audio: change internal device listing API

Now we run ao_driver->list_devs on a dummy AO instance, which will
probably confuse everyone. This is done for the sake of PulseAudio.

audio/out/ao.c

@@ -152,11 +152,8 @@ static bool match_ao_driver(const char *ao_name, char *opt, char **out_device)
     return true;
 }
 
-static struct ao *ao_create(bool probing, struct mpv_global *global,
-                            struct input_ctx *input_ctx,
-                            struct encode_lavc_context *encode_lavc_ctx,
-                            int samplerate, int format, struct mp_chmap channels,
-                            char *name, char **args)
+static struct ao *ao_alloc(bool probing, struct mpv_global *global,
+                           struct input_ctx *input_ctx, char *name, char **args)
 {
     struct MPOpts *opts = global->opts;
     struct mp_log *log = mp_log_new(NULL, global->log, "ao");
@@ -171,22 +168,36 @@ static struct ao *ao_create(bool probing, struct mpv_global *global,
     *ao = (struct ao) {
         .driver = desc.p,
         .probing = probing,
-        .encode_lavc_ctx = encode_lavc_ctx,
         .input_ctx = input_ctx,
-        .samplerate = samplerate,
-        .channels = channels,
-        .format = format,
         .log = mp_log_new(ao, log, name),
         .def_buffer = opts->audio_buffer,
     };
-    if (ao->driver->encode != !!ao->encode_lavc_ctx)
-        goto error;
     struct m_config *config = m_config_from_obj_desc(ao, ao->log, &desc);
     if (m_config_apply_defaults(config, name, opts->ao_defs) < 0)
         goto error;
     if (m_config_set_obj_params(config, args) < 0)
         goto error;
     ao->priv = config->optstruct;
+    return ao;
+error:
+    talloc_free(ao);
+    return NULL;
+}
+
+static struct ao *ao_create(bool probing, struct mpv_global *global,
+                            struct input_ctx *input_ctx,
+                            struct encode_lavc_context *encode_lavc_ctx,
+                            int samplerate, int format, struct mp_chmap channels,
+                            char *name, char **args)
+{
+    struct MPOpts *opts = global->opts;
+    struct ao *ao = ao_alloc(probing, global, input_ctx, name, args);
+    ao->samplerate = samplerate;
+    ao->channels = channels;
+    ao->format = format;
+    ao->encode_lavc_ctx = encode_lavc_ctx;
+    if (ao->driver->encode != !!ao->encode_lavc_ctx)
+        goto error;
 
     match_ao_driver(ao->driver->name, opts->audio_device, &ao->device);
     ao->device = talloc_strdup(ao, ao->device);
@@ -388,34 +399,39 @@ bool ao_untimed(struct ao *ao)
     return ao->untimed;
 }
 
-struct ao_device_list *ao_get_device_list(void)
+struct ao_device_list *ao_get_device_list(struct mpv_global *global)
 {
     struct ao_device_list *list = talloc_zero(NULL, struct ao_device_list);
     for (int n = 0; audio_out_drivers[n]; n++) {
         const struct ao_driver *d = audio_out_drivers[n];
+        struct ao *ao = ao_alloc(true, global, NULL, (char *)d->name, NULL);
+        if (!ao)
+            continue;
         int num = list->num_devices;
         if (d->list_devs)
-            d->list_devs(d, list);
+            d->list_devs(ao, list);
         // Add at least a default entry
         if (list->num_devices == num)
-            ao_device_list_add(list, d, &(struct ao_device_desc){"", ""});
+            ao_device_list_add(list, ao, &(struct ao_device_desc){"", ""});
+        talloc_free(ao);
     }
     return list;
 }
 
-void ao_device_list_add(struct ao_device_list *list, const struct ao_driver *d,
+void ao_device_list_add(struct ao_device_list *list, struct ao *ao,
                         struct ao_device_desc *e)
 {
     struct ao_device_desc c = *e;
-    c.name = c.name[0] ? talloc_asprintf(list, "%s/%s", d->name, c.name)
-                       : talloc_strdup(list, d->name);
+    const char *dname = ao->driver->name;
+    c.name = c.name[0] ? talloc_asprintf(list, "%s/%s", dname, c.name)
+                       : talloc_strdup(list, dname);
     c.desc = talloc_strdup(list, c.desc);
     MP_TARRAY_APPEND(list, list->devices, list->num_devices, c);
 }
 
