jack alsa: implement restart request [3/3]

in case ALSA_DRIVER_FEAT_LINK_DEVS is defined, driver will attempt to
snd_pcm_link all devices

Change-Id: I7bd54b8414d0b614786bee1078667a9aa595b58f
Signed-off-by: Adam Miartus <amiartus@de.adit-jv.com>
(cherry picked from commit da45a136f5)
Signed-off-by: Timo Wischer <twischer@de.adit-jv.com>

linux/alsa/JackAlsaDriver.cpp

@@ -863,6 +863,9 @@ SERVER_EXPORT const jack_driver_desc_t* driver_get_descriptor ()
     value.i = 0;
     jack_driver_descriptor_add_parameter(desc, &filler, "close-idle-devs", 'c', JackDriverParamBool, &value, NULL, "Close idle devices on alsa driver restart request", NULL);
 
+    value.i = 0;
+    jack_driver_descriptor_add_parameter(desc, &filler, "unlinked-devs", 'u', JackDriverParamBool, &value, NULL, "Do not link devices", NULL);
+
     return desc;
 }
 
@@ -1053,6 +1056,9 @@ SERVER_EXPORT Jack::JackDriverClientInterface* driver_initialize(Jack::JackLocke
                 info.features |= param->value.i ? ALSA_DRIVER_FEAT_CLOSE_IDLE_DEVS : 0;
                 break;
 
+            case 'u':
+                info.features |= param->value.i ? ALSA_DRIVER_FEAT_UNLINKED_DEVS : 0;
+                break;
         }
     }
 

linux/alsa/alsa_driver.c

@@ -1415,6 +1415,81 @@ alsa_driver_open (alsa_driver_t *driver)
 		}
 	}
 
+	if (driver->features & ALSA_DRIVER_FEAT_UNLINKED_DEVS) {
+		jack_info ("alsa driver linking disabled");
+		return 0;
+	} else {
+		jack_info ("alsa driver linking enabled");
+	}
+
+	snd_pcm_t *group_handle = NULL;
+
+	for (int i = 0; i < driver->devices_c_count; ++i) {
+		alsa_device_t *device = &driver->devices[i];
+
+		if (!device->capture_handle) {
+			continue;
+		}
+
+		if (device->capture_target_state != SND_PCM_STATE_RUNNING) {
+			continue;
+		}
+
+		if (group_handle == NULL) {
+			group_handle = device->capture_handle;
+			device->capture_linked = 1;
+			continue;
+		}
+
+		if (device->capture_linked) {
+			continue;
+		}
+
+		if (group_handle == device->capture_handle) {
+			device->capture_linked = 1;
+			continue;
+		}
+
+		if (snd_pcm_link (group_handle, device->capture_handle) != 0) {
+			jack_error ("failed to add device to link group C: '%s'", device->capture_name);
+			continue;
+		}
+		device->capture_linked = 1;
+	}
+
+	for (int i = 0; i < driver->devices_p_count; ++i) {
+		alsa_device_t *device = &driver->devices[i];
+
+		if (!device->playback_handle) {
+			continue;
+		}
+
+		if (device->playback_target_state != SND_PCM_STATE_RUNNING) {
+			continue;
+		}
+
+		if (group_handle == NULL) {
+			group_handle = device->playback_handle;
+			device->playback_linked = 1;
+			continue;
+		}
+
+		if (device->playback_linked) {
+			continue;
+		}
+
+		if (group_handle == device->playback_handle) {
+			device->playback_linked = 1;
+			continue;
+		}
+
+		if (snd_pcm_link (group_handle, device->playback_handle) != 0) {
+			jack_error ("failed to add device to link group P: '%s'", device->playback_name);
+			continue;
+		}
+		device->playback_linked = 1;
+	}
+
 	return 0;
 }
 
@@ -1446,6 +1521,13 @@ alsa_driver_start (alsa_driver_t *driver)
 		}
 
 		driver->capture_nfds += snd_pcm_poll_descriptors_count (device->capture_handle);
+
+		if (group_done && device->capture_linked) {
+			continue;
+		}
+
+		if (device->capture_linked) {
+			group_done = 1;
 		}
 
 		if ((err = alsa_driver_prepare (device->capture_handle, SND_PCM_STREAM_CAPTURE)) < 0) {
@@ -1467,6 +1549,14 @@ alsa_driver_start (alsa_driver_t *driver)
 
 		driver->playback_nfds += snd_pcm_poll_descriptors_count (device->playback_handle);
 
