lib/bitmap: Introduce bitmap_scatter() and bitmap_gather() helpers

These helpers scatters or gathers a bitmap with the help of the mask
position bits parameter.

bitmap_scatter() does the following:
  src:  0000000001011010
                  ||||||
           +------+|||||
           |  +----+||||
           |  |+----+|||
           |  ||   +-+||
           |  ||   |  ||
  mask: ...v..vv...v..vv
        ...0..11...0..10
  dst:  0000001100000010

and bitmap_gather() performs this one:
   mask: ...v..vv...v..vv
   src:  0000001100000010
            ^  ^^   ^   0
            |  ||   |  10
            |  ||   > 010
            |  |+--> 1010
            |  +--> 11010
            +----> 011010
   dst:  0000000000011010

bitmap_gather() can the seen as the reverse bitmap_scatter() operation.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/lkml/20230926052007.3917389-3-andriy.shevchenko@linux.intel.com/
Co-developed-by: Herve Codina <herve.codina@bootlin.com>
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Acked-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 42 insertions, 0 deletions

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 65f22c2578b0..6b2b33579f56 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -380,6 +380,47 @@ static void __init test_replace(void)
 	expect_eq_bitmap(bmap, exp3_1_0, nbits);
 }
 
+static const unsigned long sg_mask[] __initconst = {
+	BITMAP_FROM_U64(0x000000000000035aULL),
+};
+
+static const unsigned long sg_src[] __initconst = {
+	BITMAP_FROM_U64(0x0000000000000667ULL),
+};
+
+static const unsigned long sg_gather_exp[] __initconst = {
+	BITMAP_FROM_U64(0x0000000000000029ULL),
+};
+
+static const unsigned long sg_scatter_exp[] __initconst = {
+	BITMAP_FROM_U64(0x000000000000021aULL),
+};
+
+static void __init test_bitmap_sg(void)
+{
+	unsigned int nbits = 64;
+	DECLARE_BITMAP(bmap_gather, 100);
+	DECLARE_BITMAP(bmap_scatter, 100);
+	DECLARE_BITMAP(bmap_tmp, 100);
+	DECLARE_BITMAP(bmap_res, 100);
+
+	/* Simple gather call */
+	bitmap_zero(bmap_gather, 100);
+	bitmap_gather(bmap_gather, sg_src, sg_mask, nbits);
+	expect_eq_bitmap(sg_gather_exp, bmap_gather, nbits);
+
+	/* Simple scatter call */
+	bitmap_zero(bmap_scatter, 100);
+	bitmap_scatter(bmap_scatter, sg_src, sg_mask, nbits);
+	expect_eq_bitmap(sg_scatter_exp, bmap_scatter, nbits);
+
+	/* Scatter/gather relationship */
+	bitmap_zero(bmap_tmp, 100);
+	bitmap_gather(bmap_tmp, bmap_scatter, sg_mask, nbits);
+	bitmap_scatter(bmap_res, bmap_tmp, sg_mask, nbits);
+	expect_eq_bitmap(bmap_scatter, bmap_res, nbits);
+}
+
 #define PARSE_TIME	0x1
 #define NO_LEN		0x2
 
@@ -1252,6 +1293,7 @@ static void __init selftest(void)
 	test_copy();
 	test_bitmap_region();
 	test_replace();
+	test_bitmap_sg();
 	test_bitmap_arr32();
 	test_bitmap_arr64();
 	test_bitmap_parse();