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[PATCH] pinctrl: pinctrl-mtk-common: fix a possible NULL pointer deference

The function, external interrupt controller, is made as an optional to
pinctrl. But if we don't want pio behaves as an external interrupt
controller, it would lead to pctl->eint not be created properly and then
will cause 'kernel NULL pointer' issue when gpiochip try to call .to_irq
or .set_config. To fix it, check pctl->eint before accessing the member.

See commit 5f591543a937 ("pinctrl: mt7622: fix a kernel panic when pio
don't work as EINT controller") for details.

Signed-off-by: Young Xiao <92siuyang@xxxxxxxxx>
 drivers/pinctrl/mediatek/pinctrl-mtk-common.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/pinctrl/mediatek/pinctrl-mtk-common.c b/drivers/pinctrl/mediatek/pinctrl-mtk-common.c
index 0716238..b395f0b 100644
--- a/drivers/pinctrl/mediatek/pinctrl-mtk-common.c
+++ b/drivers/pinctrl/mediatek/pinctrl-mtk-common.c
@@ -836,6 +836,9 @@ static int mtk_gpio_to_irq(struct gpio_chip *chip, unsigned offset)
 	const struct mtk_desc_pin *pin;
 	unsigned long eint_n;
+	if (!pctl->eint)
+		return -ENOTSUPP;
 	pin = pctl->devdata->pins + offset;
 	if (pin->eint.eintnum == NO_EINT_SUPPORT)
 		return -EINVAL;
@@ -853,7 +856,8 @@ static int mtk_gpio_set_config(struct gpio_chip *chip, unsigned offset,
 	unsigned long eint_n;
 	u32 debounce;
-	if (pinconf_to_config_param(config) != PIN_CONFIG_INPUT_DEBOUNCE)
+	if (!pctl->eint ||
+	    pinconf_to_config_param(config) != PIN_CONFIG_INPUT_DEBOUNCE)
 		return -ENOTSUPP;
 	pin = pctl->devdata->pins + offset;