janus: plug audio devices dynamically

janus/src/acap.c

@@ -47,19 +47,6 @@ static void *_pcm_thread(void *v_acap);
 static void *_encoder_thread(void *v_acap);
 
 
-bool us_acap_probe(const char *name) {
-	snd_pcm_t *dev;
-	int err;
-	US_JLOG_INFO("acap", "Probing PCM capture ...");
-	if ((err = snd_pcm_open(&dev, name, SND_PCM_STREAM_CAPTURE, 0)) < 0) {
-		US_JLOG_PERROR_ALSA(err, "acap", "Can't probe PCM capture");
-		return false;
-	}
-	snd_pcm_close(dev);
-	US_JLOG_INFO("acap", "PCM capture is available");
-	return true;
-}
-
 us_acap_s *us_acap_init(const char *name, uint pcm_hz) {
 	us_acap_s *acap;
 	US_CALLOC(acap, 1);

janus/src/acap.h

@@ -53,8 +53,6 @@ typedef struct {
 } us_acap_s;
 
 
-bool us_acap_probe(const char *name);
-
 us_acap_s *us_acap_init(const char *name, uint pcm_hz);
 void us_acap_destroy(us_acap_s *acap);
 

janus/src/au.c

@@ -23,10 +23,78 @@
 #include "au.h"
 
 #include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+#include <sys/stat.h>
 
 #include "uslibs/tools.h"
 
 
+bool us_au_probe(const char *name) {
+	// This function is very limited. It takes something like:
+	//   hw:0,0 or hw:tc358743,0 or plughw:UAC2Gadget,0
+	// parses card name (0, tc358743, UAC2Gadget) and checks
+	// the existence of it in /proc/asound/.
+	// It's enough for our case.
+
+	if (name == NULL) {
+		return false;
+	}
+
+	if (strchr(name, '/') || strchr(name, '.')) {
+		return false;
+	}
+
+	const char *begin = strchr(name, ':');
+	if (begin == NULL) {
+		return false;
+	}
+	begin += 1;
+	if (*begin == '\0') {
+		return false;
+	}
+
+	const char *end = strchr(begin, ',');
+	if (end == NULL) {
+		return false;
+	}
+	if (end - begin < 1) {
+		return false;
+	}
+
+	char *card = us_strdup(begin);
+	card[end - begin] = '\0';
+
+	bool numeric = true;
+	for (uz index = 0; card[index] != '\0'; ++index) {
+		if (!isdigit(card[index])) {
+			numeric = false;
+			break;
+		}
+	}
+
+	char *path;
+	if (numeric) {
+		US_ASPRINTF(path, "/proc/asound/card%s", card);
+	} else {
+		US_ASPRINTF(path, "/proc/asound/%s", card);
+	}
+
+	bool ok = false;
+	struct stat st;
+	if (lstat(path, &st) == 0) {
+		if (numeric && S_ISDIR(st.st_mode)) {
+			ok = true;
+		} else if (!numeric && S_ISLNK(st.st_mode)) {
+			ok = true;
+		}
+	}
+	free(path);
+	free(card);
+	return ok;
+}
+
 us_au_pcm_s *us_au_pcm_init(void) {
 	us_au_pcm_s *pcm;
 	US_CALLOC(pcm, 1);

janus/src/au.h

@@ -51,6 +51,7 @@ typedef struct {
 	u64		pts;
 } us_au_encoded_s;
 
+bool us_au_probe(const char *name);
 
 us_au_pcm_s *us_au_pcm_init(void);
 void us_au_pcm_destroy(us_au_pcm_s *pcm);

janus/src/plugin.c

@@ -69,7 +69,7 @@ static us_janus_client_s	*_g_clients = NULL;
 static janus_callbacks		*_g_gw = NULL;
 static us_ring_s			*_g_video_ring = NULL;
 static us_rtpv_s			*_g_rtpv = NULL;
-static us_rtpa_s			*_g_rtpa = NULL; // Also indicates "audio capture is available"
+static us_rtpa_s			*_g_rtpa = NULL;
 
 static pthread_t		_g_video_rtp_tid;
 static atomic_bool		_g_video_rtp_tid_created = false;
@@ -250,6 +250,10 @@ static void *_acap_thread(void *arg) {
 		uint hz = 0;
 		us_acap_s *acap = NULL;
 
+		if (!us_au_probe(_g_config->acap_dev_name)) {
+			US_ONCE({ US_JLOG_ERROR("acap", "No PCM capture device"); });
+			goto close_acap;
+		}
 		if (_check_tc358743_acap(&hz) < 0) {
 			goto close_acap;
 		}
@@ -339,6 +343,11 @@ static void *_aplay_thread(void *arg) {
 			}
 
 			if (dev == NULL) {
+				if (!us_au_probe(_g_config->aplay_dev_name)) {
+					US_ONCE({ US_JLOG_ERROR("aplay", "No PCM playback device"); });
+					goto close_aplay;
+				}
+
 				int err = snd_pcm_open(&dev, _g_config->aplay_dev_name, SND_PCM_STREAM_PLAYBACK, 0);
 				if (err < 0) {
 					US_ONCE({ US_JLOG_PERROR_ALSA(err, "aplay", "Can't open PCM playback"); });
@@ -424,7 +433,7 @@ static int _plugin_init(janus_callbacks *gw, const char *config_dir_path) {
 
 	US_RING_INIT_WITH_ITEMS(_g_video_ring, 64, us_frame_init);
 	_g_rtpv = us_rtpv_init(_relay_rtp_clients);
-	if (_g_config->acap_dev_name != NULL && us_acap_probe(_g_config->acap_dev_name)) {
+	if (_g_config->acap_dev_name != NULL) {
 		_g_rtpa = us_rtpa_init(_relay_rtp_clients);
 		US_THREAD_CREATE(_g_acap_tid, _acap_thread, NULL);
 		if (_g_config->aplay_dev_name != NULL) {
@@ -602,13 +611,13 @@ static struct janus_plugin_result *_plugin_handle_message(
 				{
 					json_t *const obj = json_object_get(params, "audio");
 					if (obj != NULL && json_is_boolean(obj)) {
-						with_acap = (_g_rtpa != NULL && json_boolean_value(obj));
+						with_acap = (us_au_probe(_g_config->acap_dev_name) && json_boolean_value(obj));
 					}
 				}
 				{
 					json_t *const obj = json_object_get(params, "mic");
 					if (obj != NULL && json_is_boolean(obj)) {
-						with_aplay = (_g_config->aplay_dev_name != NULL && with_acap && json_boolean_value(obj));
+						with_aplay = (us_au_probe(_g_config->aplay_dev_name) && json_boolean_value(obj));
 					}
 				}
 				{
@@ -673,10 +682,11 @@ static struct janus_plugin_result *_plugin_handle_message(
 
 	} else if (!strcmp(request_str, "features")) {
 		const char *const ice_url = getenv("JANUS_USTREAMER_WEB_ICE_URL");
+		const bool acap_avail = us_au_probe(_g_config->acap_dev_name);
 		json_t *const features = json_pack(
 			"{s:b, s:b, s:{s:s?}}",
-			"audio", (_g_rtpa != NULL),
+			"audio", acap_avail,
-			"mic", (_g_rtpa != NULL && _g_config->aplay_dev_name != NULL),
+			"mic", (acap_avail && us_au_probe(_g_config->aplay_dev_name)),
 			"ice", "url", (ice_url != NULL ? ice_url : default_ice_url)
 		);
 		PUSH_STATUS("features", features, NULL);