lib/bitmap: introduce bitmap_replace() helper

In some drivers we want to have a single operation over bitmap which is
an equivalent to:

	*dst = (*old & ~(*mask)) | (*new & *mask)

Introduce bitmap_replace() helper for this.

Link: http://lkml.kernel.org/r/20191022172922.61232-8-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: William Breathitt Gray <vilhelm.gray@gmail.com>
Cc: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 50 insertions, 0 deletions

diff --git a/lib/bitmap.c b/lib/bitmap.c
index f9e834841e94..4250519d7d1c 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -222,6 +222,18 @@ int __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
 }
 EXPORT_SYMBOL(__bitmap_andnot);
 
+void __bitmap_replace(unsigned long *dst,
+		      const unsigned long *old, const unsigned long *new,
+		      const unsigned long *mask, unsigned int nbits)
+{
+	unsigned int k;
+	unsigned int nr = BITS_TO_LONGS(nbits);
+
+	for (k = 0; k < nr; k++)
+		dst[k] = (old[k] & ~mask[k]) | (new[k] & mask[k]);
+}
+EXPORT_SYMBOL(__bitmap_replace);
+
 int __bitmap_intersects(const unsigned long *bitmap1,
 			const unsigned long *bitmap2, unsigned int bits)
 {
diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 4544847cf81e..e14a15ac250b 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -42,6 +42,19 @@ static const unsigned long exp2[] __initconst = {
 	BITMAP_FROM_U64(0xffffffff77777777ULL),
 };
 
+/* Fibonacci sequence */
+static const unsigned long exp2_to_exp3_mask[] __initconst = {
+	BITMAP_FROM_U64(0x008000020020212eULL),
+};
+/* exp3_0_1 = (exp2[0] & ~exp2_to_exp3_mask) | (exp2[1] & exp2_to_exp3_mask) */
+static const unsigned long exp3_0_1[] __initconst = {
+	BITMAP_FROM_U64(0x33b3333311313137ULL),
+};
+/* exp3_1_0 = (exp2[1] & ~exp2_to_exp3_mask) | (exp2[0] & exp2_to_exp3_mask) */
+static const unsigned long exp3_1_0[] __initconst = {
+	BITMAP_FROM_U64(0xff7fffff77575751ULL),
+};
+
 static bool __init
 __check_eq_uint(const char *srcfile, unsigned int line,
 		const unsigned int exp_uint, unsigned int x)
@@ -257,6 +270,30 @@ static void __init test_copy(void)
 	expect_eq_pbl("0-108,128-1023", bmap2, 1024);
 }
 
+#define EXP2_IN_BITS	(sizeof(exp2) * 8)
+
+static void __init test_replace(void)
+{
+	unsigned int nbits = 64;
+	DECLARE_BITMAP(bmap, 1024);
+
+	bitmap_zero(bmap, 1024);
+	bitmap_replace(bmap, &exp2[0], &exp2[1], exp2_to_exp3_mask, nbits);
+	expect_eq_bitmap(bmap, exp3_0_1, nbits);
+
+	bitmap_zero(bmap, 1024);
+	bitmap_replace(bmap, &exp2[1], &exp2[0], exp2_to_exp3_mask, nbits);
+	expect_eq_bitmap(bmap, exp3_1_0, nbits);
+
+	bitmap_fill(bmap, 1024);
+	bitmap_replace(bmap, &exp2[0], &exp2[1], exp2_to_exp3_mask, nbits);
+	expect_eq_bitmap(bmap, exp3_0_1, nbits);
+
+	bitmap_fill(bmap, 1024);
+	bitmap_replace(bmap, &exp2[1], &exp2[0], exp2_to_exp3_mask, nbits);
+	expect_eq_bitmap(bmap, exp3_1_0, nbits);
+}
+
 #define PARSE_TIME 0x1
 
 struct test_bitmap_parselist{
@@ -476,6 +513,7 @@ static void __init selftest(void)
 	test_zero_clear();
 	test_fill_set();
 	test_copy();
+	test_replace();
 	test_bitmap_arr32();
 	test_bitmap_parselist();
 	test_bitmap_parselist_user();