linux-kernel - Re: [PATCH v4 00/52] mtd: rework ECC layout definition

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Date:	Thu, 10 Mar 2016 11:06:01 -0800
From:	Brian Norris <computersforpeace@...il.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	linux-mtd@...ts.infradead.org, Daniel Mack <daniel@...que.org>,
	Haojian Zhuang <haojian.zhuang@...il.com>,
	Robert Jarzmik <robert.jarzmik@...e.fr>,
	Kukjin Kim <kgene@...nel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	linux-samsung-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Ralf Baechle <ralf@...ux-mips.org>, linux-mips@...ux-mips.org,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Wenyou Yang <wenyou.yang@...el.com>,
	Josh Wu <rainyfeeling@...look.com>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Chen-Yu Tsai <wens@...e.org>, linux-sunxi@...glegroups.com,
	Stefan Agner <stefan@...er.ch>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
	punnaiah choudary kalluri <punnaia@...inx.com>,
	Priit Laes <plaes@...es.org>,
	Kamal Dasu <kdasu.kdev@...il.com>,
	bcm-kernel-feedback-list@...adcom.com, linux-api@...r.kernel.org,
	Harvey Hunt <harvey.hunt@...tec.com>,
	Richard Weinberger <richard@....at>
Subject: Re: [PATCH v4 00/52] mtd: rework ECC layout definition

On Mon, Mar 07, 2016 at 10:46:50AM +0100, Boris Brezillon wrote:
> Hello,
> 
> This patchset aims at getting rid of the nand_ecclayout limitations.
> struct nand_ecclayout is defining fixed eccpos and oobfree arrays which
> can only be increased by modifying the MTD_MAX_ECCPOS_ENTRIES_LARGE and
> MTD_MAX_OOBFREE_ENTRIES_LARGE macros.
> This approach forces us to modify the macro values each time we add a
> new NAND chip with a bigger OOB area, and increasing these arrays also
> penalize all platforms, even those who only support small NAND devices
> (with small OOB area).
> 
> The idea to overcome this limitation, is to define the ECC/OOB layout
> by the mean of two functions: ->ecc() and ->free(), which will
> basically return the same information has those stored in the
> nand_ecclayout struct.
> 
> Another advantage of this solution is that ECC layouts are usually
> following a repetitive pattern (i.e. leave X bytes free and put Y bytes
> of ECC per ECC chunk), which allows one to implement the ->ecc()
> and ->free() functions with a simple logic that can be applied
> to any size of OOB.
> 
> Patches 1 to 4 are just cleanups or trivial fixes that can be taken
> independently.
> 
> Also note that the last two commits are removing the nand_ecclayout
> definition, thus preventing any new driver to use this structure.
> Of course, this step can be delayed if some of the previous patches
> are not accepted.
> 
> All those changes are available here [1].
> 
> Best Regards,
> 
> Boris
> 
> [1]https://github.com/bbrezillon/linux-0day/tree/nand/ecclayout

FYI, I've pushed patches 1-4 to l2-mtd.git. I'll take another look at
them this week I hope (or your new fellow, Richard, can!), then you can
queue them up for the next cycle.

Brian