> > + * bitmap_scatter(res, src, mask, n) and a call to bitmap_scatter(res, result,
> > + * mask, n) will lead to the same res value.  
> 
> ...seems duplicating this one.
> 
> I would drop the latter one.

I would like to give details about the 'equivalent' in this scatter/gather case.

If Yury is ok, I can drop this last paragraph.

Thanks for the review,

Regards,
Hervé