The debugfs_create_dir() function returns ERR_PTR() on error, not NULL.
The current null-check fails to catch errors.

Use IS_ERR() to correctly check for errors.

Fixes: 8ea4484d0c2b ("mailbox: Add generic mechanism for testing Mailbox Controllers")
Signed-off-by: Haotian Zhang <vulab@iscas.ac.cn>
---
 drivers/mailbox/mailbox-test.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mailbox/mailbox-test.c b/drivers/mailbox/mailbox-test.c
index c9dd8c42c0cd..3a28ab5c42e5 100644
--- a/drivers/mailbox/mailbox-test.c
+++ b/drivers/mailbox/mailbox-test.c
@@ -268,7 +268,7 @@ static int mbox_test_add_debugfs(struct platform_device *pdev,
 		return 0;
 
 	tdev->root_debugfs_dir = debugfs_create_dir(dev_name(&pdev->dev), NULL);
-	if (!tdev->root_debugfs_dir) {
+	if (IS_ERR(tdev->root_debugfs_dir)) {
 		dev_err(&pdev->dev, "Failed to create Mailbox debugfs\n");
 		return -EINVAL;
 	}
-- 
2.50.1.windows.1