linux-kernel - Re: [PATCH v4 1/4] mtd: nand: provide detailed description for raw read/write page methods

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Message-ID: <20141025035524.GA3579@localhost.localdomain>
Date:	Sat, 25 Oct 2014 11:55:27 +0800
From:	Huang Shijie <shijie8@...il.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Mike Voytovich <mvoytovich@...pal.com>,
	Roy Lee <roylee@...pal.com>
Subject: Re: [PATCH v4 1/4] mtd: nand: provide detailed description for raw
 read/write page methods

On Mon, Oct 20, 2014 at 10:46:14AM +0200, Boris Brezillon wrote:
> read_page_raw and write_page_raw method description is not clear enough.
> It clearly specifies that ECC correction should not be involved but does
> not talk about specific layout (by layout I mean where in-band and
> out-of-band data are stored on the NAND media) used by NAND/ECC
> controllers.
> 
> Those specific layouts might impact MTD users and thus should be hidden (as
> already done in the standard NAND_ECC_HW_SYNDROME implementation).
> 
> Clearly state this constraint in the nand_ecc_ctrl struct documentation.
> 
> Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> ---
>  include/linux/mtd/nand.h | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
> index e4d451e..b14d190 100644
> --- a/include/linux/mtd/nand.h
> +++ b/include/linux/mtd/nand.h
> @@ -455,8 +455,21 @@ struct nand_hw_control {
>   *		be provided if an hardware ECC is available
>   * @calculate:	function for ECC calculation or readback from ECC hardware
>   * @correct:	function for ECC correction, matching to ECC generator (sw/hw)
> - * @read_page_raw:	function to read a raw page without ECC
> - * @write_page_raw:	function to write a raw page without ECC
> + * @read_page_raw:	function to read a raw page without ECC. This function
> + *			should hide the specific layout used by the ECC
> + *			controller and always return contiguous in-band and
> + *			out-of-band data even if they're not stored
> + *			contiguously on the NAND chip (e.g.
> + *			NAND_ECC_HW_SYNDROME interleaves in-band and
> + *			out-of-band data).
> + * @write_page_raw:	function to write a raw page without ECC. This function
> + *			should hide the specific layout used by the ECC
> + *			controller and consider the passed data as contiguous
> + *			in-band and out-of-band data. ECC controller is
> + *			responsible for doing the appropriate transformations
> + *			to adapt to its specific layout (e.g.
> + *			NAND_ECC_HW_SYNDROME interleaves in-band and
> + *			out-of-band data).
>   * @read_page:	function to read a page according to the ECC generator
>   *		requirements; returns maximum number of bitflips corrected in
>   *		any single ECC step, 0 if bitflips uncorrectable, -EIO hw error
> -- 
> 1.9.1
> 
thanks for this patch. 

hi Brian, what's your opinion about this patch?

thanks
Huang Shijie
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