Re: [PATCH v3 2/2] gpiolib: check the 'ngpios' property in core gpiolib code

[Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>]

On Wed, Nov 24, 2021 at 01:28:50PM +0100, Bartosz Golaszewski wrote:
> Several drivers read the 'ngpios' device property on their own, but
> since it's defined as a standard GPIO property in the device tree bindings
> anyway, it's a good candidate for generalization. If the driver didn't
> set its gc->ngpio, try to read the 'ngpios' property from the GPIO
> device's firmware node before bailing out.

> Signed-off-by: Bartosz Golaszewski <brgl@xxxxxxxx>
> Suggested-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> ---
> v1 -> v2:
> - use device_property_read_u32() instead of fwnode_property_read_u32()
> - reverse the error check logic
> 
> v2 -> v3:
> - don't shadow errors other than -ENODATA in device_property_read_u32()
> 
>  drivers/gpio/gpiolib.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index ede8b8a7aa18..f79fd2551cf7 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -599,6 +599,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>  	int base = gc->base;
>  	unsigned int i;
>  	int ret = 0;
> +	u32 ngpios;
>  
>  	/*
>  	 * First: allocate and populate the internal stat container, and
> @@ -647,9 +648,17 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>  	}

>  	if (gc->ngpio == 0) {
> -		chip_err(gc, "tried to insert a GPIO chip with zero lines\n");
> -		ret = -EINVAL;
> -		goto err_free_descs;
> +		ret = device_property_read_u32(&gdev->dev, "ngpios", &ngpios);
> +		if (ret) {
> +			if (ret == -ENODATA) {
> +				chip_err(gc, "tried to insert a GPIO chip with zero lines\n");
> +				ret = -EINVAL;
> +			}
> +
> +			goto err_free_descs;
> +		}

And if the property returns 0 in ngpios?

What about the modified suggestion from previous version:

	if (gc->ngpio == 0) {
		ret = device_property_read_u32(&gdev->dev, "ngpios", &ngpios);
		/*
		 * -ENODATA means that there is no property found and
		 * we want to issue the error message to the user. Besides
		 * that, we want to return different error code to state
		 * that supplied value is not valid.
		 */
		if (ret == -ENODATA)
			ngpios = 0;
		else if (ret)
			return ret;

		gc->ngpio = ngpios;
	}

	if (gc->ngpio == 0) {
		chip_err(gc, "tried to insert a GPIO chip with zero lines\n");
		ret = -EINVAL;
		goto err_free_descs;
	}

?

> +		gc->ngpio = ngpios;
>  	}
>  
>  	if (gc->ngpio > FASTPATH_NGPIO)
> -- 
> 2.25.1
> 

-- 
With Best Regards,
Andy Shevchenko