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

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Message-ID: <ZdfBuFZ7tf4b+3n8@yury-ThinkPad>
Date: Thu, 22 Feb 2024 13:50:48 -0800
From: Yury Norov <yury.norov@...il.com>
To: Herve Codina <herve.codina@...tlin.com>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	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>,
	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

On Thu, Feb 22, 2024 at 05:49:59PM +0100, Herve Codina wrote:
> 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 you would like - please do! :)
 
> If Yury is ok, I can drop this last paragraph.

The original bitmap_onto() description is 3 times longer, and barely
that descriptive. I'm OK with your working and especially pictures.

Thanks,
Yury