diff --git a/drivers/mailbox/mailbox-test.c b/drivers/mailbox/mailbox-test.c
index dc11bbf27274..58d04726cdd7 100644
--- a/drivers/mailbox/mailbox-test.c
+++ b/drivers/mailbox/mailbox-test.c
@@ -46,7 +46,6 @@ static ssize_t mbox_test_signal_write(struct file *filp,
 				       size_t count, loff_t *ppos)
 {
 	struct mbox_test_device *tdev = filp->private_data;
-	int ret;
 
 	if (!tdev->tx_channel) {
 		dev_err(tdev->dev, "Channel cannot do Tx\n");
@@ -60,17 +59,20 @@ static ssize_t mbox_test_signal_write(struct file *filp,
 		return -EINVAL;
 	}
 
-	tdev->signal = kzalloc(MBOX_MAX_SIG_LEN, GFP_KERNEL);
-	if (!tdev->signal)
-		return -ENOMEM;
+	/* Only allocate memory if we need to */
+	if (!tdev->signal) {
+		tdev->signal = kzalloc(MBOX_MAX_SIG_LEN, GFP_KERNEL);
+		if (!tdev->signal)
+			return -ENOMEM;
+	}
 
-	ret = copy_from_user(tdev->signal, userbuf, count);
-	if (ret) {
+	if (copy_from_user(tdev->signal, userbuf, count)) {
 		kfree(tdev->signal);
+		tdev->signal = NULL;
 		return -EFAULT;
 	}
 
-	return ret < 0 ? ret : count;
+	return count;
 }
 
 static const struct file_operations mbox_test_signal_ops = {
diff --git a/drivers/mailbox/mailbox-xgene-slimpro.c b/drivers/mailbox/mailbox-xgene-slimpro.c
index bd07f39f0692..dd2afbca51c9 100644
--- a/drivers/mailbox/mailbox-xgene-slimpro.c
+++ b/drivers/mailbox/mailbox-xgene-slimpro.c
@@ -189,8 +189,8 @@ static int slimpro_mbox_probe(struct platform_device *pdev)
 	int i;
 
 	ctx = devm_kzalloc(&pdev->dev, sizeof(struct slimpro_mbox), GFP_KERNEL);
-	if (IS_ERR(ctx))
-		return PTR_ERR(ctx);
+	if (!ctx)
+		return -ENOMEM;
 
 	platform_set_drvdata(pdev, ctx);
 
diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
index 6a4811f85705..4a36632c236f 100644
--- a/drivers/mailbox/mailbox.c
+++ b/drivers/mailbox/mailbox.c
@@ -375,13 +375,13 @@ struct mbox_chan *mbox_request_channel_byname(struct mbox_client *cl,
 
 	if (!np) {
 		dev_err(cl->dev, "%s() currently only supports DT\n", __func__);
-		return ERR_PTR(-ENOSYS);
+		return ERR_PTR(-EINVAL);
 	}
 
 	if (!of_get_property(np, "mbox-names", NULL)) {
 		dev_err(cl->dev,
 			"%s() requires an \"mbox-names\" property\n", __func__);
-		return ERR_PTR(-ENOSYS);
+		return ERR_PTR(-EINVAL);
 	}
 
 	of_property_for_each_string(np, "mbox-names", prop, mbox_name) {