Add some notes to set_rumble's docs

src/sdl2/controller.rs

@@ -405,6 +405,15 @@ impl GameController {
 
     /// Set the rumble motors to their specified intensities, if supported.
     /// Automatically resets back to zero after `duration_ms` milliseconds have passed.
+    ///
+    /// # Notes
+    ///
+    /// The value range for the intensities is 0 to 0xFFFF.
+    ///
+    /// Do *not* use `std::u32::MAX` or similar for `duration_ms` if you want
+    /// the rumble effect to keep playing for a long time, as this results in
+    /// the effect ending immediately after starting due to an overflow.
+    /// Use some smaller, "huge enough" number instead.
     pub fn set_rumble(&mut self,
                       low_frequency_rumble: u16,
                       high_frequency_rumble: u16,

src/sdl2/joystick.rs

@@ -347,6 +347,15 @@ impl Joystick {
 
     /// Set the rumble motors to their specified intensities, if supported.
     /// Automatically resets back to zero after `duration_ms` milliseconds have passed.
+    ///
+    /// # Notes
+    ///
+    /// The value range for the intensities is 0 to 0xFFFF.
+    ///
+    /// Do *not* use `std::u32::MAX` or similar for `duration_ms` if you want
+    /// the rumble effect to keep playing for a long time, as this results in
+    /// the effect ending immediately after starting due to an overflow.
+    /// Use some smaller, "huge enough" number instead.
     pub fn set_rumble(&mut self,
                       low_frequency_rumble: u16,
                       high_frequency_rumble: u16,