Allow read-only or non-existing sink input volume.

There are two known cases where read-only or non-existing sink input volume is
relevant: passthrough streams and the planned volume sharing logic.
Passthrough streams don't have volume at all, and the volume sharing logic
requires read-only sink input volume. This commit is primarily working towards
the volume sharing feature, but support for non-existing sink input volume is
also added, because it is so closely related to read-only volume.

Some unrelated refactoring in iface-stream.c creeped into this commit too (new
function: stream_to_string()).

PROTOCOL

@@ -203,7 +203,13 @@ new flag at end of CREATE_PLAYBACK_STREAM:
 
 ## v19, implemented by >= 0.9.22
 
-New proplist field for sink input, source output introspection opcodes and at the end:
+New flag at the end of sink input and source output introspection data:
 
     bool corked
 
+## v20, implemented by >= 1.0
+
+Two new flags at the end of sink input introspection data:
+
+    bool has_volume
+    bool read_only_volume

src/modules/dbus/iface-stream.c

@@ -56,6 +56,9 @@ struct pa_dbusiface_stream {
     dbus_bool_t mute;
     pa_proplist *proplist;
 
+    pa_bool_t has_volume;
+    pa_bool_t read_only_volume;
+
     pa_dbus_protocol *dbus_protocol;
     pa_subscription *subscription;
     pa_hook_slot *send_event_slot;
@@ -189,6 +192,14 @@ static void handle_get_index(DBusConnection *conn, DBusMessage *msg, void *userd
     pa_dbus_send_basic_variant_reply(conn, msg, DBUS_TYPE_UINT32, &idx);
 }
 
+/* The returned string has to be freed with pa_xfree() by the caller. */
+static char *stream_to_string(pa_dbusiface_stream *s) {
+    if (s->type == STREAM_TYPE_PLAYBACK)
+        return pa_sprintf_malloc("Playback stream %u", (unsigned) s->sink_input->index);
+    else
+        return pa_sprintf_malloc("Record stream %u", (unsigned) s->source_output->index);
+}
+
 static void handle_get_driver(DBusConnection *conn, DBusMessage *msg, void *userdata) {
     pa_dbusiface_stream *s = userdata;
     const char *driver = NULL;
@@ -200,12 +211,11 @@ static void handle_get_driver(DBusConnection *conn, DBusMessage *msg, void *user
     driver = (s->type == STREAM_TYPE_PLAYBACK) ? s->sink_input->driver : s->source_output->driver;
 
     if (!driver) {
-        if (s->type == STREAM_TYPE_PLAYBACK)
+        char *str = stream_to_string(s);
-            pa_dbus_send_error(conn, msg, PA_DBUS_ERROR_NO_SUCH_PROPERTY,
+
-                               "Playback stream %u doesn't have a driver.", s->sink_input->index);
+        pa_dbus_send_error(conn, msg, PA_DBUS_ERROR_NO_SUCH_PROPERTY, "%s doesn't have a driver.", str);
-        else
+        pa_xfree(str);
-            pa_dbus_send_error(conn, msg, PA_DBUS_ERROR_NO_SUCH_PROPERTY,
+
-                               "Record stream %u doesn't have a driver.", s->source_output->index);
         return;
     }
 
@@ -224,12 +234,11 @@ static void handle_get_owner_module(DBusConnection *conn, DBusMessage *msg, void
     owner_module = (s->type == STREAM_TYPE_PLAYBACK) ? s->sink_input->module : s->source_output->module;
 
     if (!owner_module) {
-        if (s->type == STREAM_TYPE_PLAYBACK)
+        char *str = stream_to_string(s);
-            pa_dbus_send_error(conn, msg, PA_DBUS_ERROR_NO_SUCH_PROPERTY,
+
-                               "Playback stream %u doesn't have an owner module.", s->sink_input->index);
+        pa_dbus_send_error(conn, msg, PA_DBUS_ERROR_NO_SUCH_PROPERTY, "%s doesn't have an owner module.", str);
-        else
+        pa_xfree(str);
-            pa_dbus_send_error(conn, msg, PA_DBUS_ERROR_NO_SUCH_PROPERTY,
+
-                               "Record stream %u doesn't have an owner module.", s->source_output->index);
         return;
     }
 
