linux-kernel - [PATCH] lib/scatterlist: mark input buffer parameters as 'const'

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Date:	Tue, 28 Apr 2015 11:45:33 +0100
From:	Dave Gordon <david.s.gordon@...el.com>
To:	linux-kernel@...r.kernel.org
Cc:	Akinobu Mita <akinobu.mita@...il.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Dave Gordon <david.s.gordon@...el.com>
Subject: [PATCH] lib/scatterlist: mark input buffer parameters as 'const'

The 'buf' parameter of sg(p)copy_from_buffer() can and should be
const-qualified, although because of the shared implementation of
_to_buffer() and _from_buffer(), we have to cast this away internally.

This means that callers who have a 'const' buffer containing the data
to be copied to the sg-list no longer have to cast away the const-ness
themselves. It also enables improved coverage by code analysis tools.

Signed-off-by: Dave Gordon <david.s.gordon@...el.com>
---
 include/linux/scatterlist.h |    4 ++--
 lib/scatterlist.c           |    8 ++++----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index ed8f9e7..c90038b 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -240,12 +240,12 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
 	gfp_t gfp_mask);
 
 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
-			   void *buf, size_t buflen);
+			   const void *buf, size_t buflen);
 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 			 void *buf, size_t buflen);
 
 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
-			    void *buf, size_t buflen, off_t skip);
+			    const void *buf, size_t buflen, off_t skip);
 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 			  void *buf, size_t buflen, off_t skip);
 
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index c9f2e8c..9df76c4 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -669,9 +669,9 @@ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
  *
  **/
 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
-			   void *buf, size_t buflen)
+			   const void *buf, size_t buflen)
 {
-	return sg_copy_buffer(sgl, nents, buf, buflen, 0, false);
+	return sg_copy_buffer(sgl, nents, (void *)buf, buflen, 0, false);
 }
 EXPORT_SYMBOL(sg_copy_from_buffer);
 
@@ -704,9 +704,9 @@ EXPORT_SYMBOL(sg_copy_to_buffer);
  *
  **/
 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
-			    void *buf, size_t buflen, off_t skip)
+			    const void *buf, size_t buflen, off_t skip)
 {
-	return sg_copy_buffer(sgl, nents, buf, buflen, skip, false);
+	return sg_copy_buffer(sgl, nents, (void *)buf, buflen, skip, false);
 }
 EXPORT_SYMBOL(sg_pcopy_from_buffer);
 
-- 
1.7.9.5

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