ao: make better use of atomics

The main reason for this was compatibility; but some associated problems
have been solved in the previous commit.

(cherry picked from commit ca9964a4fb)

audio/out/ao.c

@@ -385,28 +385,26 @@ bool ao_eof_reached(struct ao *ao)
 // Query the AO_EVENT_*s as requested by the events parameter, and return them.
 int ao_query_and_reset_events(struct ao *ao, int events)
 {
-    int actual_events = 0;
-    if (atomic_load(&ao->request_reload)) // don't need to reset it
-        actual_events |= AO_EVENT_RELOAD;
-    if (atomic_load(&ao->request_hotplug))
-        actual_events |= AO_EVENT_HOTPLUG;
-    return actual_events & events;
+    return atomic_fetch_and(&ao->events_, ~(unsigned)events) & events;
+}
+
+static void ao_add_events(struct ao *ao, int events)
+{
+    atomic_fetch_or(&ao->events_, events);
+    if (ao->input_ctx)
+        mp_input_wakeup(ao->input_ctx);
 }
 
 // Request that the player core destroys and recreates the AO. Fully thread-safe.
 void ao_request_reload(struct ao *ao)
 {
-    atomic_store(&ao->request_reload, true);
-    if (ao->input_ctx)
-        mp_input_wakeup(ao->input_ctx);
+    ao_add_events(ao, AO_EVENT_RELOAD);
 }
 
 // Notify the player that the device list changed. Fully thread-safe.
 void ao_hotplug_event(struct ao *ao)
 {
-    atomic_store(&ao->request_hotplug, true);
-    if (ao->input_ctx)
-        mp_input_wakeup(ao->input_ctx);
+    ao_add_events(ao, AO_EVENT_HOTPLUG);
 }
 
 bool ao_chmap_sel_adjust(struct ao *ao, const struct mp_chmap_sel *s,
@@ -503,7 +501,6 @@ bool ao_hotplug_check_update(struct ao_hotplug *hp)
 {
     if (hp->ao && ao_query_and_reset_events(hp->ao, AO_EVENT_HOTPLUG)) {
         hp->needs_update = true;
-        atomic_store(&hp->ao->request_hotplug, false);
         return true;
     }
     return false;

audio/out/internal.h

@@ -59,7 +59,7 @@ struct ao {
     char *redirect;
 
     // Internal events (use ao_request_reload(), ao_hotplug_event())
-    atomic_bool request_reload, request_hotplug;
+    atomic_int events_;
 
     int buffer;
     double def_buffer;

osdep/atomics.h

@@ -34,6 +34,7 @@
 
 typedef struct { volatile unsigned long v, t;       } atomic_ulong;
 typedef struct { volatile int v, t;                 } atomic_int;
+typedef struct { volatile unsigned int v, t;        } atomic_uint;
 typedef struct { volatile _Bool v, t;               } atomic_bool;
 typedef struct { volatile long long v, t;           } atomic_llong;
 typedef struct { volatile uint_least32_t v, t;      } atomic_uint_least32_t;