[PATCH 2/3] gpio: fix null pointer exception when there is no oftree

[Lucas Stach]

Am Mittwoch, den 05.07.2017, 20:33 +0200 schrieb Sam Ravnborg:
> From d10f426e1b8cec7de257dabf59e7fe53a591b3c1 Mon Sep 17 00:00:00 2001
> From: Sam Ravnborg <srn at skov.dk>
> Date: Mon, 3 Jul 2017 22:07:41 +0200
> Subject: [PATCH 2/3] gpio: fix null pointer exception when there is no oftree
> 
> In a system with oftree support enabled but with no oftree the
> of_gpiochip_scan_hogs() would fail due to device_node equals NULL.
> 
> Check device_node and return with 0 in this situation, as this
> mirrors what would have happened before we added support for gpio-hogs.
> 
> Use IS_ENABLED(CONFIG_OFDEVICE) to teach compiler to leave
> out the of_* specific functions if not needed.
> 
> Fixes: 37e6bee7 ("gpiolib: Add support for GPIO "hog" nodes")
> Signed-off-by: Alexander Kurz <akurz at blala.de>
> Signed-off-by: Sam Ravnborg <sam at ravnborg.org>
> ---
>  drivers/gpio/gpiolib.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index a3e17ada0..2bd8ef2a8 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -379,6 +379,9 @@ static int of_gpiochip_scan_hogs(struct gpio_chip *chip)
>  	struct device_node *np;
>  	int ret, i;
>  
> +	if (!chip->dev->device_node)
> +		return 0;
> +
>  	for_each_available_child_of_node(chip->dev->device_node, np) {
>  		if (!of_property_read_bool(np, "gpio-hog"))
>  			continue;
> @@ -416,7 +419,10 @@ int gpiochip_add(struct gpio_chip *chip)
>  	for (i = chip->base; i < chip->base + chip->ngpio; i++)
>  		gpio_desc[i].chip = chip;
>  
> -	return of_gpiochip_scan_hogs(chip);
> +	if (IS_ENABLED(CONFIG_OFDEVICE))
> +		return of_gpiochip_scan_hogs(chip);
> +	else
> +		return 0;
>  }
>  
>  void gpiochip_remove(struct gpio_chip *chip)

I think this can be simplified to:

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index a3e17ada0d39..1a373ef149a5 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -379,6 +379,9 @@ static int of_gpiochip_scan_hogs(struct gpio_chip
*chip)
        struct device_node *np;
        int ret, i;

+       if (!IS_ENABLED(CONFIG_OFDEVICE) || !chip->dev->device_node)
+               return 0;
+
        for_each_available_child_of_node(chip->dev->device_node, np) {
                if (!of_property_read_bool(np, "gpio-hog"))
                        continue;

The optimizer should be able to work this out. Can you check that this
works for you? No need to resend, if it works I'll just commit this.

Regards,
Lucas