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

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Date: Fri, 23 Feb 2024 11:07:52 +0100
From: Herve Codina <herve.codina@...tlin.com>
To: Yury Norov <yury.norov@...il.com>, 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>, 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

Andy, Yury,

On Thu, 22 Feb 2024 13:50:48 -0800
Yury Norov <yury.norov@...il.com> wrote:

> 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.
> 

Right, I will keep my last paragraph in the next iteration.

Regards,
Hervé