events: Rework event subsystem (add_event, send_event) to be more versatile.

add_event_ex is added that takes an extra user_data pointer. This pointer is
passed to the callback (add_event and add_event_ex have slightly different
callbacks types). All callbacks also get the event id passed. Events added
with add_event_ex must be removed with remove_event_ex because the user_data
pointer must match in addition to the callback pointer.

On the other add_event is simplified to omit the oneshort parameter which
was almost always false (still there with add_event_ex).

As a side effect the ata_idle_notify callbacks are changed as well, they
do not take a data parameter anymore which was always NULL anyway.

This commit also adds some documentation to events.h

Change-Id: I13e29a0f88ef908f175b376d83550f9e0231f772

25 files changed, 247 insertions, 149 deletions

diff --git a/apps/gui/list.c b/apps/gui/list.c
index c393340c57..8663abe8a0 100644
--- a/apps/gui/list.c
+++ b/apps/gui/list.c
@@ -66,16 +66,17 @@ static bool list_is_dirty(struct gui_synclist *list)
     return TIME_BEFORE(list->dirty_tick, last_dirty_tick);
 }
 
-static void list_force_reinit(void *param)
+static void list_force_reinit(unsigned short id, void *param, void *last_dirty_tick)
 {
+    (void)id;
     (void)param;
-    last_dirty_tick = current_tick;
+    *(int *)last_dirty_tick = current_tick;
 }
 
 void list_init(void)
 {
     last_dirty_tick = current_tick;
-    add_event(GUI_EVENT_THEME_CHANGED, false, list_force_reinit);
+    add_event_ex(GUI_EVENT_THEME_CHANGED, false, list_force_reinit, &last_dirty_tick);
 }
 
 static void list_init_viewports(struct gui_synclist *list)
@@ -611,8 +612,9 @@ bool gui_synclist_keyclick_callback(int action, void* data)
  */
 static struct gui_synclist *current_lists;
 static bool ui_update_event_registered = false;
-static void _lists_uiviewport_update_callback(void *data)
+static void _lists_uiviewport_update_callback(unsigned short id, void *data)
 {
+    (void)id;
     (void)data;
     if (current_lists)
         gui_synclist_draw(current_lists);
@@ -801,8 +803,7 @@ int list_do_action_timeout(struct gui_synclist *lists, int timeout)
     {
         if (!ui_update_event_registered)
             ui_update_event_registered = 
-                    add_event(GUI_EVENT_NEED_UI_UPDATE, false,
-                            _lists_uiviewport_update_callback);
+                    add_event(GUI_EVENT_NEED_UI_UPDATE, _lists_uiviewport_update_callback);
         current_lists = lists;
     }
     if(lists->scheduled_talk_tick)
diff --git a/apps/gui/statusbar-skinned.c b/apps/gui/statusbar-skinned.c
index c991d8ea40..c4cc37d539 100644
--- a/apps/gui/statusbar-skinned.c
+++ b/apps/gui/statusbar-skinned.c
@@ -178,8 +178,9 @@ void sb_skin_update(enum screen_type screen, bool force)
     }
 }
 
-void do_sbs_update_callback(void *param)
+void do_sbs_update_callback(unsigned short id, void *param)
 {
+    (void)id;
     (void)param;
     /* the WPS handles changing the actual id3 data in the id3 pointers
      * we imported, we just want a full update */
diff --git a/apps/gui/statusbar-skinned.h b/apps/gui/statusbar-skinned.h
index ac12dfa1aa..237ec45c82 100644
--- a/apps/gui/statusbar-skinned.h
+++ b/apps/gui/statusbar-skinned.h
@@ -66,5 +66,5 @@ int sb_postproccess(enum screen_type screen, struct wps_data *data);
 #define sb_preproccess NULL
 #define sb_postproccess NULL
 #endif
-void do_sbs_update_callback(void *param);
+void do_sbs_update_callback(unsigned short id, void *param);
 #endif /* __STATUSBAR_SKINNED_H__ */
diff --git a/apps/gui/viewport.c b/apps/gui/viewport.c
index aeb884a95d..194954c1d2 100644
--- a/apps/gui/viewport.c
+++ b/apps/gui/viewport.c
@@ -69,7 +69,7 @@ struct viewport_stack_item
 };
 
 #ifdef HAVE_LCD_BITMAP
-static void viewportmanager_redraw(void* data);
+static void viewportmanager_redraw(unsigned short id, void* data);
 
 static int theme_stack_top[NB_SCREENS]; /* the last item added */
 static struct viewport_stack_item theme_stack[NB_SCREENS][VPSTACK_DEPTH];
@@ -80,14 +80,12 @@ static void toggle_events(bool enable)
 {
     if (enable)
     {
-        add_event(GUI_EVENT_ACTIONUPDATE, false, viewportmanager_redraw);
+        add_event(GUI_EVENT_ACTIONUPDATE, viewportmanager_redraw);
 #if defined(HAVE_LCD_ENABLE) || defined(HAVE_LCD_SLEEP)
-        add_event(LCD_EVENT_ACTIVATION, false, do_sbs_update_callback);
+        add_event(LCD_EVENT_ACTIVATION, do_sbs_update_callback);
 #endif
-        add_event(PLAYBACK_EVENT_TRACK_CHANGE, false,
-                                                do_sbs_update_callback);
-        add_event(PLAYBACK_EVENT_NEXTTRACKID3_AVAILABLE, false,
-                                                do_sbs_update_callback);
+        add_event(PLAYBACK_EVENT_TRACK_CHANGE, do_sbs_update_callback);
+        add_event(PLAYBACK_EVENT_NEXTTRACKID3_AVAILABLE, do_sbs_update_callback);
     }
     else
     {
@@ -232,8 +230,9 @@ int viewport_get_nb_lines(const struct viewport *vp)
 #endif
 }
 
