[PATCH] SG: set names for numeric constants

[Cyrill Gorcunov <gorcunov@gmail.com>]

This patch defines names for numeric constants that
used in scatter list for more convenient code reading.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>

---

I'm not sure if it really needed but who knows ;)
Any comments are welcome.

 include/linux/scatterlist.h |   21 ++++++++++++---------
 1 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 4571231..fcc05a5 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -25,6 +25,9 @@
  */
 
 #define SG_MAGIC	0x87654321
+#define SG_CHAIN	0x1
+#define SG_LAST		0x2
+#define SG_MASK		0x3
 
 /**
  * sg_assign_page - Assign a given page to an SG entry
@@ -38,13 +41,13 @@
  **/
 static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
 {
-	unsigned long page_link = sg->page_link & 0x3;
+	unsigned long page_link = sg->page_link & SG_MASK;
 
 	/*
 	 * In order for the low bit stealing approach to work, pages
 	 * must be aligned at a 32-bit boundary as a minimum.
 	 */
-	BUG_ON((unsigned long) page & 0x03);
+	BUG_ON((unsigned long) page & SG_MASK);
 #ifdef CONFIG_DEBUG_SG
 	BUG_ON(sg->sg_magic != SG_MAGIC);
 #endif
@@ -73,7 +76,7 @@ static inline void sg_set_page(struct scatterlist *sg, struct page *page,
 	sg->length = len;
 }
 
-#define sg_page(sg)	((struct page *) ((sg)->page_link & ~0x3))
+#define sg_page(sg)	((struct page *) ((sg)->page_link & ~SG_MASK))
 
 /**
  * sg_set_buf - Set sg entry to point at given data
@@ -93,10 +96,10 @@ static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
  * a valid sg entry, or whether it points to the start of a new scatterlist.
  * Those low bits are there for everyone! (thanks mason :-)
  */
-#define sg_is_chain(sg)		((sg)->page_link & 0x01)
-#define sg_is_last(sg)		((sg)->page_link & 0x02)
+#define sg_is_chain(sg)		((sg)->page_link & SG_CHAIN)
+#define sg_is_last(sg)		((sg)->page_link & SG_LAST)
 #define sg_chain_ptr(sg)	\
-	((struct scatterlist *) ((sg)->page_link & ~0x03))
+	((struct scatterlist *) ((sg)->page_link & ~SG_MASK))
 
 /**
  * sg_next - return the next scatterlist entry in a list
@@ -179,7 +182,7 @@ static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
 #ifndef ARCH_HAS_SG_CHAIN
 	BUG();
 #endif
-	prv[prv_nents - 1].page_link = (unsigned long) sgl | 0x01;
+	prv[prv_nents - 1].page_link = (unsigned long) sgl | SG_CHAIN;
 }
 
 /**
@@ -193,12 +196,12 @@ static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
  **/
 static inline void sg_mark_end(struct scatterlist *sgl, unsigned int nents)
 {
-	sgl[nents - 1].page_link = 0x02;
+	sgl[nents - 1].page_link = SG_LAST;
 }
 
 static inline void __sg_mark_end(struct scatterlist *sg)
 {
-	sg->page_link |= 0x02;
+	sg->page_link |= SG_LAST;
 }
 
 /**