alsa driver: Provide option to enable time stamp mode

for all devices.

This is required for example for some adaptive sample rate converters
which are executed on top of JACK. These SRCs are using the time stamp to
calculate the buffer fill level between playback application and sound
card.

Signed-off-by: Timo Wischer <twischer@de.adit-jv.com>

linux/alsa/JackAlsaDriver.cpp

@@ -279,7 +279,8 @@ int JackAlsaDriver::Open(jack_nframes_t nframes,
                          const char* playback_driver_name,
                          jack_nframes_t capture_latency,
                          jack_nframes_t playback_latency,
-                         const char* midi_driver_name)
+                         const char* midi_driver_name,
+                         int hw_timestamping)
 {
     // Generic JackAudioDriver Open
     if (JackAudioDriver::Open(nframes, samplerate, capturing, playing,
@@ -339,7 +340,8 @@ int JackAlsaDriver::Open(jack_nframes_t nframes,
                                shorts_first,
                                capture_latency,
                                playback_latency,
-                               midi);
+                               midi,
+                               hw_timestamping);
     if (fDriver) {
         // ALSA driver may have changed the in/out values
         fCaptureChannels = ((alsa_driver_t *)fDriver)->capture_nchannels;
@@ -750,6 +752,9 @@ SERVER_EXPORT const jack_driver_desc_t* driver_get_descriptor ()
         "ALSA MIDI driver",
         NULL);
 
+    value.i = 0;
+    jack_driver_descriptor_add_parameter(desc, &filler, "htstamps", 't', JackDriverParamBool, &value, NULL, "Enable htimestamping for the ALSA devices", NULL);
+
     return desc;
 }
 
@@ -777,6 +782,7 @@ SERVER_EXPORT Jack::JackDriverClientInterface* driver_initialize(Jack::JackLocke
     const JSList * node;
     const jack_driver_param_t * param;
     const char *midi_driver = "none";
+    int hw_timestamping = FALSE;
 
     for (node = params; node; node = jack_slist_next (node)) {
         param = (const jack_driver_param_t *) node->data;
@@ -875,6 +881,10 @@ SERVER_EXPORT Jack::JackDriverClientInterface* driver_initialize(Jack::JackLocke
             case 'X':
                 midi_driver = strdup(param->value.str);
                 break;
+
+            case 't':
+                hw_timestamping = param->value.i;
+                break;
         }
     }
 
@@ -889,7 +899,7 @@ SERVER_EXPORT Jack::JackDriverClientInterface* driver_initialize(Jack::JackLocke
     // Special open for ALSA driver...
     if (g_alsa_driver->Open(frames_per_interrupt, user_nperiods, srate, hw_monitoring, hw_metering, capture, playback, dither, soft_mode, monitor,
                           user_capture_nchnls, user_playback_nchnls, shorts_first, capture_pcm_name, playback_pcm_name,
-                          systemic_input_latency, systemic_output_latency, midi_driver) == 0) {
+                          systemic_input_latency, systemic_output_latency, midi_driver, hw_timestamping) == 0) {
         return threaded_driver;
     } else {
         delete threaded_driver; // Delete the decorated driver

linux/alsa/JackAlsaDriver.h

@@ -67,7 +67,8 @@ class JackAlsaDriver : public JackAudioDriver
                  const char* playback_driver_name,
                  jack_nframes_t capture_latency,
                  jack_nframes_t playback_latency,
-                 const char* midi_driver_name);
+                 const char* midi_driver_name,
+                 int hw_timestamping);
 
         int Close();
         int Attach();

linux/alsa/alsa_driver.c

@@ -589,6 +589,21 @@ alsa_driver_configure_stream (alsa_driver_t *driver, char *device_name,
 		return -1;
 	}
 
+	if (driver->hw_timestamping) {
+		err = snd_pcm_sw_params_set_tstamp_mode(handle, sw_params,
+							SND_PCM_TSTAMP_ENABLE);
+		if (err < 0) {
+			jack_info("Could not enable ALSA time stamp mode for %s (err %d)",
+				  stream_name, err);
+		}
+		err = snd_pcm_sw_params_set_tstamp_type(handle, sw_params,
+							SND_PCM_TSTAMP_TYPE_MONOTONIC);
+		if (err < 0) {
+			jack_info("Could not use monotonic ALSA time stamps for %s (err %d)",
+				  stream_name, err);
+		}
+	}
+
 	if ((err = snd_pcm_sw_params (handle, sw_params)) < 0) {
 		jack_error ("ALSA: cannot set software parameters for %s\n",
 			    stream_name);
@@ -1942,7 +1957,8 @@ alsa_driver_new (char *name, char *playback_alsa_device,
 		 int shorts_first,
 		 jack_nframes_t capture_latency,
 		 jack_nframes_t playback_latency,
-		 alsa_midi_t *midi_driver
+		 alsa_midi_t *midi_driver,
+		 int hw_timestamping
 		 )
 {
 	int err;
@@ -2028,6 +2044,7 @@ alsa_driver_new (char *name, char *playback_alsa_device,
 	driver->alsa_name_capture = strdup (capture_alsa_device);
 
 	driver->midi = midi_driver;
+	driver->hw_timestamping = hw_timestamping;
 	driver->xrun_recovery = 0;
 
 	if (alsa_driver_check_card_type (driver)) {

linux/alsa/alsa_driver.h

@@ -124,6 +124,7 @@ typedef struct _alsa_driver {
     char has_hw_monitoring;
     char has_hw_metering;
     char quirk_bswap;
+    char hw_timestamping;
 
     ReadCopyFunction read_via_copy;
     WriteCopyFunction write_via_copy;
@@ -248,7 +249,8 @@ alsa_driver_new (char *name, char *playback_alsa_device,
 		 int shorts_first,
 		 jack_nframes_t capture_latency,
 		 jack_nframes_t playback_latency,
-		 alsa_midi_t *midi_driver
+		 alsa_midi_t *midi_driver,
+		 int hw_timestamping
 		 );
 void
 alsa_driver_delete (alsa_driver_t *driver);