@@ -250,12 +259,11 @@ static void handle_get_client(DBusConnection *conn, DBusMessage *msg, void *user
     client = (s->type == STREAM_TYPE_PLAYBACK) ? s->sink_input->client : s->source_output->client;
 
     if (!client) {
-        if (s->type == STREAM_TYPE_PLAYBACK)
+        char *str = stream_to_string(s);
-            pa_dbus_send_error(conn, msg, PA_DBUS_ERROR_NO_SUCH_PROPERTY,
+
-                               "Playback stream %u isn't associated to any client.", s->sink_input->index);
+        pa_dbus_send_error(conn, msg, PA_DBUS_ERROR_NO_SUCH_PROPERTY, "%s isn't associated to any client.", str);
-        else
+        pa_xfree(str);
-            pa_dbus_send_error(conn, msg, PA_DBUS_ERROR_NO_SUCH_PROPERTY,
+
-                               "Record stream %u isn't associated to any client.", s->source_output->index);
         return;
     }
 
@@ -332,8 +340,12 @@ static void handle_get_volume(DBusConnection *conn, DBusMessage *msg, void *user
     pa_assert(msg);
     pa_assert(s);
 
-    if (s->type == STREAM_TYPE_RECORD) {
+    if (!s->has_volume) {
-        pa_dbus_send_error(conn, msg, PA_DBUS_ERROR_NO_SUCH_PROPERTY, "Record streams don't have volume.");
+        char *str = stream_to_string(s);
+
+        pa_dbus_send_error(conn, msg, PA_DBUS_ERROR_NO_SUCH_PROPERTY, "%s doesn't have volume.", str);
+        pa_xfree(str);
+
         return;
     }
 
@@ -357,8 +369,15 @@ static void handle_set_volume(DBusConnection *conn, DBusMessage *msg, DBusMessag
     pa_assert(iter);
     pa_assert(s);
 
-    if (s->type == STREAM_TYPE_RECORD) {
+    if (!s->has_volume || s->read_only_volume) {
-        pa_dbus_send_error(conn, msg, PA_DBUS_ERROR_NO_SUCH_PROPERTY, "Record streams don't have volume.");
+        char *str = stream_to_string(s);
+
+        if (!s->has_volume)
+            pa_dbus_send_error(conn, msg, PA_DBUS_ERROR_NO_SUCH_PROPERTY, "%s doesn't have volume.", str);
+        else if (s->read_only_volume)
+            pa_dbus_send_error(conn, msg, DBUS_ERROR_ACCESS_DENIED, "%s has read-only volume.", str);
+        pa_xfree(str);
+
         return;
     }
 
@@ -509,6 +528,11 @@ static void handle_get_all(DBusConnection *conn, DBusMessage *msg, void *userdat
     pa_assert(msg);
     pa_assert(s);
 
+    if (s->has_volume) {
+        for (i = 0; i < s->volume.channels; ++i)
+            volume[i] = s->volume.values[i];
+    }
+
     if (s->type == STREAM_TYPE_PLAYBACK) {
         idx = s->sink_input->index;
         driver = s->sink_input->driver;
@@ -517,8 +541,6 @@ static void handle_get_all(DBusConnection *conn, DBusMessage *msg, void *userdat
         device = pa_dbusiface_core_get_sink_path(s->core, s->sink);
         sample_format = s->sink_input->sample_spec.format;
         channel_map = &s->sink_input->channel_map;
-        for (i = 0; i < s->volume.channels; ++i)
-            volume[i] = s->volume.values[i];
         buffer_latency = pa_sink_input_get_latency(s->sink_input, &device_latency);
         resample_method = pa_resample_method_to_string(s->sink_input->actual_resample_method);
     } else {
@@ -560,7 +582,7 @@ static void handle_get_all(DBusConnection *conn, DBusMessage *msg, void *userdat
     pa_dbus_append_basic_variant_dict_entry(&dict_iter, property_handlers[PROPERTY_HANDLER_SAMPLE_RATE].property_name, DBUS_TYPE_UINT32, &s->sample_rate);
     pa_dbus_append_basic_array_variant_dict_entry(&dict_iter, property_handlers[PROPERTY_HANDLER_CHANNELS].property_name, DBUS_TYPE_UINT32, channels, channel_map->channels);
 
