Re: [PATCH v4 02/13] gpiolib: have a single place of calling set_config()

[Guenter Roeck <linux@roeck-us.net>]

On Tue, Dec 24, 2019 at 01:06:58PM +0100, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> 
> Instead of calling the gpiochip's set_config() callback directly and
> checking its existence every time - just add a new routine that performs
> this check internally. Call it in gpio_set_config() and
> gpiod_set_transitory(). Also call it in gpiod_set_debounce() and drop
> the check for chip->set() as it's irrelevant to this config option.
> 
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

This patch made it into mainline, even though a regression was reported
against it by Geert. Please note that it is not just a theoretic problem
but _does_ indeed cause regressions.

Guenter

> ---
>  drivers/gpio/gpiolib.c | 21 ++++++++++++---------
>  1 file changed, 12 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index e5d101ee9ada..616e431039fc 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -3042,6 +3042,15 @@ EXPORT_SYMBOL_GPL(gpiochip_free_own_desc);
>   * rely on gpio_request() having been called beforehand.
>   */
>  
> +static int gpio_do_set_config(struct gpio_chip *gc, unsigned int offset,
> +			      enum pin_config_param mode)
> +{
> +	if (!gc->set_config)
> +		return -ENOTSUPP;
> +
> +	return gc->set_config(gc, offset, mode);
> +}
> +
>  static int gpio_set_config(struct gpio_chip *gc, unsigned int offset,
>  			   enum pin_config_param mode)
>  {
> @@ -3060,7 +3069,7 @@ static int gpio_set_config(struct gpio_chip *gc, unsigned int offset,
>  	}
>  
>  	config = PIN_CONF_PACKED(mode, arg);
> -	return gc->set_config ? gc->set_config(gc, offset, config) : -ENOTSUPP;
> +	return gpio_do_set_config(gc, offset, mode);
>  }
>  
>  static int gpio_set_bias(struct gpio_chip *chip, struct gpio_desc *desc)
> @@ -3294,15 +3303,9 @@ int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)
>  
>  	VALIDATE_DESC(desc);
>  	chip = desc->gdev->chip;
> -	if (!chip->set || !chip->set_config) {
> -		gpiod_dbg(desc,
> -			  "%s: missing set() or set_config() operations\n",
> -			  __func__);
> -		return -ENOTSUPP;
> -	}
>  
>  	config = pinconf_to_config_packed(PIN_CONFIG_INPUT_DEBOUNCE, debounce);
> -	return chip->set_config(chip, gpio_chip_hwgpio(desc), config);
> +	return gpio_do_set_config(chip, gpio_chip_hwgpio(desc), config);
>  }
>  EXPORT_SYMBOL_GPL(gpiod_set_debounce);
>  
> @@ -3339,7 +3342,7 @@ int gpiod_set_transitory(struct gpio_desc *desc, bool transitory)
>  	packed = pinconf_to_config_packed(PIN_CONFIG_PERSIST_STATE,
>  					  !transitory);
>  	gpio = gpio_chip_hwgpio(desc);
> -	rc = chip->set_config(chip, gpio, packed);
> +	rc = gpio_do_set_config(chip, gpio, packed);
>  	if (rc == -ENOTSUPP) {
>  		dev_dbg(&desc->gdev->dev, "Persistence not supported for GPIO %d\n",
>  				gpio);