[PATCH] dma-buf/test: add KUnit case for dma_fence_dedup_array() empty input

[Baineng Shou]

Add a KUnit case verifying that dma_fence_dedup_array() returns 0,
not 1, when called with num_fences == 0. This locks down the
contract documented in the kernel-doc and prevents a regression
of commit 77a9298741f8 ("dma-fence: Make dma_fence_dedup_array()
robust against 0-count input").

Suggested-by: Christian König <christian.koenig@xxxxxxx>
Signed-off-by: Baineng Shou <shoubaineng@xxxxxxxxx>
---
 drivers/dma-buf/st-dma-fence-unwrap.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/dma-buf/st-dma-fence-unwrap.c b/drivers/dma-buf/st-dma-fence-unwrap.c
index 4e7ee25372ba..72dea6091d58 100644
--- a/drivers/dma-buf/st-dma-fence-unwrap.c
+++ b/drivers/dma-buf/st-dma-fence-unwrap.c
@@ -370,6 +370,15 @@ static void test_unwrap_merge_seqno(struct kunit *test)
 	dma_fence_put(f1);
 }
 
+static void test_dedup_empty(struct kunit *test)
+{
+	struct dma_fence *fence[1] = { NULL };
+	int ret;
+
+	ret = dma_fence_dedup_array(fence, 0);
+	KUNIT_EXPECT_EQ(test, ret, 0);
+}
+
 static void test_unwrap_merge_order(struct kunit *test)
 {
 	struct dma_fence *fence, *f1, *f2, *a1, *a2, *c1, *c2;
@@ -595,6 +604,7 @@ static struct kunit_case dma_fence_unwrap_cases[] = {
 	KUNIT_CASE(test_unwrap_merge_order),
 	KUNIT_CASE(test_unwrap_merge_complex),
 	KUNIT_CASE(test_unwrap_merge_complex_seqno),
+	KUNIT_CASE(test_dedup_empty),
 	{}
 };
 
-- 
2.34.1