linux-kernel - [PATCH 1/2] Adjust the comment on get_order() to describe the size==0 case

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Message-ID: <20120220223917.16199.9416.stgit@warthog.procyon.org.uk>
Date:	Mon, 20 Feb 2012 22:39:18 +0000
From:	David Howells <dhowells@...hat.com>
To:	hpa@...or.com
Cc:	x86@...nel.org, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>,
	Arnd Bergmann <arnd@...db.de>
Subject: [PATCH 1/2] 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@...hat.com>
Acked-by: Arnd Bergmann <arnd@...db.de>
---

 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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