update README to reflect callbacks

1 files changed, 24 insertions, 1 deletions

diff --git a/README.md b/README.md
index de38d9e..3424af7 100644
--- a/README.md
+++ b/README.md
@@ -107,8 +107,31 @@ Resume a channel.
 This function has no effect if the channel is already playing.
 
 
+### `void mossrose_channel_set_callback(int channel, mossrose_channel_callback_t callback, void *userdata)` ###
+
+Set a callback to run each time playback of audio on a channel completes.
+
+  * `channel` - the channel to attach to
+  * `callback` - pointer to the callback function.
+  * `userdata` - pointer to data to pass to the callback function.
+
+The callback function should return `void` and have signature `(int channel, 
+void *userdata)`, where
+
+  * `channel` is the index of the channel triggering the callback
+  * `userdata` is the user data bound to the callback via the `userdata` 
+     argument to the setter function.
+
+Callbacks will not be triggered on their own! You must periodically call
+`mossrose_poll_callbacks` to trigger them.
+
+
+### `void mossrose_poll_callbacks()` ###
+
+Check all channels for playback-finished callbacks and run them if necessary.
+
+
 todo
 ----
 
-  * playback finished callback
   * audio loading