-static void viewportmanager_redraw(void* data)
+static void viewportmanager_redraw(unsigned short id, void* data)
 {
+    (void)id;
     FOR_NB_SCREENS(i)
     {
 #ifdef HAVE_LCD_BITMAP
@@ -256,7 +255,7 @@ void viewportmanager_init()
         viewportmanager_theme_enable(i, true, NULL);
     }
 #else
-    add_event(GUI_EVENT_ACTIONUPDATE, false, viewportmanager_redraw);
+    add_event(GUI_EVENT_ACTIONUPDATE, viewportmanager_redraw);
 #endif
 }
 
diff --git a/apps/gui/wps.c b/apps/gui/wps.c
index b4c3f40e9f..d1161ea71d 100644
--- a/apps/gui/wps.c
+++ b/apps/gui/wps.c
@@ -74,8 +74,7 @@
 
 /* initial setup of wps_data  */
 static void wps_state_init(void);
-static void track_changed_callback(void *param);
-static void nextid3available_callback(void* param);
+static void track_info_callback(unsigned short id, void *param);
 
 #define WPS_DEFAULTCFG WPS_DIR "/rockbox_default.wps"
 #ifdef HAVE_REMOTE_LCD
@@ -626,8 +625,9 @@ static void play_hop(int direction)
  * we suppress updates until the wps is activated again (the lcd driver will
  * call this hook to issue an instant update)
  * */
-static void wps_lcd_activation_hook(void *param)
+static void wps_lcd_activation_hook(unsigned short id, void *param)
 {
+    (void)id;
     (void)param;
     skin_request_full_update(WPS);
     /* force timeout in wps main loop, so that the update is instantly */
@@ -1119,7 +1119,7 @@ long gui_wps_show(void)
             restore = false;
             restoretimer = RESTORE_WPS_INSTANTLY;
 #if defined(HAVE_LCD_ENABLE) || defined(HAVE_LCD_SLEEP)
-            add_event(LCD_EVENT_ACTIVATION, false, wps_lcd_activation_hook);
+            add_event(LCD_EVENT_ACTIVATION, wps_lcd_activation_hook);
 #endif
         /* we remove the update delay since it's not very usable in the wps,
          * e.g. during volume changing or ffwd/rewind */
@@ -1187,35 +1187,27 @@ long gui_wps_show(void)
 }
 
 /* this is called from the playback thread so NO DRAWING! */
-static void track_changed_callback(void *param)
+static void track_info_callback(unsigned short id, void *param)
 {
     struct wps_state *state = skin_get_global_state();
-    state->id3 = ((struct track_event *)param)->id3;
-    state->nid3 = audio_next_track();
-    if (state->id3->cuesheet)
+
+    if (id == PLAYBACK_EVENT_TRACK_CHANGE || id == PLAYBACK_EVENT_CUR_TRACK_READY)
     {
-        cue_find_current_track(state->id3->cuesheet, state->id3->elapsed);
+        state->id3 = ((struct track_event *)param)->id3;
+        if (state->id3->cuesheet)
+        {
+            cue_find_current_track(state->id3->cuesheet, state->id3->elapsed);
+        }
     }
-    skin_request_full_update(WPS);
-}
-static void nextid3available_callback(void* param)
-{
-    (void)param;
-    skin_get_global_state()->nid3 = audio_next_track();
-    skin_request_full_update(WPS);
-}
-
 #ifdef AUDIO_FAST_SKIP_PREVIEW
-/* this is called on the audio_skip caller thread */
-static void track_skip_callback(void *param)
-{
-    struct wps_state *state = skin_get_global_state();
-    state->id3 = audio_current_track();
-    state->nid3 = audio_next_track();
+    else if (id == PLAYBACK_EVENT_TRACK_SKIP)
+    {
+        state->id3 = audio_current_track();
+    }
+#endif
+    skin_get_global_state()->nid3 = audio_next_track();
     skin_request_full_update(WPS);
-    (void)param;
 }
-#endif /* AUDIO_FAST_SKIP_PREVIEW */
 
 static void wps_state_init(void)
 {
@@ -1235,15 +1227,15 @@ static void wps_state_init(void)
     /* We'll be updating due to restore initialized with true */
     skin_request_full_update(WPS);
     /* add the WPS track event callbacks */
-    add_event(PLAYBACK_EVENT_TRACK_CHANGE, false, track_changed_callback);
-    add_event(PLAYBACK_EVENT_NEXTTRACKID3_AVAILABLE, false, nextid3available_callback);
+    add_event(PLAYBACK_EVENT_TRACK_CHANGE, track_info_callback);
+    add_event(PLAYBACK_EVENT_NEXTTRACKID3_AVAILABLE, track_info_callback);
 #if CONFIG_CODEC == SWCODEC
     /* Use the same callback as ..._TRACK_CHANGE for when remaining handles have
        finished */
-    add_event(PLAYBACK_EVENT_CUR_TRACK_READY, false, track_changed_callback);
+    add_event(PLAYBACK_EVENT_CUR_TRACK_READY, track_info_callback);
 #endif
 #ifdef AUDIO_FAST_SKIP_PREVIEW
-    add_event(PLAYBACK_EVENT_TRACK_SKIP, false, track_skip_callback);
+    add_event(PLAYBACK_EVENT_TRACK_SKIP, track_info_callback);
 #endif
 }
 
diff --git a/apps/hosted/android/notification.c b/apps/hosted/android/notification.c
index 874cd3bcef..66715d26f9 100644
--- a/apps/hosted/android/notification.c
+++ b/apps/hosted/android/notification.c
@@ -44,8 +44,9 @@ static const struct dim dim = { .width = 200, .height = 200 };
 
