lib: bitmap: add alignment offset for bitmap_find_next_zero_area()

Add a bitmap_find_next_zero_area_off() function which works like
bitmap_find_next_zero_area() function except it allows an offset to be
specified when alignment is checked.  This lets caller request a bit such
that its number plus the offset is aligned according to the mask.

[gregory.0xf0@gmail.com: Retrieved from https://patchwork.linuxtv.org/patch/6254/ and updated documentation]
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Gregory Fong <gregory.0xf0@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Laura Abbott <lauraa@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 31 insertions, 5 deletions

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index e1c8d080c42..34e020c2364 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -45,6 +45,7 @@
  * bitmap_set(dst, pos, nbits)			Set specified bit area
  * bitmap_clear(dst, pos, nbits)		Clear specified bit area
  * bitmap_find_next_zero_area(buf, len, pos, n, mask)	Find bit free area
+ * bitmap_find_next_zero_area_off(buf, len, pos, n, mask)	as above
  * bitmap_shift_right(dst, src, n, nbits)	*dst = *src >> n
  * bitmap_shift_left(dst, src, n, nbits)	*dst = *src << n
  * bitmap_remap(dst, src, old, new, nbits)	*dst = map(old, new)(src)
@@ -114,11 +115,36 @@ extern int __bitmap_weight(const unsigned long *bitmap, unsigned int nbits);
 
 extern void bitmap_set(unsigned long *map, unsigned int start, int len);
 extern void bitmap_clear(unsigned long *map, unsigned int start, int len);
-extern unsigned long bitmap_find_next_zero_area(unsigned long *map,
-					 unsigned long size,
-					 unsigned long start,
-					 unsigned int nr,
-					 unsigned long align_mask);
+
+extern unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
+						    unsigned long size,
+						    unsigned long start,
+						    unsigned int nr,
+						    unsigned long align_mask,
+						    unsigned long align_offset);
+
+/**
+ * bitmap_find_next_zero_area - find a contiguous aligned zero area
+ * @map: The address to base the search on
+ * @size: The bitmap size in bits
+ * @start: The bitnumber to start searching at
+ * @nr: The number of zeroed bits we're looking for
+ * @align_mask: Alignment mask for zero area
+ *
+ * The @align_mask should be one less than a power of 2; the effect is that
+ * the bit offset of all zero areas this function finds is multiples of that
+ * power of 2. A @align_mask of 0 means no alignment is required.
+ */
+static inline unsigned long
+bitmap_find_next_zero_area(unsigned long *map,
+			   unsigned long size,
+			   unsigned long start,
+			   unsigned int nr,
+			   unsigned long align_mask)
+{
+	return bitmap_find_next_zero_area_off(map, size, start, nr,
+					      align_mask, 0);
+}
 
 extern int bitmap_scnprintf(char *buf, unsigned int len,
 			const unsigned long *src, int nbits);