[PATCH 1/3] mailbox: mailbox-test: handle channel errors consistently

[Wolfram Sang]

mbox_test_request_channel() returns either an ERR_PTR or NULL. The
callers, however, mostly checked for non-NULL which allows for bogus
code paths when an ERR_PTR is treated like a valid channel. A later
commit tried to fix it in one place but missed the other ones. Because
the ERR_PTR is only used for -ENOMEM once and is converted to
-EPROBE_DEFER anyhow, convert the callee to only return NULL which
simplifies handling a lot and makes it less error prone.

Fixes: 8ea4484d0c2b ("mailbox: Add generic mechanism for testing Mailbox Controllers")
Fixes: 9b63a810c6f9 ("mailbox: mailbox-test: Fix an error check in mbox_test_probe()")
Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
---
 drivers/mailbox/mailbox-test.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mailbox/mailbox-test.c b/drivers/mailbox/mailbox-test.c
index 5e68f708205c..daf4b6f27d11 100644
--- a/drivers/mailbox/mailbox-test.c
+++ b/drivers/mailbox/mailbox-test.c
@@ -336,7 +336,7 @@ mbox_test_request_channel(struct platform_device *pdev, const char *name)
 
 	client = devm_kzalloc(&pdev->dev, sizeof(*client), GFP_KERNEL);
 	if (!client)
-		return ERR_PTR(-ENOMEM);
+		return NULL;
 
 	client->dev		= &pdev->dev;
 	client->rx_callback	= mbox_test_receive_message;
@@ -393,7 +393,7 @@ static int mbox_test_probe(struct platform_device *pdev)
 	tdev->tx_channel = mbox_test_request_channel(pdev, "tx");
 	tdev->rx_channel = mbox_test_request_channel(pdev, "rx");
 
-	if (IS_ERR_OR_NULL(tdev->tx_channel) && IS_ERR_OR_NULL(tdev->rx_channel))
+	if (!tdev->tx_channel && !tdev->rx_channel)
 		return -EPROBE_DEFER;
 
 	/* If Rx is not specified but has Rx MMIO, then Rx = Tx */
-- 
2.51.0