 /*
  * notify about track change, and show track info */
-static void track_changed_callback(void *param)
+static void track_changed_callback(unsigned short id, void *param)
 {
+    (void)id;
     struct mp3entry* id3 = ((struct track_event *)param)->id3;
     JNIEnv e = *env_ptr;
     if (id3)
@@ -106,8 +107,9 @@ static void track_changed_callback(void *param)
 
 /*
  * notify about track finishing */
-static void track_finished_callback(void *param)
+static void track_finished_callback(unsigned short id, void *param)
 {
+    (void)id;
     if (((struct track_event *)param)->flags & TEF_REWIND)
         return; /* Not a true track end */
 
@@ -144,6 +146,6 @@ void notification_init(void)
     finishNotification = e->GetMethodID(env_ptr, class, "finishNotification",
                                         "()V");
 
-    add_event(PLAYBACK_EVENT_TRACK_CHANGE, false, track_changed_callback);
-    add_event(PLAYBACK_EVENT_TRACK_FINISH, false, track_finished_callback);
+    add_event(PLAYBACK_EVENT_TRACK_CHANGE track_changed_callback);
+    add_event(PLAYBACK_EVENT_TRACK_FINISH track_finished_callback);
 }
diff --git a/apps/iap/iap-core.c b/apps/iap/iap-core.c
index 7226a908c5..4fa9c09a47 100644
--- a/apps/iap/iap-core.c
+++ b/apps/iap/iap-core.c
@@ -349,8 +349,9 @@ static void iap_thread(void)
 }
 
 /* called by playback when the next track starts */
-static void iap_track_changed(void *ignored)
+static void iap_track_changed(unsigned short id, void *ignored)
 {
+    (void)id;
     (void)ignored;
     if ((interface_state == IST_EXTENDED) && device.do_notify) {
         long playlist_pos = playlist_next(0);
@@ -401,7 +402,7 @@ static void iap_start(void)
     if (!tid)
         panicf("Could not create iap thread");
     timeout_register(&iap_task_tmo, iap_task, MS_TO_TICKS(100), (intptr_t)NULL);
-    add_event(PLAYBACK_EVENT_TRACK_CHANGE, false, iap_track_changed);
+    add_event(PLAYBACK_EVENT_TRACK_CHANGE, iap_track_changed);
 
     /* Since we cannot allocate memory while in interrupt context
      * post a message to our own queue to get that done
diff --git a/apps/playback.c b/apps/playback.c
index 80a0585b17..eba90f9a0a 100644
--- a/apps/playback.c
+++ b/apps/playback.c
@@ -334,17 +334,18 @@ enum audio_start_playback_flags
 static void audio_start_playback(const struct audio_resume_info *resume_info,
                                  unsigned int flags);
 static void audio_stop_playback(void);
-static void buffer_event_buffer_low_callback(void *data);
-static void buffer_event_rebuffer_callback(void *data);
-static void buffer_event_finished_callback(void *data);
+static void buffer_event_buffer_low_callback(unsigned short id, void *data, void *user_data);
+static void buffer_event_rebuffer_callback(unsigned short id, void *data);
+static void buffer_event_finished_callback(unsigned short id, void *data);
 void audio_pcmbuf_sync_position(void);
 
 
 /**************************************/
 
 /** --- voice event --- **/
-void playback_voice_event(void *data)
+void playback_voice_event(unsigned short id, void *data)
 {
+    (void)id;
     /* Make audio play softly while voice is speaking */
     pcmbuf_soft_mode(*(bool *)data);
 }
@@ -1757,7 +1758,7 @@ static int audio_load_track(void)
                    should have been cleared already */
                 logf("%s(): finishing load: %d", __func__, info->id3_hid);
                 filling = STATE_FILLING;
-                buffer_event_finished_callback(&info->id3_hid);
+                buffer_event_finished_callback(BUFFER_EVENT_FINISHED, &info->id3_hid);
                 return LOAD_TRACK_OK;
             }
         }
@@ -2585,8 +2586,8 @@ static void audio_start_playback(const struct audio_resume_info *resume_info,
 
     /* Add these now - finish event for the first id3 will most likely be sent
        immediately */
-    add_event(BUFFER_EVENT_REBUFFER, false, buffer_event_rebuffer_callback);
-    add_event(BUFFER_EVENT_FINISHED, false, buffer_event_finished_callback);
+    add_event(BUFFER_EVENT_REBUFFER, buffer_event_rebuffer_callback);
+    add_event(BUFFER_EVENT_FINISHED, buffer_event_finished_callback);
 
     if (old_status == PLAY_STOPPED)
     {
@@ -2647,7 +2648,7 @@ static void audio_stop_playback(void)
     /* Close all tracks and mark them NULL */
     remove_event(BUFFER_EVENT_REBUFFER, buffer_event_rebuffer_callback);
     remove_event(BUFFER_EVENT_FINISHED, buffer_event_finished_callback);
-    remove_event(BUFFER_EVENT_BUFFER_LOW, buffer_event_buffer_low_callback);
+    remove_event_ex(BUFFER_EVENT_BUFFER_LOW, buffer_event_buffer_low_callback, NULL);
 
     track_list_clear(TRACK_LIST_CLEAR_ALL);
 
@@ -3164,8 +3165,8 @@ void audio_playback_handler(struct queue_event *ev)
                 /* End of buffering for now, let's calculate the watermark,
                    register for a low buffer event and unboost */
                 audio_update_filebuf_watermark(0);
-                add_event(BUFFER_EVENT_BUFFER_LOW, true,
-                          buffer_event_buffer_low_callback);
+                add_event_ex(BUFFER_EVENT_BUFFER_LOW, true,
+                        buffer_event_buffer_low_callback, NULL);
             }
             /* Fall-through */
         case STATE_FINISHED:
@@ -3200,27 +3201,31 @@ void audio_playback_handler(struct queue_event *ev)
 /* --- Buffering callbacks --- */
 
