Re: [RFC PATCH 17/27] mtd: nand: ecc: Let the software Hamming ECC engine be unselected

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Boris Brezillon <bbrezillon@kernel.org>
Cc: Mason Yang <masonccyang@mxic.com.tw>, Vignesh R <vigneshr@ti.com>,
	Tudor Ambarus <Tudor.Ambarus@microchip.com>,
	Julien Su <juliensu@mxic.com.tw>,
	Richard Weinberger <richard@nod.at>,
	Schrempf Frieder <frieder.schrempf@kontron.de>,
	Marek Vasut <marek.vasut@gmail.com>,
	linux-mtd@lists.infradead.org,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Brian Norris <computersforpeace@gmail.com>,
	David Woodhouse <dwmw2@infradead.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 17/27] mtd: nand: ecc: Let the software Hamming ECC engine be unselected
Date: Thu, 21 Feb 2019 14:35:39 +0100	[thread overview]
Message-ID: <20190221143539.65035bfa@xps13> (raw)
In-Reply-To: <20190221142002.5a160f87@kernel.org>

Hi Boris,

Boris Brezillon <bbrezillon@kernel.org> wrote on Thu, 21 Feb 2019
14:20:02 +0100:

> On Thu, 21 Feb 2019 13:57:56 +0100
> Miquel Raynal <miquel.raynal@bootlin.com> wrote:
> 
> > There is no reason to always embed the software Hamming ECC engine
> > implementation. By default it is, but we can let the user decide.
> > 
> > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > ---
> >  drivers/mtd/nand/ecc/Kconfig               | 10 +++++-
> >  drivers/mtd/nand/raw/Kconfig               |  2 +-
> >  include/linux/mtd/nand-sw-hamming-engine.h | 38 ++++++++++++++++++++++
> >  3 files changed, 48 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/mtd/nand/ecc/Kconfig b/drivers/mtd/nand/ecc/Kconfig
> > index e0106b3a7ec1..ff20e621ffef 100644
> > --- a/drivers/mtd/nand/ecc/Kconfig
> > +++ b/drivers/mtd/nand/ecc/Kconfig
> > @@ -1,7 +1,15 @@
> >  menu "ECC engine support"
> >  
> >  config MTD_NAND_ECC_SW_HAMMING
> > -	tristate
> > +	tristate "Software Hamming ECC engine"
> > +	default y  
> 
> Same as for the NAND_CORE stuff, let users this option when they need
> it instead of having a "default y". Haven't made my mind yet on whether
> this option should be visible to users or not. I guess it could be with
> the new infrastructure, but it's probably too early in the patch series
> to change that.

This one is different.

Before the series: the software Hamming ECC algorithm is part of the
'NAND package'. There is no way to ignore it, it *will* be part of your
binary (or module).

After the series: I just give the user the possibility to deselect
this option. But having 'default y' is mandatory here to avoid breaking
current defconfigs.

> 
> > +	help
> > +	  This enables support for software Hamming error
> > +	  correction. This correction can correct up to 1 bit error
> > +	  per chunk and detect up to 2 bit errors. While it used to be
> > +	  widely used with old parts, newer NAND chips usually require
> > +	  more strength correction and in this case BCH or RS will be
> > +	  preferred.
> >    

Thanks,
Miquèl

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