Re: [PATCH 2/13] Add sg helpers for iterating over a scatterlist table

Andrew Morton
2007-05-10T10:40:34Z

On Thu, 10 May 2007 12:21:44 +0200 Jens Axboe <jens.axboe@oracle.com> wrote:

> First step to being able to change the scatterlist setup without
> having to modify drivers (a lot :-)
>
> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
> ---
> include/linux/scatterlist.h | 9 +++++++++
> 1 files changed, 9 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
> index 4efbd9c..c5bffde 100644
> --- a/include/linux/scatterlist.h
> +++ b/include/linux/scatterlist.h
> @@ -20,4 +20,13 @@ static inline void sg_init_one(struct scatterlist *sg, const void *buf,
> sg_set_buf(sg, buf, buflen);
> }
>
> +#define sg_next(sg) ((sg) + 1)
> +#define sg_last(sg, nents) (&(sg[nents - 1]))

Looks a bit underparenthesised.

> +/*
> + * Loop over each sg element, following the pointer to a new list if necessary
> + */
> +#define for_each_sg(sglist, sg, nr, __i) \
> + for (__i = 0, sg = (sglist); __i < nr; __i++, sg = sg_next(sg))
> +

So does this.

I don't see how it "follows the pointer to a new list". All it's doing is
iterating across an array?