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author | Tomi Valkeinen <tomi.valkeinen@ti.com> | 2012-09-03 09:26:33 +0300 |
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committer | Tomi Valkeinen <tomi.valkeinen@ti.com> | 2012-09-03 09:26:33 +0300 |
commit | c50e86ce7c2961a41f2f7aa6e4fd6c99229ba205 (patch) | |
tree | 4ea36009719bd8fc523239fe1bdccb90f0dce3ae /lib/memweight.c | |
parent | 14d33d384693eb6083396199de516fdef320f7af (diff) | |
parent | 4cbe5a555fa58a79b6ecbb6c531b8bab0650778d (diff) |
Merge tag 'v3.6-rc4'
Merge 3.6-rc4 to get latest OMAP and device tree fixes.
Diffstat (limited to 'lib/memweight.c')
-rw-r--r-- | lib/memweight.c | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/lib/memweight.c b/lib/memweight.c new file mode 100644 index 00000000000..e35fc877189 --- /dev/null +++ b/lib/memweight.c @@ -0,0 +1,38 @@ +#include <linux/export.h> +#include <linux/bug.h> +#include <linux/bitmap.h> + +/** + * memweight - count the total number of bits set in memory area + * @ptr: pointer to the start of the area + * @bytes: the size of the area + */ +size_t memweight(const void *ptr, size_t bytes) +{ + size_t ret = 0; + size_t longs; + const unsigned char *bitmap = ptr; + + for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long); + bytes--, bitmap++) + ret += hweight8(*bitmap); + + longs = bytes / sizeof(long); + if (longs) { + BUG_ON(longs >= INT_MAX / BITS_PER_LONG); + ret += bitmap_weight((unsigned long *)bitmap, + longs * BITS_PER_LONG); + bytes -= longs * sizeof(long); + bitmap += longs * sizeof(long); + } + /* + * The reason that this last loop is distinct from the preceding + * bitmap_weight() call is to compute 1-bits in the last region smaller + * than sizeof(long) properly on big-endian systems. + */ + for (; bytes > 0; bytes--, bitmap++) + ret += hweight8(*bitmap); + + return ret; +} +EXPORT_SYMBOL(memweight); |