-    if (s->type == STREAM_TYPE_PLAYBACK) {
+    if (s->has_volume) {
         pa_dbus_append_basic_array_variant_dict_entry(&dict_iter, property_handlers[PROPERTY_HANDLER_VOLUME].property_name, DBUS_TYPE_UINT32, volume, s->volume.channels);
         pa_dbus_append_basic_variant_dict_entry(&dict_iter, property_handlers[PROPERTY_HANDLER_MUTE].property_name, DBUS_TYPE_BOOLEAN, &s->mute);
     }
@@ -708,30 +730,33 @@ static void subscription_cb(pa_core *c, pa_subscription_event_type_t t, uint32_t
     }
 
     if (s->type == STREAM_TYPE_PLAYBACK) {
-        pa_cvolume new_volume;
         pa_bool_t new_mute = FALSE;
 
-        pa_sink_input_get_volume(s->sink_input, &new_volume, TRUE);
+        if (s->has_volume) {
+            pa_cvolume new_volume;
 
-        if (!pa_cvolume_equal(&s->volume, &new_volume)) {
+            pa_sink_input_get_volume(s->sink_input, &new_volume, TRUE);
-            dbus_uint32_t volume[PA_CHANNELS_MAX];
-            dbus_uint32_t *volume_ptr = volume;
 
-            s->volume = new_volume;
+            if (!pa_cvolume_equal(&s->volume, &new_volume)) {
+                dbus_uint32_t volume[PA_CHANNELS_MAX];
+                dbus_uint32_t *volume_ptr = volume;
 
-            for (i = 0; i < s->volume.channels; ++i)
+                s->volume = new_volume;
-                volume[i] = s->volume.values[i];
 
-            pa_assert_se(signal_msg = dbus_message_new_signal(s->path,
+                for (i = 0; i < s->volume.channels; ++i)
-							      PA_DBUSIFACE_STREAM_INTERFACE,
+                    volume[i] = s->volume.values[i];
-							      signals[SIGNAL_VOLUME_UPDATED].name));
-            pa_assert_se(dbus_message_append_args(signal_msg,
-                                                  DBUS_TYPE_ARRAY, DBUS_TYPE_UINT32, &volume_ptr, s->volume.channels,
-                                                  DBUS_TYPE_INVALID));
 
-            pa_dbus_protocol_send_signal(s->dbus_protocol, signal_msg);
+                pa_assert_se(signal_msg = dbus_message_new_signal(s->path,
-            dbus_message_unref(signal_msg);
+                                                                  PA_DBUSIFACE_STREAM_INTERFACE,
-            signal_msg = NULL;
+                                                                  signals[SIGNAL_VOLUME_UPDATED].name));
+                pa_assert_se(dbus_message_append_args(signal_msg,
+                                                      DBUS_TYPE_ARRAY, DBUS_TYPE_UINT32, &volume_ptr, s->volume.channels,
+                                                      DBUS_TYPE_INVALID));
+
+                pa_dbus_protocol_send_signal(s->dbus_protocol, signal_msg);
+                dbus_message_unref(signal_msg);
+                signal_msg = NULL;
+            }
         }
 