+		if (group_done && device->playback_linked) {
+			continue;
+		}
+
+		if (device->playback_linked) {
+			group_done = 1;
+		}
+
 		if ((err = alsa_driver_prepare (device->playback_handle, SND_PCM_STREAM_PLAYBACK)) < 0) {
 			jack_error ("ALSA: failed to prepare device '%s' (%s)", device->playback_name, snd_strerror(err));
 			return -1;
@@ -1558,6 +1648,8 @@ alsa_driver_start (alsa_driver_t *driver)
 #endif
 	}
 
+	group_done = 0;
+
 	for (int i = 0; i < driver->devices_c_count; ++i) {
 		alsa_device_t *device = &driver->devices[i];
 
@@ -1569,6 +1661,14 @@ alsa_driver_start (alsa_driver_t *driver)
 			continue;
 		}
 
+		if (group_done && device->capture_linked) {
+			continue;
+		}
+
+		if (device->capture_linked) {
+			group_done = 1;
+		}
+
 		if ((err = alsa_driver_stream_start (device->capture_handle, SND_PCM_STREAM_CAPTURE)) < 0) {
 			jack_error ("ALSA: failed to start device C: '%s' (%s)", device->capture_name,
 					snd_strerror(err));
@@ -1587,6 +1687,14 @@ alsa_driver_start (alsa_driver_t *driver)
 			continue;
 		}
 
+		if (group_done && device->playback_linked) {
+			continue;
+		}
+
+		if (device->playback_linked) {
+			group_done = 1;
+		}
+
 		if ((err = alsa_driver_stream_start (device->playback_handle, SND_PCM_STREAM_PLAYBACK)) < 0) {
 			jack_error ("ALSA: failed to start device P: '%s' (%s)", device->playback_name,
 					snd_strerror(err));
@@ -1626,6 +1734,7 @@ alsa_driver_stop (alsa_driver_t *driver)
 // JACK2
     ClearOutput();
 
+	int group_done = 0;
 
 	for (int i = 0; i < driver->devices_c_count; ++i) {
 		alsa_device_t *device = &driver->devices[i];
@@ -1633,6 +1742,14 @@ alsa_driver_stop (alsa_driver_t *driver)
 			continue;
 		}
 
+		if (group_done && device->capture_linked) {
+			continue;
+		}
+
+		if (device->capture_linked) {
+			group_done = 1;
+		}
+
 #ifdef __QNXNTO__
 		/* In case of capture: Flush discards the frames */
 		err = snd_pcm_plugin_flush(device->capture_handle, SND_PCM_CHANNEL_CAPTURE);
@@ -1651,6 +1768,14 @@ alsa_driver_stop (alsa_driver_t *driver)
 			continue;
 		}
 
+		if (group_done && device->playback_linked) {
+			continue;
+		}
+
+		if (device->playback_linked) {
+			group_done = 1;
+		}
+
 #ifdef __QNXNTO__
 		/* In case of playback: Drain discards the frames */
 		err = snd_pcm_plugin_playback_drain(device->playback_handle);
@@ -1683,6 +1808,11 @@ alsa_driver_close (alsa_driver_t *driver)
 			continue;
 		}
 
+		if (device->capture_linked) {
+			snd_pcm_unlink(device->capture_handle);
+			device->capture_linked = 0;
+		}
+
 		snd_pcm_close(device->capture_handle);
 		device->capture_handle = NULL;
 	}
@@ -1693,6 +1823,11 @@ alsa_driver_close (alsa_driver_t *driver)
 			continue;
 		}
 
+		if (device->playback_linked) {
+			snd_pcm_unlink(device->playback_handle);
+			device->playback_linked = 0;
+		}
+
 		snd_pcm_close(device->playback_handle);
 		device->playback_handle = NULL;
 	}

linux/alsa/alsa_driver.h

@@ -70,6 +70,7 @@ typedef int32_t                    alsa_driver_default_format_t;
 #endif
 
 #define ALSA_DRIVER_FEAT_CLOSE_IDLE_DEVS   (1 << 1)
+#define ALSA_DRIVER_FEAT_UNLINKED_DEVS     (1 << 2)
 
 #ifdef __cplusplus
 extern "C"