linux-kernel - Re: [PATCH V3 6/9] mtd: add a new field for ecc info in the nand_flash

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Date:	Wed, 24 Apr 2013 23:57:57 -0700
From:	Brian Norris <computersforpeace@...il.com>
To:	Huang Shijie <b32955@...escale.com>
Cc:	dwmw2@...radead.org, dedekind1@...il.com,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 6/9] mtd: add a new field for ecc info in the nand_flash_dev{}

Last nitpicks for v3 :)

On Tue, Apr 23, 2013 at 1:54 AM, Huang Shijie <b32955@...escale.com> wrote:
> Add the @ecc_info in the nand_flash_dev{}.
> The lower 16 bits are used to store the ECC bits, while the upper 16 bits
> are used to store the ECC data chunk size.

A bit late on this one, but is there a good reason this wasn't just 2
separate 16-bit fields? We already have a few, and I don't see why
this couldn't be the same.

> Signed-off-by: Huang Shijie <b32955@...escale.com>
> ---
>  include/linux/mtd/nand.h |   10 ++++++++++
>  1 files changed, 10 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
> index 063e517..f4c7777 100644
> --- a/include/linux/mtd/nand.h
> +++ b/include/linux/mtd/nand.h
> @@ -624,6 +624,10 @@ struct nand_chip {
>         { .name = (nm), {{ .dev_id = (devid) }}, .chipsize = (chipsz), \
>           .options = (opts) }
>
> +#define NAND_ECC_INFO(strength, size)  (((strength) << 16) | (size))

We could redefine this:

#define NAND_ECC_INFO(strength, size) .ecc_strength = (strength),
.ecc_size = (size)

> +#define NAND_ECC_STRENGTH(x)           (((x) >> 16) & 0xffff)
> +#define NAND_ECC_SIZE(x)               ((x) & 0xffff)

Then we could just drop these unpacking macros.

>  /**
>   * struct nand_flash_dev - NAND Flash Device ID Structure
>   * @name: a human-readable name of the NAND chip
> @@ -641,6 +645,11 @@ struct nand_chip {
>   * @options: stores various chip bit options
>   * @id_len: The valid length of the @id.
>   * @oobsize: OOB size
> + * @ecc_info: The ECC information.
> + *            lower 16 bits: store the ECC bits.
> + *            upper 16 bits: store the ECC data chunk size.
> + *            For example, the "4bit ECC for each 512Byte" can be set with
> + *            NAND_ECC_INFO(4, 512) macro.
>   */
>  struct nand_flash_dev {
>         char *name;
> @@ -657,6 +666,7 @@ struct nand_flash_dev {
>         unsigned int options;
>         uint16_t id_len;
>         uint16_t oobsize;
> +       uint32_t ecc_info;

This could be split to:

uint16_t ecc_strength;
uint16_t ecc_size;

>  };
>
>  /**

Brian
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