         new_mute = pa_sink_input_get_mute(s->sink_input);
@@ -823,7 +848,14 @@ pa_dbusiface_stream *pa_dbusiface_stream_new_playback(pa_dbusiface_core *core, p
     s->path = pa_sprintf_malloc("%s/%s%u", PA_DBUS_CORE_OBJECT_PATH, PLAYBACK_OBJECT_NAME, sink_input->index);
     s->sink = pa_sink_ref(sink_input->sink);
     s->sample_rate = sink_input->sample_spec.rate;
-    pa_sink_input_get_volume(sink_input, &s->volume, TRUE);
+    s->has_volume = pa_sink_input_is_volume_readable(sink_input);
+    s->read_only_volume = s->has_volume ? !pa_sink_input_is_volume_writable(sink_input) : FALSE;
+
+    if (s->has_volume)
+        pa_sink_input_get_volume(sink_input, &s->volume, TRUE);
+    else
+        pa_cvolume_init(&s->volume);
+
     s->mute = pa_sink_input_get_mute(sink_input);
     s->proplist = pa_proplist_copy(sink_input->proplist);
     s->dbus_protocol = pa_dbus_protocol_get(sink_input->core);
@@ -854,6 +886,8 @@ pa_dbusiface_stream *pa_dbusiface_stream_new_record(pa_dbusiface_core *core, pa_
     pa_cvolume_init(&s->volume);
     s->mute = FALSE;
     s->proplist = pa_proplist_copy(source_output->proplist);
+    s->has_volume = FALSE;
+    s->read_only_volume = FALSE;
     s->dbus_protocol = pa_dbus_protocol_get(source_output->core);
     s->subscription = pa_subscription_new(source_output->core, PA_SUBSCRIPTION_MASK_SOURCE_OUTPUT, subscription_cb, s);
     s->send_event_slot = pa_hook_connect(&source_output->core->hooks[PA_CORE_HOOK_SOURCE_OUTPUT_SEND_EVENT],

src/modules/module-stream-restore.c

@@ -1168,6 +1168,8 @@ static void subscribe_callback(pa_core *c, pa_subscription_event_type_t t, uint3
         }
 
         if (sink_input->save_volume) {
+            pa_assert(pa_sink_input_is_volume_writable(sink_input));
+
             entry.channel_map = sink_input->channel_map;
             pa_sink_input_get_volume(sink_input, &entry.volume, FALSE);
             entry.volume_valid = TRUE;
@@ -1327,8 +1329,11 @@ static pa_hook_result_t sink_input_fixate_hook_callback(pa_core *c, pa_sink_inpu
     if ((e = read_entry(u, name))) {
 
         if (u->restore_volume && e->volume_valid) {
-
+            if (!pa_sink_input_new_data_is_volume_writable(new_data))
-            if (!new_data->volume_is_set) {
+                pa_log_debug("Not restoring volume for sink input %s, because its volume can't be changed.", name);
+            else if (new_data->volume_is_set)
+                pa_log_debug("Not restoring volume for sink input %s, because already set.", name);
+            else {
                 pa_cvolume v;
 
                 pa_log_info("Restoring volume for sink input %s.", name);
@@ -1339,8 +1344,7 @@ static pa_hook_result_t sink_input_fixate_hook_callback(pa_core *c, pa_sink_inpu
 
                 new_data->volume_is_absolute = FALSE;
                 new_data->save_volume = TRUE;
-            } else
+            }
-                pa_log_debug("Not restoring volume for sink input %s, because already set.", name);
         }
 
         if (u->restore_muted && e->muted_valid) {
@@ -1615,7 +1619,7 @@ static void apply_entry(struct userdata *u, const char *name, struct entry *e) {
         }
         pa_xfree(n);
 
-        if (u->restore_volume && e->volume_valid) {
+        if (u->restore_volume && e->volume_valid && pa_sink_input_is_volume_writable(si)) {
             pa_cvolume v;
 
             v = e->volume;

src/pulse/introspect.h

@@ -503,6 +503,8 @@ typedef struct pa_sink_input_info {
     int mute;                            /**< Stream muted \since 0.9.7 */
     pa_proplist *proplist;               /**< Property list \since 0.9.11 */
     int corked;                          /**< Stream corked \since 1.0 */
+    int has_volume;                      /**< Stream has volume. If not set, then the meaning of this struct's volume member is unspecified. \since 1.0 */
+    int read_only_volume;                /**< Stream volume can only be read. Although volume control is disabled, the stream volume is still not necessarily constant. \since 1.0 */
 } pa_sink_input_info;
 
