On 09/18/2015 07:57 AM, LABBE Corentin wrote:
Some driver use a modified version of sg_nents_for_len with an
additional parameter bool *chained for knowing if the scatterlist is
chained or not.
So, for removing duplicate code, add sg_nents_len_chained in
lib/scatterlist.c
Signed-off-by: LABBE Corentin <clabbe.montjoie@xxxxxxxxx>
---
include/linux/scatterlist.h | 1 +
lib/scatterlist.c | 40 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 41 insertions(+)
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 556ec1e..594cdb0 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -243,6 +243,7 @@ static inline void *sg_virt(struct scatterlist *sg)
int sg_nents(struct scatterlist *sg);
int sg_nents_for_len(struct scatterlist *sg, u64 len);
+int sg_nents_len_chained(struct scatterlist *sg, u64 len, bool *chained);
struct scatterlist *sg_next(struct scatterlist *);
struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
void sg_init_table(struct scatterlist *, unsigned int);
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index bafa993..070e396 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -90,6 +90,46 @@ int sg_nents_for_len(struct scatterlist *sg, u64 len)
EXPORT_SYMBOL(sg_nents_for_len);
/**
+ * sg_nents_len_chained - return total count of entries in scatterlist
+ * needed to satisfy the supplied length
+ * @sg: The scatterlist
+ * @len: The total required length
+ * @chained A pointer where to store if SG is chained or not
+ *
+ * Description:
+ * Determines the number of entries in sg that are required to meet
+ * the supplied length, taking into account chaining as well
+ * If the scatterlist is chained, set *chained to true.
+ *
+ * Returns:
+ * the number of sg entries needed, negative error on failure
+ *
+ **/
+int sg_nents_len_chained(struct scatterlist *sg, u64 len, bool *chained)
+{
+ int nents;
+ u64 total;
+
+ if (chained)
+ *chained = false;
+
+ if (!len)
+ return 0;
+
+ for (nents = 0, total = 0; sg; sg = sg_next(sg)) {
+ nents++;
+ total += sg->length;
+ if (!sg_is_last(sg) && (sg + 1)->length == 0 && chained)
Wouldn't it be better to use the sg_is_chain macro to determine if the
the entry is chained instead of checking the length?
Thanks,
Tom
+ *chained = true;
+ if (total >= len)
+ return nents;
+ }
+
+ return -EINVAL;
+}
+EXPORT_SYMBOL(sg_nents_len_chained);
+
+/**
* sg_last - return the last scatterlist entry in a list
* @sgl: First entry in the scatterlist
* @nents: Number of entries in the scatterlist
--
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