Add comments for these macros, so it is clear what they do.
Signed-off-by: Simon Glass sjg@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)