 /** Callback prototype for pa_context_get_sink_input_info() and friends*/

src/pulsecore/cli-command.c

@@ -579,11 +579,16 @@ static int pa_cli_command_sink_input_volume(pa_core *c, pa_tokenizer *t, pa_strb
         return -1;
     }
 
-    if (!(si = pa_idxset_get_by_index(c->sink_inputs, (uint32_t) idx))) {
+    if (!(si = pa_idxset_get_by_index(c->sink_inputs, idx))) {
         pa_strbuf_puts(buf, "No sink input found with this index.\n");
         return -1;
     }
 
+    if (!pa_sink_input_is_volume_writable(si)) {
+        pa_strbuf_puts(buf, "This sink input's volume can't be changed.\n");
+        return -1;
+    }
+
     pa_cvolume_set(&cvolume, 1, volume);
     pa_sink_input_set_volume(si, &cvolume, TRUE, TRUE);
     return 0;

src/pulsecore/cli-text.c

@@ -553,8 +553,7 @@ char *pa_sink_input_list_to_string(pa_core *c) {
         pa_usec_t cl;
         const char *cmn;
         pa_cvolume v;
-
+        char *volume_str = NULL;
-        pa_sink_input_get_volume(i, &v, TRUE);
 
         cmn = pa_channel_map_to_pretty_name(&i->channel_map);
 
@@ -565,6 +564,15 @@ char *pa_sink_input_list_to_string(pa_core *c) {
 
         pa_assert(i->sink);
 
+        if (pa_sink_input_is_volume_readable(i)) {
+            pa_sink_input_get_volume(i, &v, TRUE);
+            volume_str = pa_sprintf_malloc("%s\n\t        %s\n\t        balance %0.2f",
+                                           pa_cvolume_snprint(cv, sizeof(cv), &v),
+                                           pa_sw_cvolume_snprint_dB(cvdb, sizeof(cvdb), &v),
+                                           pa_cvolume_get_balance(&v, &i->channel_map));
+        } else
+            volume_str = pa_xstrdup("n/a");
+
         pa_strbuf_printf(
             s,
             "    index: %u\n"
@@ -573,8 +581,6 @@ char *pa_sink_input_list_to_string(pa_core *c) {
             "\tstate: %s\n"
             "\tsink: %u <%s>\n"
             "\tvolume: %s\n"
-            "\t        %s\n"
-            "\t        balance %0.2f\n"
             "\tmuted: %s\n"
             "\tcurrent latency: %0.2f ms\n"
             "\trequested latency: %s\n"
@@ -596,9 +602,7 @@ char *pa_sink_input_list_to_string(pa_core *c) {
             i->flags & PA_SINK_INPUT_KILL_ON_SUSPEND ? "KILL_ON_SUSPEND " : "",
             state_table[pa_sink_input_get_state(i)],
             i->sink->index, i->sink->name,
-            pa_cvolume_snprint(cv, sizeof(cv), &v),
+            volume_str,
-            pa_sw_cvolume_snprint_dB(cvdb, sizeof(cvdb), &v),
-            pa_cvolume_get_balance(&v, &i->channel_map),
             pa_yes_no(pa_sink_input_get_mute(i)),
             (double) pa_sink_input_get_latency(i, NULL) / PA_USEC_PER_MSEC,
             clt,
@@ -608,6 +612,8 @@ char *pa_sink_input_list_to_string(pa_core *c) {
             cmn ? cmn : "",
             pa_resample_method_to_string(pa_sink_input_get_resample_method(i)));
 
+        pa_xfree(volume_str);
+
         if (i->module)
             pa_strbuf_printf(s, "\tmodule: %u\n", i->module->index);
         if (i->client)

src/pulsecore/protocol-native.c

@@ -3056,12 +3056,19 @@ static void sink_input_fill_tagstruct(pa_native_connection *c, pa_tagstruct *t,
     pa_sample_spec fixed_ss;
     pa_usec_t sink_latency;
     pa_cvolume v;
+    pa_bool_t has_volume = FALSE;
 
     pa_assert(t);
     pa_sink_input_assert_ref(s);
 
     fixup_sample_spec(c, &fixed_ss, &s->sample_spec);
 