-void ao_print_devices(struct mp_log *log)
+void ao_print_devices(struct mpv_global *global, struct mp_log *log)
 {
-    struct ao_device_list *list = ao_get_device_list();
+    struct ao_device_list *list = ao_get_device_list(global);
     mp_info(log, "List of detected audio devices:\n");
     for (int n = 0; n < list->num_devices; n++) {
         struct ao_device_desc *desc = &list->devices[n];

audio/out/ao.h

@@ -52,8 +52,8 @@ typedef struct ao_control_vol {
 } ao_control_vol_t;
 
 struct ao_device_desc {
-    char *name;     // symbolic name; will be set on ao->device
-    char *desc;     // verbose human readable name
+    const char *name;   // symbolic name; will be set on ao->device
+    const char *desc;   // verbose human readable name
 };
 
 struct ao_device_list {
@@ -86,7 +86,7 @@ void ao_resume(struct ao *ao);
 void ao_drain(struct ao *ao);
 bool ao_eof_reached(struct ao *ao);
 
-struct ao_device_list *ao_get_device_list(void);
-void ao_print_devices(struct mp_log *log);
+struct ao_device_list *ao_get_device_list(struct mpv_global *global);
+void ao_print_devices(struct mpv_global *global, struct mp_log *log);
 
 #endif /* MPLAYER_AUDIO_OUT_H */

audio/out/ao_alsa.c

@@ -733,7 +733,7 @@ alsa_error:
     return -1;
 }
 
-static void list_devs(const struct ao_driver *d, struct ao_device_list *list)
+static void list_devs(struct ao *ao, struct ao_device_list *list)
 {
     void **hints;
     if (snd_device_name_hint(-1, "pcm", &hints) < 0)
@@ -751,7 +751,7 @@ static void list_devs(const struct ao_driver *d, struct ao_device_list *list)
             if (desc2[i] == '\n')
                 desc2[i] = '/';
         }
-        ao_device_list_add(list, d, &(struct ao_device_desc){name, desc2});
+        ao_device_list_add(list, ao, &(struct ao_device_desc){name, desc2});
     }
 
     snd_device_name_free_hint(hints);

audio/out/internal.h

@@ -149,7 +149,16 @@ struct ao_driver {
     // Return the list of devices currently available in the system. Use
     // ao_device_list_add() to add entries. The selected device will be set as
     // ao->device (using ao_device_desc.name).
-    void (*list_devs)(const struct ao_driver *d, struct ao_device_list *list);
+    // Warning: the ao struct passed doesn't necessarily have ao_driver->init()
+    //          called on it - in this case, ->uninit() won't be called either
+    //          after this function. The idea is that list_devs can be called
+    //          both when no audio or when audio is active. the latter can
+    //          happen if the audio config change at runtime, and in this case
+    //          we don't want to force a new connection to the audio server
+    //          just to update the device list. For runtime updates, ->init()
+    //          will have been called. In both cases, ao->priv is properly
+    //          allocated. (Runtime updates are not used/supported yet.)
+    void (*list_devs)(struct ao *ao, struct ao_device_list *list);
 
     // For option parsing (see vo.h)
     int priv_size;
@@ -172,7 +181,8 @@ bool ao_chmap_sel_get_def(struct ao *ao, const struct mp_chmap_sel *s,
                           struct mp_chmap *map, int num);
 
 // Add a deep copy of e to the list.
-void ao_device_list_add(struct ao_device_list *list, const struct ao_driver *d,
+// Call from ao_driver->list_devs callback only.
+void ao_device_list_add(struct ao_device_list *list, struct ao *ao,
                         struct ao_device_desc *e);
 
 #endif

player/main.c

@@ -232,7 +232,7 @@ static bool handle_help_options(struct MPContext *mpctx)
         opt_exit = 1;
     }
     if (opts->audio_device && strcmp(opts->audio_device, "help") == 0) {
-        ao_print_devices(log);
+        ao_print_devices(mpctx->global, log);
         opt_exit = 1;
     }
 #if HAVE_ENCODING