 /* Called when fullness is below the watermark level */
-static void buffer_event_buffer_low_callback(void *data)
+static void buffer_event_buffer_low_callback(unsigned short id, void *ev_data, void *user_data)
 {
     logf("low buffer callback");
     LOGFQUEUE("buffering > audio Q_AUDIO_BUFFERING: buffer low");
     audio_queue_post(Q_AUDIO_BUFFERING, BUFFER_EVENT_BUFFER_LOW);
-    (void)data;
+    (void)id;
+    (void)ev_data;
+    (void)user_data;
 }
 
 /* Called when handles must be discarded in order to buffer new data */
-static void buffer_event_rebuffer_callback(void *data)
+static void buffer_event_rebuffer_callback(unsigned short id, void *ev_data)
 {
     logf("rebuffer callback");
     LOGFQUEUE("buffering > audio Q_AUDIO_BUFFERING: rebuffer");
     audio_queue_post(Q_AUDIO_BUFFERING, BUFFER_EVENT_REBUFFER);
-    (void)data;
+    (void)id;
+    (void)ev_data;
 }
 
 /* A handle has completed buffering and all required data is available */
-static void buffer_event_finished_callback(void *data)
+static void buffer_event_finished_callback(unsigned short id, void *ev_data)
 {
-    int hid = *(const int *)data;
+    (void)id;
+    int hid = *(const int *)ev_data;
     const enum data_type htype = buf_handle_data_type(hid);
 
     logf("handle %d finished buffering (type:%u)", hid, (unsigned)htype);
@@ -3717,7 +3722,7 @@ void INIT_ATTR playback_init(void)
     track_list_init();
     buffering_init();
     pcmbuf_update_frequency();
-    add_event(PLAYBACK_EVENT_VOICE_PLAYING, false, playback_voice_event);
+    add_event(PLAYBACK_EVENT_VOICE_PLAYING, playback_voice_event);
 #ifdef HAVE_CROSSFADE
     /* Set crossfade setting for next buffer init which should be about... */
     pcmbuf_request_crossfade_enable(global_settings.crossfade);
diff --git a/apps/playlist.c b/apps/playlist.c
index 0e73781238..a066dd2ea0 100755
--- a/apps/playlist.c
+++ b/apps/playlist.c
@@ -1223,9 +1223,8 @@ static int compare(const void* p1, const void* p2)
  * without affecting playlist load up performance.  This thread also flushes
  * any pending control commands when the disk spins up.
  */
-static void playlist_flush_callback(void *param)
+static void playlist_flush_callback(void)
 {
-    (void)param;
     struct playlist_info *playlist;
     playlist = &current_playlist;
     if (playlist->control_fd >= 0)
diff --git a/apps/plugin.h b/apps/plugin.h
index ffdfa8fb77..874f6e0069 100644
--- a/apps/plugin.h
+++ b/apps/plugin.h
@@ -160,12 +160,12 @@ void* plugin_get_buffer(size_t *buffer_size);
 #define PLUGIN_MAGIC 0x526F634B /* RocK */
 
 /* increase this every time the api struct changes */
-#define PLUGIN_API_VERSION 227
+#define PLUGIN_API_VERSION 228
 
 /* update this to latest version if a change to the api struct breaks
    backwards compatibility (and please take the opportunity to sort in any
    new function which are "waiting" at the end of the function table) */
-#define PLUGIN_MIN_API_VERSION 227
+#define PLUGIN_MIN_API_VERSION 228
 
 /* plugin return codes */
 /* internal returns start at 0x100 to make exit(1..255) work */
@@ -450,8 +450,8 @@ struct plugin_api {
     void (*storage_spin)(void);
     void (*storage_spindown)(int seconds);
 #if USING_STORAGE_CALLBACK
-    void (*register_storage_idle_func)(void (*function)(void *data));
-    void (*unregister_storage_idle_func)(void (*function)(void *data), bool run);
+    void (*register_storage_idle_func)(void (*function)(void));
+    void (*unregister_storage_idle_func)(void (*function)(void), bool run);
 #endif /* USING_STORAGE_CALLBACK */
     void (*reload_directory)(void);
     char *(*create_numbered_filename)(char *buffer, const char *path,
@@ -569,8 +569,8 @@ struct plugin_api {
     void (*profile_func_exit)(void *this_fn, void *call_site);
 #endif
     /* event api */
-    bool (*add_event)(unsigned short id, bool oneshot, void (*handler)(void *data));
-    void (*remove_event)(unsigned short id, void (*handler)(void *data));
+    bool (*add_event)(unsigned short id, void (*handler)(unsigned short id, void *data));
+    void (*remove_event)(unsigned short id, void (*handler)(unsigned short id, void *data));
     void (*send_event)(unsigned short id, void *data);
 
 #if (CONFIG_PLATFORM & PLATFORM_HOSTED)
diff --git a/apps/plugins/battery_bench.c b/apps/plugins/battery_bench.c
index 93876d0807..174a589d8f 100644
--- a/apps/plugins/battery_bench.c
+++ b/apps/plugins/battery_bench.c
@@ -359,9 +359,8 @@ static unsigned int charge_state(void)
 #endif
 
 
-static void flush_buffer(void* data)
+static void flush_buffer(void)
 {
-    (void)data;
     int fd;
     unsigned int i;
 
@@ -445,7 +444,7 @@ static void thread(void)
            for this to occur because it requires > 16 hours of no disk activity.
          */
         if (buf_idx == BUF_ELEMENTS) {
-            flush_buffer(NULL);
+            flush_buffer();
         }
         
         /* sleep some time until next measurement */
@@ -479,7 +478,7 @@ static void thread(void)
     /* unregister flush callback and flush to disk */
     rb->unregister_storage_idle_func(flush_buffer, true);
 #else
-    flush_buffer(NULL);
+    flush_buffer();
 #endif
     
