[PATCH 05/11] lib/igt_aux: add fls helper for bitmaps

[Andrzej Hajda <andrzej.hajda@intel.com>]

There are multiple places where such helper can be useful.

Signed-off-by: Andrzej Hajda <andrzej.hajda@intel.com>
---
 lib/igt_aux.c | 20 ++++++++++++++++++++
 lib/igt_aux.h |  1 +
 2 files changed, 21 insertions(+)

diff --git a/lib/igt_aux.c b/lib/igt_aux.c
index d3280c3514a0..abfd8b0fdbd9 100644
--- a/lib/igt_aux.c
+++ b/lib/igt_aux.c
@@ -2152,3 +2152,23 @@ int igt_bitmap_hweight(void *bitmap, int nbits)
 		ret += igt_hweight(bitmap_get_nbits(p, nbits));
 	return ret;
 }
+
+/**
+ * igt_bitmap_fls: find last set bit in bitmap
+ *
+ * @bitmap: pointer to bitmap
+ * @nbits: number of bits to examine
+ *
+ * Bitmap version of fls.
+ */
+int igt_bitmap_fls(void *bitmap, int nbits)
+{
+	uint64_t *p = bitmap;
+	int n = nbits / BITS_PER_TYPE(*p), r = nbits % BITS_PER_TYPE(*p);
+	uint64_t v = r ? bitmap_get_nbits(p + n, r) : 0;
+
+	while (!v && n)
+		v = p[--n];
+
+	return n * BITS_PER_TYPE(*p) + igt_fls(v);
+}
diff --git a/lib/igt_aux.h b/lib/igt_aux.h
index 885c6b096e49..8ff182384cce 100644
--- a/lib/igt_aux.h
+++ b/lib/igt_aux.h
@@ -353,5 +353,6 @@ void *igt_memdup(const void *ptr, size_t len);
 void igt_wait_and_close(int fence_fd);
 
 int igt_bitmap_hweight(void *bitmap, int nbits);
+int igt_bitmap_fls(void *bitmap, int nbits);
 
 #endif /* IGT_AUX_H */

-- 
2.43.0