linux-kernel - Re: [RFC PATCH] mtd: add per NAND partition ECC config

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Message-ID: <52FA3225.5010203@gmail.com>
Date:	Tue, 11 Feb 2014 15:22:29 +0100
From:	Boris BREZILLON <b.brezillon.dev@...il.com>
To:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
CC:	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] mtd: add per NAND partition ECC config

Hi Ezequiel,

On 11/02/2014 15:01, Ezequiel Garcia wrote:
> Hi Boris,
>
> On Sat, Feb 08, 2014 at 11:26:46AM +0100, Boris BREZILLON wrote:
>> This patch aims to add per partition ECC config for NAND devices.
>> It defines a new field in the mtd struct to store the mtd ECC config and
>> thus each mtd partition device can store its config instead of using the
>> default NAND chip config.
>>
>> This feature is needed to support the sunxi boot0 paritition case:
>> Allwinner boot code (BROM) requires a specific HW ECC for its boot code
>> that may not fit the HW NAND requirements for the entire NAND chip.
>>
>> Signed-off-by: Boris BREZILLON <b.brezillon.dev@...il.com>
>> ---
>> Hello,
>>
>> This patch is just a draft that implement per partition ECC config.
>> It's currently not properly splitted (it should be separated in several
>> patches) and not documented either.
>>
> Ah, ah...
>
>> There's at least one point that bother me in the current implementation:
>> I introduced DT notions in the nand core code by the mean of the get_ecc_ctrl
>> callback, and so far this was kept out of mtd/nand core code (I guess it was
>> on purpose).
>>
>> Please let me know if you see other drawbacks.
>>
>> If you think per partition ECC should not be implemented, could you help me
>> find a way to handle sunxi specific case decribed above ?
>>
>>   drivers/mtd/mtdpart.c          |   23 ++-
>>   drivers/mtd/nand/nand_base.c   |  428 ++++++++++++++++++++++++----------------
> I really appreciate your effort, but 428 changed lines is a too big and
> intrusive change. I must admit I'm not smart enough to review such patches.
>
> I honestly think you'll have better luck getting feedback if you take the time
> to properly split and document this.
>
> Yeah, it's annoying and time-consuming, but it's globally cheaper for you to
> invest time on making it easier for reviewers and maintainers, than for each
> of us to invest the time deciphering this :-)

Fair enough.

Anyway, this proposal does not work.

If nobody objects to this ECC per partition concept, I'll propose 
something else soon.
And this time I'll make a proper documentation and patch separation ;-).

Best Regards,

Boris

>
> Just my point of view, of course.

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