     /* log end of bench and exit reason */
diff --git a/apps/plugins/mpegplayer/mpeg_settings.c b/apps/plugins/mpegplayer/mpeg_settings.c
index bcef4c66bf..b5c9c6bbc8 100644
--- a/apps/plugins/mpegplayer/mpeg_settings.c
+++ b/apps/plugins/mpegplayer/mpeg_settings.c
@@ -677,8 +677,9 @@ static uint32_t increment_time(uint32_t val, int32_t amount, uint32_t range)
 }
 
 #if defined(HAVE_LCD_ENABLE) || defined(HAVE_LCD_SLEEP)
-static void get_start_time_lcd_enable_hook(void *param)
+static void get_start_time_lcd_enable_hook(unsigned short id, void *param)
 {
+    (void)id;
     (void)param;
     rb->queue_post(rb->button_queue, LCD_ENABLE_EVENT_0, 0);
 }
@@ -698,7 +699,7 @@ static int get_start_time(uint32_t duration)
     mylcd_update();
 
 #if defined(HAVE_LCD_ENABLE) || defined(HAVE_LCD_SLEEP)
-    rb->add_event(LCD_EVENT_ACTIVATION, false, get_start_time_lcd_enable_hook);
+    rb->add_event(LCD_EVENT_ACTIVATION, get_start_time_lcd_enable_hook);
 #endif
 
     draw_slider(0, 100, &rc_bound);
diff --git a/apps/plugins/mpegplayer/mpegplayer.c b/apps/plugins/mpegplayer/mpegplayer.c
index 928c48ab11..467c961912 100644
--- a/apps/plugins/mpegplayer/mpegplayer.c
+++ b/apps/plugins/mpegplayer/mpegplayer.c
@@ -1026,8 +1026,9 @@ static void fps_init(void)
 
 #if defined(HAVE_LCD_ENABLE) || defined(HAVE_LCD_SLEEP)
 /* So we can refresh the overlay */
-static void osd_lcd_enable_hook(void* param)
+static void osd_lcd_enable_hook(unsigned short id, void* param)
 {
+    (void)id;
     (void)param;
     rb->queue_post(rb->button_queue, LCD_ENABLE_EVENT_1, 0);
 }
@@ -1043,7 +1044,7 @@ static void osd_backlight_on_video_mode(bool video_on)
 #endif
     } else {
 #if defined(HAVE_LCD_ENABLE) || defined(HAVE_LCD_SLEEP)
-        rb->add_event(LCD_EVENT_ACTIVATION, false, osd_lcd_enable_hook);
+        rb->add_event(LCD_EVENT_ACTIVATION, osd_lcd_enable_hook);
 #endif
         /* Revert to user's backlight settings */
         backlight_use_settings();
diff --git a/apps/radio/radioart.c b/apps/radio/radioart.c
index 86a987c14f..283815167a 100644
--- a/apps/radio/radioart.c
+++ b/apps/radio/radioart.c
@@ -145,7 +145,7 @@ int radio_get_art_hid(struct dim *requested_dim)
     return -1;
 }
 
-static void buffer_reset_handler(void *data)
+static void buffer_reset_handler(unsigned short id, void *data, void *user_data)
 {
     buf = NULL;
     for(int i=0;i<MAX_RADIOART_IMAGES;i++)
@@ -156,7 +156,9 @@ static void buffer_reset_handler(void *data)
         radioart[i].name[0] = '\0';
     }
 
+    (void)id;
     (void)data;
+    (void)user_data;
 }
 
 static int shrink_callback(int handle, unsigned hints, void* start, size_t old_size)
@@ -183,7 +185,7 @@ static int shrink_callback(int handle, unsigned hints, void* start, size_t old_s
         buf = start;
 
         /* one-shot */
-        add_event(BUFFER_EVENT_BUFFER_RESET, true, buffer_reset_handler);
+        add_event_ex(BUFFER_EVENT_BUFFER_RESET, true, buffer_reset_handler, NULL);
     }
 
     return BUFLIB_CB_OK;
@@ -203,7 +205,7 @@ void radioart_init(bool entering_screen)
         buffering_reset(core_get_data(handle), bufsize);
         buf = core_get_data(handle);
         /* one-shot */
-        add_event(BUFFER_EVENT_BUFFER_RESET, true, buffer_reset_handler);
+        add_event_ex(BUFFER_EVENT_BUFFER_RESET, true, buffer_reset_handler, NULL);
     }
     else /* init at startup */
     {
diff --git a/apps/root_menu.c b/apps/root_menu.c
index 09c7efad9d..c94a4443e6 100644
--- a/apps/root_menu.c
+++ b/apps/root_menu.c
@@ -88,8 +88,9 @@ static int last_screen = GO_TO_ROOT; /* unfortunatly needed so we can resume
 
 
 static char current_track_path[MAX_PATH];
-static void rootmenu_track_changed_callback(void* param)
+static void rootmenu_track_changed_callback(unsigned short id, void* param)
 {
+    (void)id;
     struct mp3entry *id3 = ((struct track_event *)param)->id3;
     strlcpy(current_track_path, id3->path, MAX_PATH);
 }
@@ -746,7 +747,7 @@ void root_menu(void)
     if (global_settings.start_in_screen == 0)
         next_screen = (int)global_status.last_screen;
     else next_screen = global_settings.start_in_screen - 2;
-    add_event(PLAYBACK_EVENT_TRACK_CHANGE, false, rootmenu_track_changed_callback);
+    add_event(PLAYBACK_EVENT_TRACK_CHANGE, rootmenu_track_changed_callback);
 #ifdef HAVE_RTC_ALARM
     if ( rtc_check_alarm_started(true) )
     {
diff --git a/apps/scrobbler.c b/apps/scrobbler.c
index efd028327c..b8a95f85cb 100644
--- a/apps/scrobbler.c
+++ b/apps/scrobbler.c
@@ -150,9 +150,8 @@ static void write_cache(void)
     cache_pos = 0;
 }
 
