gpio: Replace direction_input() and direction_output()

The new update_flags() method is more flexible since it allows the
driver to see the full flags all at once. Use that in preference to these
two functions. Add comments to that effect.

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

Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index 7d1e19a..f0c835e 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -260,10 +260,32 @@
 struct dm_gpio_ops {
 	int (*request)(struct udevice *dev, unsigned offset, const char *label);
 	int (*rfree)(struct udevice *dev, unsigned int offset);
+
+	/**
+	 * direction_input() - deprecated
+	 *
+	 * Equivalent to set_flags(...GPIOD_IS_IN)
+	 */
 	int (*direction_input)(struct udevice *dev, unsigned offset);
+
+	/**
+	 * direction_output() - deprecated
+	 *
+	 * Equivalent to set_flags(...GPIOD_IS_OUT) with GPIOD_IS_OUT_ACTIVE
+	 * also set if @value
+	 */
 	int (*direction_output)(struct udevice *dev, unsigned offset,
 				int value);
+
 	int (*get_value)(struct udevice *dev, unsigned offset);
+
+	/**
+	 * set_value() - Sets the GPIO value of an output
+	 *
+	 * If the driver provides an @set_flags() method then that is used
+	 * in preference to this, with GPIOD_IS_OUT_ACTIVE set according to
+	 * @value.
+	 */
 	int (*set_value)(struct udevice *dev, unsigned offset, int value);
 	/**
 	 * get_function() Get the GPIO function
@@ -320,7 +342,9 @@
 	 * uclass, so the driver always sees the value that should be set at the
 	 * pin (1=high, 0=low).
 	 *
-	 * This method is optional.
+	 * This method is required and should be implemented by new drivers. At
+	 * some point, it will supersede direction_input() and
+	 * direction_output(), which wil be removed.
 	 *
 	 * @dev:	GPIO device
 	 * @offset:	GPIO offset within that device