gpiolib: add support for biasing output lines

Allow pull up/down bias to be set on output lines.
Use case is for open source or open drain applications where
internal pull up/down may conflict with external biasing.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

drivers/gpio/gpiolib.c

@@ -556,8 +556,9 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
 	     (lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE)))
 		return -EINVAL;
 
-	/* Bias flags only allowed for input mode. */
+	/* Bias flags only allowed for input or output mode. */
-	if (!(lflags & GPIOHANDLE_REQUEST_INPUT) &&
+	if (!((lflags & GPIOHANDLE_REQUEST_INPUT) ||
+	      (lflags & GPIOHANDLE_REQUEST_OUTPUT)) &&
 	    ((lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE) ||
 	     (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP) ||
 	     (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN)))
@@ -3169,6 +3170,9 @@ int gpiod_direction_output(struct gpio_desc *desc, int value)
 	}
 
 set_output_value:
+	ret = gpio_set_bias(gc, desc);
+	if (ret)
+		return ret;
 	return gpiod_direction_output_raw_commit(desc, value);
 
 set_output_flag: