Merge tag 'v4.15-rc1' into drm-misc-fixes
[platform/kernel/linux-rpi.git] / lib / memweight.c
1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/export.h>
3 #include <linux/bug.h>
4 #include <linux/bitmap.h>
5
6 /**
7  * memweight - count the total number of bits set in memory area
8  * @ptr: pointer to the start of the area
9  * @bytes: the size of the area
10  */
11 size_t memweight(const void *ptr, size_t bytes)
12 {
13         size_t ret = 0;
14         size_t longs;
15         const unsigned char *bitmap = ptr;
16
17         for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long);
18                         bytes--, bitmap++)
19                 ret += hweight8(*bitmap);
20
21         longs = bytes / sizeof(long);
22         if (longs) {
23                 BUG_ON(longs >= INT_MAX / BITS_PER_LONG);
24                 ret += bitmap_weight((unsigned long *)bitmap,
25                                 longs * BITS_PER_LONG);
26                 bytes -= longs * sizeof(long);
27                 bitmap += longs * sizeof(long);
28         }
29         /*
30          * The reason that this last loop is distinct from the preceding
31          * bitmap_weight() call is to compute 1-bits in the last region smaller
32          * than sizeof(long) properly on big-endian systems.
33          */
34         for (; bytes > 0; bytes--, bitmap++)
35                 ret += hweight8(*bitmap);
36
37         return ret;
38 }
39 EXPORT_SYMBOL(memweight);