irqchip/mbigen: Unify the error handling in mbigen_of_create_domain()

Dan Carpenter reported that commit fea087fc291b "irqchip/mbigen: move
to use bus_get_dev_root()" leads to the following Smatch static checker
warning:

	drivers/irqchip/irq-mbigen.c:258 mbigen_of_create_domain()
	error: potentially dereferencing uninitialized 'child'.

It should not cause a problem on real hardware, but better to fix the
warning, let's move the bus_get_dev_root() out of the loop, and unify
the error handling to silence it.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230505090654.12793-1-wangkefeng.wang@huawei.com

diff --git a/drivers/irqchip/irq-mbigen.c b/drivers/irqchip/irq-mbigen.c
index eada5e0e3eb956c939be7d6eef06e1a0a4aedd39..5101a3fb11df5bef53122db9db3c194669d754e7 100644 (file)
--- a/drivers/irqchip/irq-mbigen.c
+++ b/drivers/irqchip/irq-mbigen.c
@@ -240,26 +240,27 @@ static int mbigen_of_create_domain(struct platform_device *pdev,
        struct irq_domain *domain;
        struct device_node *np;
        u32 num_pins;
+       int ret = 0;
+
+       parent = bus_get_dev_root(&platform_bus_type);
+       if (!parent)
+               return -ENODEV;
 
        for_each_child_of_node(pdev->dev.of_node, np) {
                if (!of_property_read_bool(np, "interrupt-controller"))
                        continue;
 
-               parent = bus_get_dev_root(&platform_bus_type);
-               if (parent) {
-                       child = of_platform_device_create(np, NULL, parent);
-                       put_device(parent);
-                       if (!child) {
-                               of_node_put(np);
-                               return -ENOMEM;
-                       }
+               child = of_platform_device_create(np, NULL, parent);
+               if (!child) {
+                       ret = -ENOMEM;
+                       break;
                }
 
                if (of_property_read_u32(child->dev.of_node, "num-pins",
                                         &num_pins) < 0) {
                        dev_err(&pdev->dev, "No num-pins property\n");
-                       of_node_put(np);
-                       return -EINVAL;
+                       ret = -EINVAL;
+                       break;
                }
 
                domain = platform_msi_create_device_domain(&child->dev, num_pins,
@@ -267,12 +268,16 @@ static int mbigen_of_create_domain(struct platform_device *pdev,
                                                           &mbigen_domain_ops,
                                                           mgn_chip);
                if (!domain) {
-                       of_node_put(np);
-                       return -ENOMEM;
+                       ret = -ENOMEM;
+                       break;
                }
        }
 
-       return 0;
+       put_device(parent);
+       if (ret)
+               of_node_put(np);
+
+       return ret;
 }
 
 #ifdef CONFIG_ACPI