[PATCH v2] irqchip: mediatek: Use IS_ERR() instead of NULL pointer check

[Yingjoe Chen <yingjoe.chen@mediatek.com>]

Beniamino reported a kernel oops caused by an invalid DT file for the
mediatek interrupt polarity extension.

The reason is that the interrupt polarity support for mediatek chips
merely checks for NULL pointer instead of a casted error return
value in mtk_sysirq_of_init() so any other casted error value passes
the NULL pointer check and causes a kernel panic when dereferenced.

Use IS_ERR() and return the error value via PTR_ERR().

Reported-and-tested-by: Beniamino Galvani <b.galvani@gmail.com>
Signed-off-by: Yingjoe Chen <yingjoe.chen@mediatek.com>
---
 drivers/irqchip/irq-mtk-sysirq.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/irq-mtk-sysirq.c b/drivers/irqchip/irq-mtk-sysirq.c
index 7e342df..0b0d2c0 100644
--- a/drivers/irqchip/irq-mtk-sysirq.c
+++ b/drivers/irqchip/irq-mtk-sysirq.c
@@ -137,9 +137,9 @@ static int __init mtk_sysirq_of_init(struct device_node *node,
 		return -ENOMEM;
 
 	chip_data->intpol_base = of_io_request_and_map(node, 0, "intpol");
-	if (!chip_data->intpol_base) {
+	if (IS_ERR(chip_data->intpol_base)) {
 		pr_err("mtk_sysirq: unable to map sysirq register\n");
-		ret = -ENOMEM;
+		ret = PTR_ERR(chip_data->intpol_base);
 		goto out_free;
 	}
 
-- 
1.8.1.1.dirty