+    has_volume = pa_sink_input_is_volume_readable(s);
+    if (has_volume)
+        pa_sink_input_get_volume(s, &v, TRUE);
+    else
+        pa_cvolume_reset(&v, fixed_ss.channels);
+
     pa_tagstruct_putu32(t, s->index);
     pa_tagstruct_puts(t, pa_strnull(pa_proplist_gets(s->proplist, PA_PROP_MEDIA_NAME)));
     pa_tagstruct_putu32(t, s->module ? s->module->index : PA_INVALID_INDEX);
@@ -3069,7 +3076,7 @@ static void sink_input_fill_tagstruct(pa_native_connection *c, pa_tagstruct *t,
     pa_tagstruct_putu32(t, s->sink->index);
     pa_tagstruct_put_sample_spec(t, &fixed_ss);
     pa_tagstruct_put_channel_map(t, &s->channel_map);
-    pa_tagstruct_put_cvolume(t, pa_sink_input_get_volume(s, &v, TRUE));
+    pa_tagstruct_put_cvolume(t, &v);
     pa_tagstruct_put_usec(t, pa_sink_input_get_latency(s, &sink_latency));
     pa_tagstruct_put_usec(t, sink_latency);
     pa_tagstruct_puts(t, pa_resample_method_to_string(pa_sink_input_get_resample_method(s)));
@@ -3080,6 +3087,10 @@ static void sink_input_fill_tagstruct(pa_native_connection *c, pa_tagstruct *t,
         pa_tagstruct_put_proplist(t, s->proplist);
     if (c->version >= 19)
         pa_tagstruct_put_boolean(t, (pa_sink_input_get_state(s) == PA_SINK_INPUT_CORKED));
+    if (c->version >= 20) {
+        pa_tagstruct_put_boolean(t, has_volume);
+        pa_tagstruct_put_boolean(t, has_volume ? !pa_sink_input_is_volume_writable(s) : FALSE);
+    }
 }
 
 static void source_output_fill_tagstruct(pa_native_connection *c, pa_tagstruct *t, pa_source_output *s) {
@@ -3461,6 +3472,7 @@ static void command_set_volume(
         pa_log_debug("Client %s changes volume of source %s.", client_name, source->name);
         pa_source_set_volume(source, &volume, TRUE);
     } else if (si) {
+        CHECK_VALIDITY(c->pstream, pa_sink_input_is_volume_writable(si), tag, PA_ERR_INVALID);
         CHECK_VALIDITY(c->pstream, volume.channels == 1 || pa_cvolume_compatible(&volume, &si->sample_spec), tag, PA_ERR_INVALID);
 
         pa_log_debug("Client %s changes volume of sink input %s.",

src/pulsecore/sink-input.c

@@ -112,8 +112,15 @@ void pa_sink_input_new_data_set_channel_map(pa_sink_input_new_data *data, const
         data->channel_map = *map;
 }
 
+pa_bool_t pa_sink_input_new_data_is_volume_writable(pa_sink_input_new_data *data) {
+    pa_assert(data);
+
+    return !(data->flags & PA_SINK_INPUT_PASSTHROUGH);
+}
+
 void pa_sink_input_new_data_set_volume(pa_sink_input_new_data *data, const pa_cvolume *volume) {
     pa_assert(data);
+    pa_assert(pa_sink_input_new_data_is_volume_writable(data));
 
     if ((data->volume_is_set = !!volume))
         data->volume = *volume;
@@ -205,6 +212,7 @@ int pa_sink_input_new(
     if ((r = pa_hook_fire(&core->hooks[PA_CORE_HOOK_SINK_INPUT_NEW], data)) < 0)
         return r;
 
+    pa_assert(!data->volume_is_set || pa_sink_input_new_data_is_volume_writable(data));
     pa_return_val_if_fail(!data->driver || pa_utf8_valid(data->driver), -PA_ERR_INVALID);
 
     if (!data->sink) {
@@ -1058,13 +1066,24 @@ static void set_real_ratio(pa_sink_input *i, const pa_cvolume *v) {
     /* We don't copy the data to the thread_info data. That's left for someone else to do */
 }
 
