lib: sbi_bitmap_test: add tests for bitmap_empty()

Add tests for bitmap_empty(), covers empty/non-empty bitmaps and
edge case nbits=0.

Signed-off-by: Yu-Chien Peter Lin <peter.lin@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260311125116.1401002-2-peter.lin@sifive.com
Signed-off-by: Anup Patel <anup@brainfault.org>

lib/sbi/tests/sbi_bitmap_test.c

diff --git a/lib/sbi/tests/sbi_bitmap_test.c b/lib/sbi/tests/sbi_bitmap_test.c
index d2c3599..b6586fe 100644
--- a/lib/sbi/tests/sbi_bitmap_test.c
+++ b/lib/sbi/tests/sbi_bitmap_test.c
@@ -92,10 +92,39 @@
 	SBIUNIT_EXPECT_MEMEQ(test, res, data_zero, DATA_SIZE);
 }
 
+static void bitmap_empty_test(struct sbiunit_test_case *test)
+{
+	unsigned long res[DATA_SIZE];
+
+	/* All zeros = empty */
+	SBIUNIT_EXPECT_EQ(test, bitmap_empty(data_zero, DATA_BIT_SIZE), true);
+
+	/* Non-zero data = not empty */
+	SBIUNIT_EXPECT_EQ(test, bitmap_empty(data_a, DATA_BIT_SIZE), false);
+	SBIUNIT_EXPECT_EQ(test, bitmap_empty(data_b, DATA_BIT_SIZE), false);
+
+	/* bitmap_zero creates empty bitmap */
+	bitmap_zero(res, DATA_BIT_SIZE);
+	SBIUNIT_EXPECT_EQ(test, bitmap_empty(res, DATA_BIT_SIZE), true);
+
+	/* bitmap_fill creates non-empty bitmap */
+	bitmap_fill(res, DATA_BIT_SIZE);
+	SBIUNIT_EXPECT_EQ(test, bitmap_empty(res, DATA_BIT_SIZE), false);
+
+	/* Single bit set = not empty */
+	bitmap_zero(res, DATA_BIT_SIZE);
+	bitmap_set(res, 0, 1);
+	SBIUNIT_EXPECT_EQ(test, bitmap_empty(res, DATA_BIT_SIZE), false);
+
+	/* Zero nbits = empty */
+	SBIUNIT_EXPECT_EQ(test, bitmap_empty(data_a, 0), true);
+}
+
 static struct sbiunit_test_case bitmap_test_cases[] = {
 	SBIUNIT_TEST_CASE(bitmap_and_test),
 	SBIUNIT_TEST_CASE(bitmap_or_test),
 	SBIUNIT_TEST_CASE(bitmap_xor_test),
+	SBIUNIT_TEST_CASE(bitmap_empty_test),
 	SBIUNIT_END_CASE,
 };