-static void scrobbler_flush_callback(void *data)
+static void scrobbler_flush_callback(void)
 {
-    (void)data;
     if (scrobbler_initialised && cache_pos)
         write_cache();
 }
@@ -200,16 +199,17 @@ static void add_to_cache(const struct mp3entry *id)
 
 }
 
-static void scrobbler_change_event(void *data)
+static void scrobbler_change_event(unsigned short id, void *ev_data)
 {
-    struct mp3entry *id = ((struct track_event *)data)->id3;
+    (void)id;
+    struct mp3entry *id3 = ((struct track_event *)ev_data)->id3;
 
     /*  check if track was resumed > %50 played
         check for blank artist or track name */
-    if (id->elapsed > id->length / 2 || !id->artist || !id->title)
+    if (id3->elapsed > id3->length / 2 || !id3->artist || !id3->title)
     {
         pending = false;
-        logf("SCROBBLER: skipping file %s", id->path);
+        logf("SCROBBLER: skipping file %s", id3->path);
     }
     else
     {
@@ -219,8 +219,9 @@ static void scrobbler_change_event(void *data)
     }
 }
 
-static void scrobbler_finish_event(void *data)
+static void scrobbler_finish_event(unsigned short id, void *data)
 {
+    (void)id;
     struct track_event *te = (struct track_event *)data;
 
     /* add entry using the currently ending track */
@@ -254,8 +255,8 @@ int scrobbler_init(void)
 
     scrobbler_initialised = true;
 
-    add_event(PLAYBACK_EVENT_TRACK_CHANGE, false, scrobbler_change_event);
-    add_event(PLAYBACK_EVENT_TRACK_FINISH, false, scrobbler_finish_event);
+    add_event(PLAYBACK_EVENT_TRACK_CHANGE, scrobbler_change_event);
+    add_event(PLAYBACK_EVENT_TRACK_FINISH, scrobbler_finish_event);
 
     return 1;
 }
diff --git a/apps/settings.c b/apps/settings.c
index 58d58788be..f2a923e24d 100644
--- a/apps/settings.c
+++ b/apps/settings.c
@@ -591,15 +591,13 @@ static bool settings_write_config(const char* filename, int options)
     return true;
 }
 #ifndef HAVE_RTC_RAM
-static void flush_global_status_callback(void *data)
+static void flush_global_status_callback(void)
 {
-    (void)data;
     write_nvram_data(nvram_buffer,NVRAM_BLOCK_SIZE);
 }
 #endif
-static void flush_config_block_callback(void *data)
+static void flush_config_block_callback(void)
 {
-    (void)data;
     write_nvram_data(nvram_buffer,NVRAM_BLOCK_SIZE);
     settings_write_config(CONFIGFILE, SETTINGS_SAVE_CHANGED);
 }
@@ -1307,4 +1305,3 @@ void set_file(const char* filename, char* setting, const int maxlen)
     strlcpy(setting, fptr, len);
     settings_save();
 }
-
diff --git a/apps/shortcuts.c b/apps/shortcuts.c
index ee8454485d..a9ae8248f1 100644
--- a/apps/shortcuts.c
+++ b/apps/shortcuts.c
@@ -184,9 +184,8 @@ static void init_shortcut(struct shortcut* sc)
 
 static int first_idx_to_writeback = -1;
 static bool overwrite_shortcuts = false;
-static void shortcuts_ata_idle_callback(void* data)
+static void shortcuts_ata_idle_callback(void)
 {
-    (void)data;
     int fd;
     char buf[MAX_PATH];
     int current_idx = first_idx_to_writeback;
@@ -387,7 +386,7 @@ static int shortcut_menu_get_action(int action, struct gui_synclist *lists)
             gui_synclist_select_item(lists, shortcut_count - 1);
         first_idx_to_writeback = 0;
         overwrite_shortcuts = true;
-        shortcuts_ata_idle_callback(NULL);
+        shortcuts_ata_idle_callback();
         if (shortcut_count == 0)
             return ACTION_STD_CANCEL;
         return ACTION_REDRAW;
diff --git a/apps/tagcache.c b/apps/tagcache.c
index 3ce0247188..b7d5516e81 100644
--- a/apps/tagcache.c
+++ b/apps/tagcache.c
@@ -3195,9 +3195,8 @@ static bool command_queue_is_full(void)
     return (next == command_queue_ridx);
 }
 
-static void command_queue_sync_callback(void *data)
+static void command_queue_sync_callback(void)
 {
-    (void)data;
     struct master_header myhdr;
     int masterfd;
         
@@ -3246,7 +3245,7 @@ static void run_command_queue(bool force)
         return;
     
     if (force || command_queue_is_full())
-        command_queue_sync_callback(NULL);
+        command_queue_sync_callback();
     else
         register_storage_idle_func(command_queue_sync_callback);
 }
@@ -4898,4 +4897,3 @@ int tagcache_get_max_commit_step(void)
 {
     return (int)(SORTED_TAGS_COUNT)+1;
 }
-
diff --git a/apps/tagtree.c b/apps/tagtree.c
index ff364ec5e4..b3b94a489e 100644
--- a/apps/tagtree.c
+++ b/apps/tagtree.c
@@ -804,10 +804,11 @@ static int nat_compare(const void *p1, const void *p2)
     return strnatcasecmp(e1->name, e2->name);
 }
 
-static void tagtree_buffer_event(void *data)
+static void tagtree_buffer_event(unsigned short id, void *ev_data)
 {
+    (void)id;
     struct tagcache_search tcs;
-    struct mp3entry *id3 = ((struct track_event *)data)->id3;
+    struct mp3entry *id3 = ((struct track_event *)ev_data)->id3;
 
     bool runtimedb = global_settings.runtimedb;
     bool autoresume = global_settings.autoresume_enable;
@@ -868,9 +869,10 @@ static void tagtree_buffer_event(void *data)
     tagcache_search_finish(&tcs);
 }
 
