greybus: gpio: refuse to set value of input pins

Add warning and refuse to set output value for pin configured as input,
as the result of such an operation is undefined.

Remove incorrect todo-comment suggesting that the driver could
implicitly switch direction as part of the call.
Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/staging/greybus/gpio.c

@@ -273,14 +273,18 @@ static void gb_gpio_set_value_operation(struct gb_gpio_controller *ggc,
 	struct gb_gpio_set_value_request request;
 	int ret;
 
+	if (ggc->lines[which].direction == 1) {
+		dev_warn(ggc->chip.dev,
+			 "refusing to set value of input gpio %u\n", which);
+		return;
+	}
+
 	request.which = which;
 	request.value = value_high ? 1 : 0;
 	ret = gb_operation_sync(ggc->connection, GB_GPIO_TYPE_SET_VALUE,
 				&request, sizeof(request), NULL, 0);
-	if (!ret) {
-		/* XXX should this set direction to out? */
+	if (!ret)
 		ggc->lines[which].value = request.value;
-	}
 }
 
 static int gb_gpio_set_debounce_operation(struct gb_gpio_controller *ggc,