gpiolib: Introduce gpiod_set_config()

The GPIO Aggregator will need a method to forward a .set_config() call
to its parent gpiochip.  This requires obtaining the gpio_chip and
offset for a given gpio_desc.  While gpiod_to_chip() is public,
gpio_chip_hwgpio() is not, so there is currently no method to obtain the
needed GPIO offset parameter.

Hence introduce a public gpiod_set_config() helper, which invokes the
.set_config() callback through a gpio_desc pointer, like is done for
most other gpio_chip callbacks.

Rewrite the existing gpiod_set_debounce() helper as a wrapper around
gpiod_set_config(), to avoid duplication.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200324135653.6676-5-geert+renesas@glider.beSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib.c

@@ -3431,6 +3431,26 @@ int gpiod_direction_output(struct gpio_desc *desc, int value)
 }
 EXPORT_SYMBOL_GPL(gpiod_direction_output);
 
+/**
+ * gpiod_set_config - sets @config for a GPIO
+ * @desc: descriptor of the GPIO for which to set the configuration
+ * @config: Same packed config format as generic pinconf
+ *
+ * Returns:
+ * 0 on success, %-ENOTSUPP if the controller doesn't support setting the
+ * configuration.
+ */
+int gpiod_set_config(struct gpio_desc *desc, unsigned long config)
+{
+	struct gpio_chip *chip;
+
+	VALIDATE_DESC(desc);
+	chip = desc->gdev->chip;
+
+	return gpio_do_set_config(chip, gpio_chip_hwgpio(desc), config);
+}
+EXPORT_SYMBOL_GPL(gpiod_set_config);
+
 /**
  * gpiod_set_debounce - sets @debounce time for a GPIO
  * @desc: descriptor of the GPIO for which to set debounce time
@@ -3442,14 +3462,10 @@ EXPORT_SYMBOL_GPL(gpiod_direction_output);
  */
 int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)
 {
-	struct gpio_chip	*chip;
-	unsigned long		config;
-
-	VALIDATE_DESC(desc);
-	chip = desc->gdev->chip;
+	unsigned long config;
 
 	config = pinconf_to_config_packed(PIN_CONFIG_INPUT_DEBOUNCE, debounce);
-	return gpio_do_set_config(chip, gpio_chip_hwgpio(desc), config);
+	return gpiod_set_config(desc, config);
 }
 EXPORT_SYMBOL_GPL(gpiod_set_debounce);
 

include/linux/gpio/consumer.h

@@ -157,6 +157,7 @@ int gpiod_set_raw_array_value_cansleep(unsigned int array_size,
 				       struct gpio_array *array_info,
 				       unsigned long *value_bitmap);
 
+int gpiod_set_config(struct gpio_desc *desc, unsigned long config);
 int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce);
 int gpiod_set_transitory(struct gpio_desc *desc, bool transitory);
 void gpiod_toggle_active_low(struct gpio_desc *desc);
@@ -473,6 +474,13 @@ static inline int gpiod_set_raw_array_value_cansleep(unsigned int array_size,
 	return 0;
 }
 
+static inline int gpiod_set_config(struct gpio_desc *desc, unsigned long config)
+{
+	/* GPIO can never have been requested */
+	WARN_ON(desc);
+	return -ENOSYS;
+}
+
 static inline int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)
 {
 	/* GPIO can never have been requested */