[U-Boot] [PATCH] [nand] Implement nand_extent_skip_bad

[Scott Wood <scottwood@freescale.com>]

On 12/10/2012 09:24:24 AM, Pantelis Antoniou wrote:
> When accessing nand any bad blocks encountered are skipped, with no
> indication about the amount of bad blocks encountered.
> While this is normally fine, when you have to write a large amount
> of data in chunks, you need to account for the skipped amount due
> to the presence of the bad blocks.
> 
> nand_extend_skip_bad() returns the offset where the next access
> should occur.

s/extend/extent/

> 
> Signed-off-by: Pantelis Antoniou <panto@antoniou-consulting.com>
> ---
>  drivers/mtd/nand/nand_util.c | 50  
> ++++++++++++++++++++++++++++++++++++++++++++
>  include/nand.h               |  2 ++
>  2 files changed, 52 insertions(+)
> 
> diff --git a/drivers/mtd/nand/nand_util.c  
> b/drivers/mtd/nand/nand_util.c
> index 2ba0c5e..a25a4cb 100644
> --- a/drivers/mtd/nand/nand_util.c
> +++ b/drivers/mtd/nand/nand_util.c
> @@ -684,6 +684,56 @@ int nand_read_skip_bad(nand_info_t *nand, loff_t  
> offset, size_t *length,
>  	return 0;
>  }
> 
> +/**
> + * nand_extent_skip_bad:
> + *
> + * Find the extent of a chunk, return the offset where it ends
> + * Blocks that are marked bad are skipped and the next block is  
> examined
> + * instead as long as the extend is short enough to fit even after  
> skipping the
> + * bad blocks.
> + *
> + * @param nand NAND device
> + * @param offset offset in flash
> + * @param length extend length
> + * @return next offset in case of success (loff_t)-1 on error
> + */

Would it be better to return this information from existing read/write  
functions -- either instead of or in addition to exporting this  
functionality?

> +loff_t nand_extent_skip_bad(nand_info_t *nand, loff_t offset, size_t  
> length)
> +{
> +	size_t block_len, block_off;
> +	loff_t block_start;
> +
> +	if ((offset & (nand->writesize - 1)) != 0) {
> +		printf ("%s: Attempt to check extend non page aligned  
> data\n",
> +				__func__);
> +		return (loff_t)-1;
> +	}
> +
> +	while (length > 0) {
> +
> +		if (offset >= nand->size) {
> +			printf("%s: offset >= nand->size (%llx >=  
> %llx)\n",
> +					__func__, offset, nand->size);
> +			return (loff_t)-1;
> +		}
> +
> +		block_start = offset & ~(loff_t)(nand->erasesize - 1);
> +		block_off = offset & (nand->erasesize - 1);
> +		block_len = nand->erasesize - block_off;
> +		if (block_len > length)		/* left over */
> +			block_len = length;
> +
> +		if (!nand_block_isbad(nand, block_start))
> +			length -= block_len;
> +		else
> +			debug("%s: bad block at %llx (left %x)\n",
> +					__func__, block_start, length);
> +
> +		offset += block_len;
> +	}
> +
> +	return offset;
> +}

This seems duplicative of check_skip_len().

-Scott