[tip:x86/asm] bitops: Adjust the comment on get_order() to describe the size==0 case

[tip-bot for David Howells]

Commit-ID:  e0891a9816316b5e05fd5b0453ffe9fd6a56f489
Gitweb:     http://git.kernel.org/tip/e0891a9816316b5e05fd5b0453ffe9fd6a56f489
Author:     David Howells <dhowells@xxxxxxxxxx>
AuthorDate: Mon, 20 Feb 2012 22:39:18 +0000
Committer:  H. Peter Anvin <hpa@xxxxxxxxx>
CommitDate: Mon, 20 Feb 2012 14:46:55 -0800

bitops: Adjust the comment on get_order() to describe the size==0 case

Adjust the comment on get_order() to note that the result of passing a size of
0 results in an undefined value.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/20120220223917.16199.9416.stgit@xxxxxxxxxxxxxxxxxxxxxx
Acked-by: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxx>
---
 include/asm-generic/getorder.h |   23 ++++++++++++++++++++++-
 1 files changed, 22 insertions(+), 1 deletions(-)

diff --git a/include/asm-generic/getorder.h b/include/asm-generic/getorder.h
index 67e7245..76e9687 100644
--- a/include/asm-generic/getorder.h
+++ b/include/asm-generic/getorder.h
@@ -5,7 +5,28 @@
 
 #include <linux/compiler.h>
 
-/* Pure 2^n version of get_order */
+/**
+ * get_order - Determine the allocation order of a memory size
+ * @size: The size for which to get the order
+ *
+ * Determine the allocation order of a particular sized block of memory.  This
+ * is on a logarithmic scale, where:
+ *
+ *	0 -> 2^0 * PAGE_SIZE and below
+ *	1 -> 2^1 * PAGE_SIZE to 2^0 * PAGE_SIZE + 1
+ *	2 -> 2^2 * PAGE_SIZE to 2^1 * PAGE_SIZE + 1
+ *	3 -> 2^3 * PAGE_SIZE to 2^2 * PAGE_SIZE + 1
+ *	4 -> 2^4 * PAGE_SIZE to 2^3 * PAGE_SIZE + 1
+ *	...
+ *
+ * The order returned is used to find the smallest allocation granule required
+ * to hold an object of the specified size.
+ *
+ * The result is undefined if the size is 0.
+ *
+ * This function may be used to initialise variables with compile time
+ * evaluations of constants.
+ */
 static inline __attribute_const__ int get_order(unsigned long size)
 {
 	int order;
--
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