[libmanette] device: Document rumble functions has_rumble() and rumble()

[Adrien Plazas <aplazas src gnome org>]

commit ac2dbd2beca67df3ff02c1b984ad1bfc086eed9b
Author: vanadiae <vanadiae35 gmail com>
Date:   Wed Oct 14 19:36:52 2020 +0200

    device: Document rumble functions has_rumble() and rumble()
    
    This is particularly needed as they are public API and rumbling
    can be hard to understand if you didn't use rumbles before.

 src/manette-device.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
---
diff --git a/src/manette-device.c b/src/manette-device.c
index bbd4f9f..b539475 100644
--- a/src/manette-device.c
+++ b/src/manette-device.c
@@ -818,6 +818,14 @@ manette_device_remove_user_mapping (ManetteDevice *self)
   g_object_unref (mapping_manager);
 }
 
+/**
+ * manette_device_has_rumble:
+ * @self: a #ManetteDevice
+ *
+ * Checks whether device @self has a rumble motor.
+ *
+ * Returns: whether device @self has a rumble motor.
+ */
 gboolean
 manette_device_has_rumble (ManetteDevice *self)
 {
@@ -834,6 +842,18 @@ manette_device_has_rumble (ManetteDevice *self)
   return TRUE;
 }
 
+/**
+ * manette_device_rumble:
+ * @self: a #ManetteDevice
+ * @strong_magnitude: the magnitude for the heavy rumbling motor, when there's one
+ * @weak_magnitude: the magnitude for the small rumbling motor
+ * @duration: the rumble effect play time in milliseconds, with a maximum of 32767.
+ *
+ * Make @self rumble during @duration milliseconds, with heavy motor rumbling at
+ * magnitude @strong_magnitude and the small rumbling motor at magnitude @weak_magnitude.
+ *
+ * Returns: whether the rumble effect was played.
+ */
 gboolean
 manette_device_rumble (ManetteDevice *self,
                        guint16        strong_magnitude,