pinctrl: introduce pinctrl_gpio_get_config()

This is a counterpart of pinctrl_gpio_set_config(), which will be used
to implement the ->get() interface in a GPIO driver for SCMI.

This also requires that we create a stub so pin_config_get_for_pin()
can build when CONFIG_PINCONF is disabled.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>

Author: AKASHI Takahiro

drivers/pinctrl/core.c

@@ -30,6 +30,7 @@
 #include <linux/pinctrl/consumer.h>
 #include <linux/pinctrl/devinfo.h>
 #include <linux/pinctrl/machine.h>
+#include <linux/pinctrl/pinconf.h>
 #include <linux/pinctrl/pinctrl.h>
 
 #include "core.h"
@@ -938,6 +939,36 @@ int pinctrl_gpio_set_config(struct gpio_chip *gc, unsigned int offset,
 }
 EXPORT_SYMBOL_GPL(pinctrl_gpio_set_config);
 
+/**
+ * pinctrl_gpio_get_config() - Get the config for a given GPIO pin
+ * @gc: GPIO chip structure from the GPIO subsystem
+ * @offset: hardware offset of the GPIO relative to the controller
+ * @config: the configuration to query.  On success it holds the result
+ * Return: 0 on success, negative errno otherwise
+ */
+int pinctrl_gpio_get_config(struct gpio_chip *gc, unsigned int offset, unsigned long *config)
+{
+	struct pinctrl_gpio_range *range;
+	struct pinctrl_dev *pctldev;
+	int ret, pin;
+
+	ret = pinctrl_get_device_gpio_range(gc, offset, &pctldev, &range);
+	if (ret)
+		return ret;
+
+	mutex_lock(&pctldev->mutex);
+	pin = gpio_to_pin(range, gc, offset);
+	ret = pin_config_get_for_pin(pctldev, pin, config);
+	mutex_unlock(&pctldev->mutex);
+
+	if (ret)
+		return ret;
+
+	*config = pinconf_to_config_argument(*config);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pinctrl_gpio_get_config);
+
 static struct pinctrl_state *find_state(struct pinctrl *p,
 					const char *name)
 {

drivers/pinctrl/pinconf.h

@@ -74,6 +74,12 @@ static inline int pinconf_set_config(struct pinctrl_dev *pctldev, unsigned int p
 	return -ENOTSUPP;
 }
 
+static inline int pin_config_get_for_pin(struct pinctrl_dev *pctldev, unsigned int pin,
+			   unsigned long *config)
+{
+	return -ENOTSUPP;
+}
+
 #endif
 
 #if defined(CONFIG_PINCONF) && defined(CONFIG_DEBUG_FS)

include/linux/pinctrl/consumer.h

@@ -35,6 +35,8 @@ int pinctrl_gpio_direction_output(struct gpio_chip *gc,
 				  unsigned int offset);
 int pinctrl_gpio_set_config(struct gpio_chip *gc, unsigned int offset,
 				unsigned long config);
+int pinctrl_gpio_get_config(struct gpio_chip *gc, unsigned int offset,
+			    unsigned long *config);
 
 struct pinctrl * __must_check pinctrl_get(struct device *dev);
 void pinctrl_put(struct pinctrl *p);
@@ -101,6 +103,13 @@ pinctrl_gpio_direction_output(struct gpio_chip *gc, unsigned int offset)
 	return 0;
 }
 
+static inline int
+pinctrl_gpio_get_config(struct gpio_chip *gc, unsigned int offset,
+			unsigned long *config)
+{
+	return 0;
+}
+
 static inline int
 pinctrl_gpio_set_config(struct gpio_chip *gc, unsigned int offset,
 			    unsigned long config)