acp: Don't sync hardware volumes while UCM device is disabled

The hardware controls we track for volume and mute state can change as
part of enabling or disabling the UCM device. This then triggers a
re-sync of our state with the hardware controls, which can e.g. set our
volume to an unwanted value as the result of enabling the device, or set
a hardware control to a wrong value based on our volume while disabling
the device. So these UCM-triggered changes to enable/disable the device
will at best show up on user interfaces and cause confusion, but maybe
even will push the hardware into an unexpected state.

The volume and mute state we set from user interfaces only make sense
when the devices are enabled. They should not be kept in sync with
hardware for inactive UCM devices [1]. Skip the callbacks for reading
and changing volume and mute state if the UCM device is disabled. This
way, the volume/mute controls for sinks/sources are essentially detached
from the hardware controls until the UCM device is re-enabled.

[1] https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/772#note_1872757

Link: https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/772
Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

spa/plugins/alsa/acp/acp.c

@@ -1143,6 +1143,14 @@ static int read_volume(pa_alsa_device *dev)
 	uint32_t i;
 	int res;
 
+	if (dev->ucm_context) {
+		if (!dev->active_port)
+			return 0;
+		pa_alsa_ucm_port_data *data = PA_DEVICE_PORT_DATA(dev->active_port);
+		if (pa_alsa_ucm_port_device_status(data) <= 0)
+			return 0;
+	}
+
 	if (!dev->mixer_handle)
 		return 0;
 
@@ -1178,6 +1186,14 @@ static void set_volume(pa_alsa_device *dev, const pa_cvolume *v)
 	if (v != &dev->real_volume)
 		dev->real_volume = *v;
 
+	if (dev->ucm_context) {
+		if (!dev->active_port)
+			return;
+		pa_alsa_ucm_port_data *data = PA_DEVICE_PORT_DATA(dev->active_port);
+		if (pa_alsa_ucm_port_device_status(data) <= 0)
+			return;
+	}
+
 	if (!dev->mixer_handle)
 		return;
 
@@ -1231,6 +1247,14 @@ static int read_mute(pa_alsa_device *dev)
 	bool mute;
 	int res;
 
+	if (dev->ucm_context) {
+		if (!dev->active_port)
+			return 0;
+		pa_alsa_ucm_port_data *data = PA_DEVICE_PORT_DATA(dev->active_port);
+		if (pa_alsa_ucm_port_device_status(data) <= 0)
+			return 0;
+	}
+
 	if (!dev->mixer_handle)
 		return 0;
 
@@ -1253,6 +1277,14 @@ static void set_mute(pa_alsa_device *dev, bool mute)
 {
 	dev->muted = mute;
 
+	if (dev->ucm_context) {
+		if (!dev->active_port)
+			return;
+		pa_alsa_ucm_port_data *data = PA_DEVICE_PORT_DATA(dev->active_port);
+		if (pa_alsa_ucm_port_device_status(data) <= 0)
+			return;
+	}
+
 	if (!dev->mixer_handle)
 		return;
 

spa/plugins/alsa/acp/alsa-ucm.c

@@ -2559,6 +2559,10 @@ static void ucm_port_data_free(pa_device_port *port) {
     pa_xfree(ucm_port->eld_mixer_device_name);
 }
 
+long pa_alsa_ucm_port_device_status(pa_alsa_ucm_port_data *data) {
+    return ucm_device_status(data->ucm, data->device);
+}
+
 #else /* HAVE_ALSA_UCM */
 
 /* Dummy functions for systems without UCM support */
@@ -2615,4 +2619,8 @@ void pa_alsa_ucm_roled_stream_begin(pa_alsa_ucm_config *ucm, const char *role, p
 void pa_alsa_ucm_roled_stream_end(pa_alsa_ucm_config *ucm, const char *role, pa_direction_t dir) {
 }
 
+long pa_alsa_ucm_port_device_status(pa_alsa_ucm_port_data *data) {
+    return -1;
+}
+
 #endif

spa/plugins/alsa/acp/alsa-ucm.h

@@ -292,6 +292,8 @@ struct pa_alsa_ucm_port_data {
     int eld_device; /* PCM device number */
 };
 
+long pa_alsa_ucm_port_device_status(pa_alsa_ucm_port_data *data);
+
 struct pa_alsa_ucm_volume {
     char *mixer_elem;	/* mixer element identifier */
     char *master_elem;	/* master mixer element identifier */