Modify player-to-DACP status update communication

Have DACP set a callback (through a sync_command() setter) into the player
instead of setting an fd without any locking. All the code now lies in DACP
instead of being split between DACP and the player.

src/httpd_dacp.c

@@ -342,6 +342,25 @@ playstatusupdate_cb(int fd, short what, void *arg)
     DPRINTF(E_LOG, L_DACP, "Couldn't re-add event for playstatusupdate\n");
 }
 
+/* Thread: player */
+static void
+dacp_playstatus_update_handler(void)
+{
+  int ret;
+
+#ifdef USE_EVENTFD
+  ret = eventfd_write(update_efd, 1);
+  if (ret < 0)
+    DPRINTF(E_LOG, L_DACP, "Could not send status update event: %s\n", strerror(errno));
+#else
+  int dummy = 42;
+
+  ret = write(update_pipe[1], &dummy, sizeof(dummy));
+  if (ret != sizeof(dummy))
+    DPRINTF(E_LOG, L_DACP, "Could not write to status update fd: %s\n", strerror(errno));
+#endif
+}
+
 static void
 update_fail_cb(struct evhttp_connection *evcon, void *arg)
 {
@@ -1794,11 +1813,7 @@ dacp_init(void)
   event_base_set(evbase_httpd, &updateev);
   event_add(&updateev, NULL);
 
-#ifdef USE_EVENTFD
-  player_set_updatefd(update_efd);
-#else
-  player_set_updatefd(update_pipe[1]);
-#endif
+  player_set_update_handler(dacp_playstatus_update_handler);
 
   return 0;
 
@@ -1823,6 +1838,8 @@ dacp_deinit(void)
   struct dacp_update_request *ur;
   int i;
 
+  player_set_update_handler(NULL);
+
   for (i = 0; dacp_handlers[i].handler; i++)
     regfree(&dacp_handlers[i].preg);
 
@@ -1839,8 +1856,6 @@ dacp_deinit(void)
       free(ur);
     }
 
-  player_set_updatefd(-1);
-
   event_del(&updateev);
 
   avl_free_tree(dacp_props_hash);

src/player.c

@@ -129,7 +129,7 @@ static enum repeat_mode repeat;
 static char shuffle;
 
 /* Status updates (for DACP) */
-static int update_fd;
+static player_status_handler update_handler;
 
 /* Playback timer */
 static int pb_timer_fd;
@@ -181,26 +181,10 @@ static struct evbuffer *audio_buf;
 static void
 status_update(enum play_status status)
 {
-#ifndef USE_EVENTFD
-  int dummy = 42;
-#endif
-  int ret;
-
   player_state = status;
 
-  if (update_fd < 0)
-    return;
-
-#ifdef USE_EVENTFD
-  ret = eventfd_write(update_fd, 1);
-  if (ret < 0)
-#else
-  ret = write(update_fd, &dummy, sizeof(dummy));
-  if (ret != sizeof(dummy))
-#endif
-    {
-      DPRINTF(E_LOG, L_PLAYER, "Could not send status update: %s\n", strerror(errno));
-    }
+  if (update_handler)
+    update_handler();
 }
 
 
@@ -2467,6 +2451,17 @@ queue_plid(void *arg)
   return 0;
 }
 
+static int
+set_update_handler(void *arg)
+{
+  player_status_handler handler;
+
+  handler = (player_status_handler)arg;
+
+  update_handler = handler;
+
+  return 0;
+}
 
 /* Command helpers */
 /* Thread: player */
@@ -2842,6 +2837,19 @@ player_queue_plid(uint32_t plid)
   pthread_mutex_unlock(&cmd_lck);
 }
 
+void
+player_set_update_handler(player_status_handler handler)
+{
+  pthread_mutex_lock(&cmd_lck);
+
+  cmd.func = set_update_handler;
+  cmd.func_bh = NULL;
+  cmd.arg = handler;
+
+  sync_command();
+
+  pthread_mutex_unlock(&cmd_lck);
+}
 
 /* Thread: main (mdns) */
 static void
@@ -3176,13 +3184,6 @@ exit_cb(int fd, short what, void *arg)
   player_exit = 1;
 }
 
-/* Thread: main at DACP init/deinit */
-void
-player_set_updatefd(int fd)
-{
-  update_fd = fd;
-}
-
 /* Thread: main */
 int
 player_init(void)
@@ -3212,7 +3213,7 @@ player_init(void)
   repeat = REPEAT_OFF;
   shuffle = 0;
 
-  update_fd = -1;
+  update_handler = NULL;
 
   /* Random RTP time start */
   gcry_randomize(&rnd, sizeof(rnd), GCRY_STRONG_RANDOM);

src/player.h

@@ -46,6 +46,7 @@ struct player_status {
 };
 
 typedef void (*spk_enum_cb)(uint64_t id, const char *name, int selected, int has_password, void *arg);
+typedef void (*player_status_handler)(void);
 
 struct player_source;
 
@@ -112,7 +113,7 @@ player_queue_plid(uint32_t plid);
 
 
 void
-player_set_updatefd(int fd);
+player_set_update_handler(player_status_handler handler);
 
 int
 player_init(void);