[PATCH v4 1/9] kernel: Document ALIGN macros

[Simon Glass]

Add comments for these macros, so it is clear what they do.

Signed-off-by: Simon Glass <sjg at chromium.org>
---

(no changes since v1)

 include/linux/kernel.h | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 9467edd65ab..e5557257e6f 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -35,9 +35,40 @@
 
 #define REPEAT_BYTE(x)	((~0ul / 0xff) * (x))
 
+/**
+ * Rounds a value up to a given alignment
+ *
+ * Note that @a must be a power of two
+ *
+ * Returns the lowest value >= @x which is a multiple of @a
+ *
+ * For example ALIGN(0x123, 8) == 0x128
+ */
 #define ALIGN(x,a)		__ALIGN_MASK((x),(typeof(x))(a)-1)
+
+/**
+ * Rounds a down to a given alignment
+ *
+ * Note that @a must be a power of two
+ *
+ * Returns the highest value <= @x which is a multiple of @a
+ *
+ * For example ALIGN_DOWN(0x123, 8) == 0x120
+ * ALIGN_DOWN(0x120, 16) == 0x120
+ */
 #define ALIGN_DOWN(x, a)	ALIGN((x) - ((a) - 1), (a))
+
+/**
+ * Rounds a value up to a given alignment-mask
+*
+ * Note that @mask must be one less than a power of two
+ *
+ * Returns the lowest value >= @x where the bits set in @mask are 0
+ *
+ * For example __ALIGN_MASK(0x123, 0xf) == 0x130
+ */
 #define __ALIGN_MASK(x,mask)	(((x)+(mask))&~(mask))
+
 #define PTR_ALIGN(p, a)		((typeof(p))ALIGN((unsigned long)(p), (a)))
 #define IS_ALIGNED(x, a)		(((x) & ((typeof(x))(a) - 1)) == 0)
 
-- 
2.43.0