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Message-ID: <20160310190601.GC2545@google.com>
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>,
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Kukjin Kim <kgene@...nel.org>,
Krzysztof Kozlowski <k.kozlowski@...sung.com>,
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Nicolas Ferre <nicolas.ferre@...el.com>,
Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
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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
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