dm: gpio: Add a driver GPIO translation method

Only the GPIO driver knows about the full GPIO device tree binding used by
a device. Add a method to allow the driver to provide this information to the
uclass, including the GPIO offset within the device and flags such as the
polarity.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/gpio/gpio-uclass.c

@@ -7,6 +7,7 @@
 #include <common.h>
 #include <dm.h>
 #include <errno.h>
+#include <fdtdec.h>
 #include <malloc.h>
 #include <asm/gpio.h>
 #include <linux/ctype.h>
@@ -91,6 +92,21 @@ int gpio_lookup_name(const char *name, struct udevice **devp,
 	return 0;
 }
 
+int gpio_find_and_xlate(struct gpio_desc *desc,
+			struct fdtdec_phandle_args *args)
+{
+	struct dm_gpio_ops *ops = gpio_get_ops(desc->dev);
+
+	/* Use the first argument as the offset by default */
+	if (args->args_count > 0)
+		desc->offset = args->args[0];
+	else
+		desc->offset = -1;
+	desc->flags = 0;
+
+	return ops->xlate ? ops->xlate(desc->dev, desc, args) : 0;
+}
+
 static int dm_gpio_request(struct gpio_desc *desc, const char *label)
 {
 	struct udevice *dev = desc->dev;

include/asm-generic/gpio.h

@@ -171,6 +171,8 @@ int gpio_get_raw_function(struct udevice *dev, int offset, const char **namep);
 int gpio_requestf(unsigned gpio, const char *fmt, ...)
 		__attribute__ ((format (__printf__, 2, 3)));
 
+struct fdtdec_phandle_args;
+
 /**
  * struct struct dm_gpio_ops - Driver model GPIO operations
  *
@@ -214,6 +216,33 @@ struct dm_gpio_ops {
 	 * @return current function - GPIOF_...
 	 */
 	int (*get_function)(struct udevice *dev, unsigned offset);
+
+	/**
+	 * xlate() - Translate phandle arguments into a GPIO description
+	 *
+	 * This function should set up the fields in desc according to the
+	 * information in the arguments. The uclass will have set up:
+	 *
+	 *   @desc->dev to @dev
+	 *   @desc->flags to 0
+	 *   @desc->offset to the value of the first argument in args, if any,
+	 *		otherwise -1 (which is invalid)
+	 *
+	 * This method is optional so if the above defaults suit it can be
+	 * omitted. Typical behaviour is to set up the GPIOD_ACTIVE_LOW flag
+	 * in desc->flags.
+	 *
+	 * Note that @dev is passed in as a parameter to follow driver model
+	 * uclass conventions, even though it is already available as
+	 * desc->dev.
+	 *
+	 * @dev:	GPIO device
+	 * @desc:	Place to put GPIO description
+	 * @args:	Arguments provided in descripion
+	 * @return 0 if OK, -ve on error
+	 */
+	int (*xlate)(struct udevice *dev, struct gpio_desc *desc,
+		     struct fdtdec_phandle_args *args);
 };
 
 /**