Re: abuse of nand_correct_data in tmio_nand driver

[vimal singh <vimal.newwork@gmail.com>]

On Wed, Jul 22, 2009 at 8:43 PM, Atsushi Nemoto<anemo@mba.ocn.ne.jp> wrote:
> On Wed, 22 Jul 2009 14:13:30 +0530, vimal singh <vimal.newwork@gmail.com> wrote:
>> >> This can be handled by overriding 'chip->ecc.correct' in driver. You
>> >> may reuse 'nand_correct_data()' code in the driver of 256 byte sector
>> >> ECC.
>> >
>> > Yes, the driver can reuse nand_ecc code to implement its own
>> > nand_correct rountine.
>> >
>> > Or how about adding support for 6byte-ecc/512byte-data to nand_ecc.c
>> > to avoid code duplication?
>> >
>> > I mean something like this.  If it looks acceptable, I will prepare a
>> > patch including similer change to nand_calculate_ecc.
>>
>> I personally do not like any HW specific implementation going into the
>> generic part
>> of the code. This particular issue is specific to your HW, so better
>> handle it in the
>> driver only.
>
> OK, but I still feel duplicating nand_ecc code is not so good.  How
> about splitting nand_correct_data into two parts?  A pure calculation
> function and a wrapper for mtd interface.  Like this:

But I do not see any thing extra, which you achieve from this
wrapper...  Is this a prototype, and you want to handle above scenario
in this wrapper (calling 'nand_correct_data' multiple times based on
something, probably 'ecc.bytes')?

>
> diff --git a/drivers/mtd/nand/nand_ecc.c b/drivers/mtd/nand/nand_ecc.c
> index c0cb87d..3920896 100644
> --- a/drivers/mtd/nand/nand_ecc.c
> +++ b/drivers/mtd/nand/nand_ecc.c
> @@ -425,14 +425,14 @@ EXPORT_SYMBOL(nand_calculate_ecc);
>  *
>  * Detect and correct a 1 bit error for 256/512 byte block
>  */
> -int nand_correct_data(struct mtd_info *mtd, unsigned char *buf,
> -                     unsigned char *read_ecc, unsigned char *calc_ecc)
> +int __nand_correct_data(unsigned char *buf,
> +                       unsigned char *read_ecc, unsigned char *calc_ecc,
> +                       unsigned int eccsize)
>  {
>        unsigned char b0, b1, b2, bit_addr;
>        unsigned int byte_addr;
>        /* 256 or 512 bytes/ecc  */
> -       const uint32_t eccsize_mult =
> -                       (((struct nand_chip *)mtd->priv)->ecc.size) >> 8;
> +       const uint32_t eccsize_mult = eccsize >> 8;
>
>        /*
>         * b0 to b2 indicate which bit is faulty (if any)
> @@ -495,6 +495,16 @@ int nand_correct_data(struct mtd_info *mtd, unsigned char *buf,
>        printk(KERN_ERR "uncorrectable error : ");
>        return -1;
>  }
> +EXPORT_SYMBOL(__nand_correct_data);
> +
> +int nand_correct_data(struct mtd_info *mtd, unsigned char *buf,
> +                     unsigned char *read_ecc, unsigned char *calc_ecc)
> +{
> +       const uint32_t eccsize_mult =
> +                       (((struct nand_chip *)mtd->priv)->ecc.size) >> 8;
> +       return __nand_correct_data(buf, read_ecc, calc_ecc,
> +                                  ((struct nand_chip *)mtd->priv)->ecc.size);
> +}
>  EXPORT_SYMBOL(nand_correct_data);
>
>  MODULE_LICENSE("GPL");
>
>
> There is a little bonus: the STANDALONE macro in nand_ecc.c can be
> more useful with this change ;)
>
> ---
> Atsushi Nemoto
>



-- 
---
Regards,
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