gpio: add flags to export GPIOs when requesting

Introduce new flags to automatically export GPIOs when using the convenience
functions gpio_request_one() or gpio_request_array(). This eases support for
custom boards where lots of GPIOs need to be exported for customer
applications.
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

Documentation/gpio.txt

@@ -322,6 +322,9 @@ where 'flags' is currently defined to specify the following properties:
 	* GPIOF_OPEN_DRAIN	- gpio pin is open drain type.
 	* GPIOF_OPEN_SOURCE	- gpio pin is open source type.
 
+	* GPIOF_EXPORT_DIR_FIXED	- export gpio to sysfs, keep direction
+	* GPIOF_EXPORT_DIR_CHANGEABLE	- also export, allow changing direction
+
 since GPIOF_INIT_* are only valid when configured as output, so group valid
 combinations as:
 

drivers/gpio/gpiolib.c

@@ -1302,8 +1302,18 @@ int gpio_request_one(unsigned gpio, unsigned long flags, const char *label)
 				(flags & GPIOF_INIT_HIGH) ? 1 : 0);
 
 	if (err)
-		gpio_free(gpio);
+		goto free_gpio;
+
+	if (flags & GPIOF_EXPORT) {
+		err = gpio_export(gpio, flags & GPIOF_EXPORT_CHANGEABLE);
+		if (err)
+			goto free_gpio;
+	}
+
+	return 0;
 
+ free_gpio:
+	gpio_free(gpio);
 	return err;
 }
 EXPORT_SYMBOL_GPL(gpio_request_one);

include/linux/gpio.h

@@ -20,6 +20,11 @@
 /* Gpio pin is open source */
 #define GPIOF_OPEN_SOURCE	(1 << 3)
 
+#define GPIOF_EXPORT		(1 << 2)
+#define GPIOF_EXPORT_CHANGEABLE	(1 << 3)
+#define GPIOF_EXPORT_DIR_FIXED	(GPIOF_EXPORT)
+#define GPIOF_EXPORT_DIR_CHANGEABLE (GPIOF_EXPORT | GPIOF_EXPORT_CHANGEABLE)
+
 /**
  * struct gpio - a structure describing a GPIO with configuration
  * @gpio:	the GPIO number