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

On Thu, 10 May 2007 12:21:44 +0200 Jens Axboe <jens.axboe@xxxxxxxxxx> 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@xxxxxxxxxx>
---
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?

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