-static void tagtree_track_finish_event(void *data)
+static void tagtree_track_finish_event(unsigned short id, void *ev_data)
 {
-    struct track_event *te = (struct track_event *)data;
+    (void)id;
+    struct track_event *te = (struct track_event *)ev_data;
     struct mp3entry *id3 = te->id3;
 
     long tagcache_idx = id3->tagcache_idx;
@@ -1183,8 +1185,8 @@ void tagtree_init(void)
     if (rootmenu < 0)
         rootmenu = 0;
 
-    add_event(PLAYBACK_EVENT_TRACK_BUFFER, false, tagtree_buffer_event);
-    add_event(PLAYBACK_EVENT_TRACK_FINISH, false, tagtree_track_finish_event);
+    add_event(PLAYBACK_EVENT_TRACK_BUFFER, tagtree_buffer_event);
+    add_event(PLAYBACK_EVENT_TRACK_FINISH, tagtree_track_finish_event);
 
     core_shrink(tagtree_handle, core_get_data(tagtree_handle), tagtree_buf_used);
 }
diff --git a/firmware/ata_idle_notify.c b/firmware/ata_idle_notify.c
index 35d192bee0..ee9f3c035f 100644
--- a/firmware/ata_idle_notify.c
+++ b/firmware/ata_idle_notify.c
@@ -25,12 +25,20 @@
 #include "kernel.h"
 #include "string.h"
 
-void register_storage_idle_func(void (*function)(void *data))
+static void wrapper(unsigned short id, void *ev_data, void *user_data)
+{
+    (void)id;
+    (void)ev_data;
+    void (*func)(void) = user_data;
+    func();
+}
+
+void register_storage_idle_func(void (*function)(void))
 {
 #if USING_STORAGE_CALLBACK
-    add_event(DISK_EVENT_SPINUP, true, function);
+    add_event_ex(DISK_EVENT_SPINUP, true, wrapper, function);
 #else
-    function(NULL); /* just call the function now */
+    function(); /* just call the function now */
 /* this _may_ cause problems later if the calling function
    sets a variable expecting the callback to unset it, because
    the callback will be run before this function exits, so before the var is set */
@@ -38,12 +46,12 @@ void register_storage_idle_func(void (*function)(void *data))
 }
 
 #if USING_STORAGE_CALLBACK
-void unregister_storage_idle_func(void (*func)(void *data), bool run)
+void unregister_storage_idle_func(void (*func)(void), bool run)
 {
-    remove_event(DISK_EVENT_SPINUP, func);
+    remove_event_ex(DISK_EVENT_SPINUP, wrapper, func);
     
     if (run)
-        func(NULL);
+        func();
 }
 
 bool call_storage_idle_notifys(bool force)
diff --git a/firmware/events.c b/firmware/events.c
index 74172e1fa0..4a51e7ae87 100644
--- a/firmware/events.c
+++ b/firmware/events.c
@@ -28,30 +28,41 @@
 struct sysevent {
     unsigned short id;
     bool oneshot;
-    void (*callback)(void *data);
+    bool has_user_data;
+    union {
+        void (*callback)(unsigned short id, void *event_data);
+        struct {
+            void (*callback2)(unsigned short id, void *event_data, void *user_data);
+            void *user_data;
+        };
+    } handler;
 };
 
 static struct sysevent events[MAX_SYS_EVENTS];
 
-bool add_event(unsigned short id, bool oneshot, void (*handler)(void *data))
+static bool do_add_event(unsigned short id, bool oneshot, bool user_data_valid,
+                         void *handler, void *user_data)
 {
     int i;
     
     /* Check if the event already exists. */
     for (i = 0; i < MAX_SYS_EVENTS; i++)
     {
-        if (events[i].callback == handler && events[i].id == id)
+        if (events[i].handler.callback == handler && events[i].id == id
+                && (!user_data_valid || (user_data == events[i].handler.callback)))
             return false;
     }
     
     /* Try to find a free slot. */
     for (i = 0; i < MAX_SYS_EVENTS; i++)
     {
-        if (events[i].callback == NULL)
+        if (events[i].handler.callback == NULL)
         {
             events[i].id = id;
             events[i].oneshot = oneshot;
-            events[i].callback = handler;
+            if ((events[i].has_user_data = user_data_valid))
+                events[i].handler.user_data = user_data;
+            events[i].handler.callback = handler;
             return true;
         }
     }
@@ -60,33 +71,59 @@ bool add_event(unsigned short id, bool oneshot, void (*handler)(void *data))
     return false;
 }
 
-void remove_event(unsigned short id, void (*handler)(void *data))
+bool add_event(unsigned short id, void (*handler)(unsigned short id, void *data))
+{
+    return do_add_event(id, false, false, handler, NULL);
+}
+
+bool add_event_ex(unsigned short id, bool oneshot, void (*handler)(unsigned short id, void *event_data, void *user_data), void *user_data)
+{
+    return do_add_event(id, oneshot, true, handler, user_data);
+}
+
+void do_remove_event(unsigned short id, bool user_data_valid,
+                  void *handler, void *user_data)
 {
     int i;
     
     for (i = 0; i < MAX_SYS_EVENTS; i++)
     {
-        if (events[i].id == id && events[i].callback == handler)
+        if (events[i].id == id && events[i].handler.callback == handler
+                && (!user_data_valid || (user_data == events[i].handler.callback)))
         {
-            events[i].callback = NULL;
+            events[i].handler.callback = NULL;
             return;
         }
     }
 }
 