+/* Called from main context */
+pa_bool_t pa_sink_input_is_volume_readable(pa_sink_input *i) {
+    pa_sink_input_assert_ref(i);
+    pa_assert_ctl_context();
+
+    return !(i->flags & PA_SINK_INPUT_PASSTHROUGH);
+}
+
+/* Called from main context */
+pa_bool_t pa_sink_input_is_volume_writable(pa_sink_input *i) {
+    pa_sink_input_assert_ref(i);
+    pa_assert_ctl_context();
+
+    return !(i->flags & PA_SINK_INPUT_PASSTHROUGH);
+}
+
 /* Called from main context */
 void pa_sink_input_set_volume(pa_sink_input *i, const pa_cvolume *volume, pa_bool_t save, pa_bool_t absolute) {
-
-    /* Do not allow for volume changes for non-audio types */
-    if (i->flags & PA_SINK_INPUT_PASSTHROUGH)
-        return;
-
     /* test ramping -> return pa_sink_input_set_volume_with_ramping(i, volume, save, absolute, 2000 * PA_USEC_PER_MSEC); */
     return pa_sink_input_set_volume_with_ramping(i, volume, save, absolute, 0);
 }
@@ -1074,6 +1093,7 @@ pa_cvolume *pa_sink_input_get_volume(pa_sink_input *i, pa_cvolume *volume, pa_bo
     pa_sink_input_assert_ref(i);
     pa_assert_ctl_context();
     pa_assert(PA_SINK_INPUT_IS_LINKED(i->state));
+    pa_assert(pa_sink_input_is_volume_readable(i));
 
     if (absolute || !(i->sink->flags & PA_SINK_FLAT_VOLUME))
         *volume = i->volume;
@@ -1854,6 +1874,7 @@ void pa_sink_input_set_volume_with_ramping(pa_sink_input *i, const pa_cvolume *v
     pa_assert(volume);
     pa_assert(pa_cvolume_valid(volume));
     pa_assert(volume->channels == 1 || pa_cvolume_compatible(volume, &i->sample_spec));
+    pa_assert(pa_sink_input_is_volume_writable(i));
 
     if ((i->sink->flags & PA_SINK_FLAT_VOLUME) && !absolute) {
         v = i->sink->reference_volume;

src/pulsecore/sink-input.h

@@ -312,6 +312,7 @@ typedef struct pa_sink_input_new_data {
 pa_sink_input_new_data* pa_sink_input_new_data_init(pa_sink_input_new_data *data);
 void pa_sink_input_new_data_set_sample_spec(pa_sink_input_new_data *data, const pa_sample_spec *spec);
 void pa_sink_input_new_data_set_channel_map(pa_sink_input_new_data *data, const pa_channel_map *map);
+pa_bool_t pa_sink_input_new_data_is_volume_writable(pa_sink_input_new_data *data);
 void pa_sink_input_new_data_set_volume(pa_sink_input_new_data *data, const pa_cvolume *volume);
 void pa_sink_input_new_data_apply_volume_factor(pa_sink_input_new_data *data, const pa_cvolume *volume_factor);
 void pa_sink_input_new_data_apply_volume_factor_sink(pa_sink_input_new_data *data, const pa_cvolume *volume_factor);
@@ -356,6 +357,8 @@ void pa_sink_input_kill(pa_sink_input*i);
 
 pa_usec_t pa_sink_input_get_latency(pa_sink_input *i, pa_usec_t *sink_latency);
 
+pa_bool_t pa_sink_input_is_volume_readable(pa_sink_input *i);
+pa_bool_t pa_sink_input_is_volume_writable(pa_sink_input *i);
 void pa_sink_input_set_volume(pa_sink_input *i, const pa_cvolume *volume, pa_bool_t save, pa_bool_t absolute);
 pa_cvolume *pa_sink_input_get_volume(pa_sink_input *i, pa_cvolume *volume, pa_bool_t absolute);