+void remove_event(unsigned short id, void (*handler)(unsigned short id, void *data))
+{
+    do_remove_event(id, false, handler, NULL);
+}
+
+void remove_event_ex(unsigned short id,
+                     void (*handler)(unsigned short id, void *event_data, void *user_data),
+                     void *user_data)
+{
+    do_remove_event(id, true, handler, user_data);
+}
+
 void send_event(unsigned short id, void *data)
 {
     int i;
     
     for (i = 0; i < MAX_SYS_EVENTS; i++)
     {
-        if (events[i].id == id && events[i].callback != NULL)
+        if (events[i].id == id && events[i].handler.callback != NULL)
         {
-            events[i].callback(data);
+            if (events[i].has_user_data)
+                events[i].handler.callback2(id, data, events[i].handler.user_data);
+            else
+                events[i].handler.callback(id, data);
             
             if (events[i].oneshot)
-                events[i].callback = NULL;
+                events[i].handler.callback = NULL;
         }
     }
 }
-
diff --git a/firmware/export/ata_idle_notify.h b/firmware/export/ata_idle_notify.h
index 93a53eee34..0443f8e516 100644
--- a/firmware/export/ata_idle_notify.h
+++ b/firmware/export/ata_idle_notify.h
@@ -48,9 +48,9 @@ enum {
  */
 #define USING_STORAGE_CALLBACK  !defined(BOOTLOADER) && !defined(APPLICATION) && !defined(__PCTOOL__)
 
-extern void register_storage_idle_func(void (*function)(void *data));
+extern void register_storage_idle_func(void (*function)(void));
 #if USING_STORAGE_CALLBACK
-extern void unregister_storage_idle_func(void (*function)(void *data), bool run);
+extern void unregister_storage_idle_func(void (*function)(void), bool run);
 extern bool call_storage_idle_notifys(bool force);
 #else
 #define unregister_storage_idle_func(f,r)
diff --git a/firmware/export/events.h b/firmware/export/events.h
index 859901c0b4..fd7f9df42e 100644
--- a/firmware/export/events.h
+++ b/firmware/export/events.h
@@ -23,12 +23,24 @@
 #define _EVENTS_H
 
 #include <stdbool.h>
-
-/** Only CLASS defines and firmware/ level events should be defined here.
- *  apps/ level events are defined in apps/appevents.h 
- */
-
 /**
+ * Synchronouos event system.
+ *
+ * Callbacks are subscribed with add_event() or add_event_ex(). events
+ * are fired using send_event().
+ *
+ * Events are always dispatched synchronously: the callbacks are called
+ * in the thread context of the event sender, without context switch. This
+ * also means that callbacks should be as simple as possible to avoid
+ * blocking the sender and other callbacks
+ *
+ * Use the kernel-level event_queue for cross-thread event dispatching.
+ * */
+
+/*
+ * Only CLASS defines and firmware/ level events should be defined here.
+ * apps/ level events are defined in apps/appevents.h
+ * 
  * High byte = Event class definition
  * Low byte  = Event ID
  */
@@ -40,9 +52,50 @@
 #define EVENT_CLASS_RECORDING  0x1000
 #define EVENT_CLASS_LCD        0x2000
 
-bool add_event(unsigned short id, bool oneshot, void (*handler)(void *data));
-void remove_event(unsigned short id, void (*handler)(void *data));
+/**
+ * Subscribe to an event with a simple callback. The callback will be called
+ * synchronously everytime the event fires, passing the event id and data to
+ * the callback.
+ *
+ * Must be removed with remove_event(). 
+ */
+bool add_event(unsigned short id, void (*handler)(unsigned short id, void *event_data));
+
+/**
+ * Subscribe to an event with a detailed callback. The callback will be called
+ * synchronously everytime the event fires, passing the event id and data, as
+ * well as the user_data pointer passed here, to the callback.
+ *
+ * With oneshot == true, the callback is unsubscribed automatically after
+ * the event fired for the first time. In this case the event need not to be
+ * removed with remove_event_ex().
+ *
+ * Must be removed with remove_event_ex(). remove_event() will never remove
+ * events added with this function. 
+ */
+bool add_event_ex(unsigned short id, bool oneshot, void (*handler)(unsigned short id, void *event_data, void *user_data), void *user_data);
+
+/**
+ * Unsubscribe a callback from an event. The handler pointer is matched.
+ *
+ * This will only work for subscriptions made with add_event().
+ */
+void remove_event(unsigned short id, void (*handler)(unsigned short id, void *data));
+
+/**
+ * Unsubscribe a callback from an event. The handler and user_data pointers
+ * are matched. That means the same user_data that was passed to add_event_ex()
+ * must be passed to this too.
+ *
+ * This will only work for subscriptions made with add_event_ex().
+ */
+void remove_event_ex(unsigned short id, void (*handler)(unsigned short id, void *event_data, void *user_data), void *user_data);
+
+/**
+ * Fire an event, which synchronously calls all subscribed callbacks. The
+ * event id and data pointer are passed to the callbacks as well, and
+ * optionally the user_data pointer from add_event_ex().
+ */
 void send_event(unsigned short id, void *data);
 
 #endif
-
diff --git a/firmware/logf.c b/firmware/logf.c
index a24a635570..ade5458ca9 100644
--- a/firmware/logf.c
+++ b/firmware/logf.c
@@ -322,7 +322,7 @@ static int logdiskf_push(void *userp, unsigned char c)
     return true;
 }
 
-static void flush_buffer(void* data);
+static void flush_buffer(void);
 
 void _logdiskf(const char* file, const char level, const char *fmt, ...)
 {
@@ -350,9 +350,8 @@ void _logdiskf(const char* file, const char level, const char *fmt, ...)
     register_storage_idle_func(flush_buffer);
 }
 
-static void flush_buffer(void* data)
+static void flush_buffer(void)
 {
-    (void)data;
     int fd;
     if(logdiskfindex < 1)
         return;