axfer: add options for software parameters of PCM substream

In ALSA PCM interface, some parameters are used to configure runtime of
PCM substream independently of actual hardware. These parameters are
mainly used to decide the detailed timing to start/stop PCM substream and
release I/O blocking state of application. These parameters are
represented and delivered by a structure.

In alsa-lib PCM API, the structure is hidden from userspace applications.
The applications can set/get actual parameters by helper functions.

In aplay, three of the parameters are configurable. This commit adds
support for them. When no options are given, default values are used.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

axfer/xfer-libasound.c

@@ -17,7 +17,7 @@ enum no_short_opts {
 	OPT_TEST_NOWAIT,
 };
 
-#define S_OPTS	"D:NMF:B:"
+#define S_OPTS	"D:NMF:B:A:R:T:"
 static const struct option l_opts[] = {
 	{"device",		1, 0, 'D'},
 	{"nonblock",		0, 0, 'N'},
@@ -26,6 +26,9 @@ static const struct option l_opts[] = {
 	{"buffer-time",		1, 0, 'B'},
 	{"period-size",		1, 0, OPT_PERIOD_SIZE},
 	{"buffer-size",		1, 0, OPT_BUFFER_SIZE},
+	{"avail-min",		1, 0, 'A'},
+	{"start-delay",		1, 0, 'R'},
+	{"stop-delay",		1, 0, 'T'},
 	// For debugging.
 	{"fatal-errors",	0, 0, OPT_FATAL_ERRORS},
 	{"test-nowait",		0, 0, OPT_TEST_NOWAIT},
@@ -68,6 +71,12 @@ static int xfer_libasound_parse_opt(struct xfer_context *xfer, int key,
 		state->frames_per_period = arg_parse_decimal_num(optarg, &err);
 	else if (key == OPT_BUFFER_SIZE)
 		state->frames_per_buffer = arg_parse_decimal_num(optarg, &err);
+	else if (key == 'A')
+		state->msec_for_avail_min = arg_parse_decimal_num(optarg, &err);
+	else if (key == 'R')
+		state->msec_for_start_threshold = arg_parse_decimal_num(optarg, &err);
+	else if (key == 'T')
+		state->msec_for_stop_threshold = arg_parse_decimal_num(optarg, &err);
 	else if (key == OPT_FATAL_ERRORS)
 		state->finish_at_xrun = true;
 	else if (key == OPT_TEST_NOWAIT)
@@ -377,8 +386,76 @@ static int retrieve_actual_hw_params(snd_pcm_hw_params_t *hw_params,
 
 static int configure_sw_params(struct libasound_state *state,
 			       unsigned int frames_per_second,
-			       unsigned int frames_per_buffer)
+			       unsigned int frames_per_buffer,
+			       unsigned int msec_for_avail_min,
+			       unsigned int msec_for_start_threshold,
+			       unsigned int msec_for_stop_threshold)
 {
+	snd_pcm_uframes_t frame_count;
+	int err;
+
+	if (msec_for_avail_min > 0) {
+		frame_count = msec_for_avail_min * frames_per_second / 1000000;
+		if (frame_count == 0 || frame_count > frames_per_buffer) {
+			logging(state,
+				"The msec for 'avail_min' is too %s: %u "
+				"msec (%lu frames at %u).\n",
+				frame_count == 0 ? "small" : "large",
+				msec_for_avail_min, frame_count,
+				frames_per_second);
+			return -EINVAL;
+		}
+		err = snd_pcm_sw_params_set_avail_min(state->handle,
+						state->sw_params, frame_count);
+		if (err < 0) {
+			logging(state,
+				"Fail to configure 'avail-min'.\n");
+			return -EINVAL;
+		}
+	}
+
+	if (msec_for_start_threshold > 0) {
+		frame_count = msec_for_start_threshold * frames_per_second /
+			      1000000;
+		if (frame_count == 0 || frame_count > frames_per_buffer) {
+			logging(state,
+				"The msec for 'start-delay' is too %s: %u "
+				"msec (%lu frames at %u).\n",
+				frame_count == 0 ? "small" : "large",
+				msec_for_start_threshold, frame_count,
+				frames_per_second);
+			return -EINVAL;
+		}
+		err = snd_pcm_sw_params_set_start_threshold(state->handle,
+						state->sw_params, frame_count);
+		if (err < 0) {
+			logging(state,
+				"Fail to configure 'start-delay'.\n");
+			return -EINVAL;
+		}
+	}
+
+	if (msec_for_stop_threshold > 0) {
+		frame_count = msec_for_stop_threshold * frames_per_second /
+			      1000000;
+		if (frame_count == 0 || frame_count > frames_per_buffer) {
+			logging(state,
+				"The msec for 'stop-delay' is too %s: %u "
+				"msec (%lu frames at %u).\n",
+				frame_count == 0 ? "small" : "large",
+				msec_for_stop_threshold, frame_count,
+				frames_per_second);
+			return -EINVAL;
+		}
+		err = snd_pcm_sw_params_set_stop_threshold(state->handle,
+						state->sw_params, frame_count);
+		if (err < 0) {
+			logging(state,
+				"Fail to configure 'stop-delay'.\n");
+			return -EINVAL;
+		}
+	}
+
 	return snd_pcm_sw_params(state->handle, state->sw_params);
 }
 
@@ -444,7 +521,10 @@ static int xfer_libasound_pre_process(struct xfer_context *xfer,
 		return err;
 
 	err = configure_sw_params(state, *frames_per_second,
-				  *frames_per_buffer);
+				  *frames_per_buffer,
+				  state->msec_for_avail_min,
+				  state->msec_for_start_threshold,
+				  state->msec_for_stop_threshold);
 	if (err < 0) {
 		logging(state, "Current software parameters:\n");
 		snd_pcm_sw_params_dump(state->sw_params, state->log);

axfer/xfer-libasound.h

@@ -35,6 +35,10 @@ struct libasound_state {
 	unsigned int frames_per_period;
 	unsigned int frames_per_buffer;
 
+	unsigned int msec_for_avail_min;
+	unsigned int msec_for_start_threshold;
+	unsigned int msec_for_stop_threshold;
+
 	bool finish_at_xrun:1;
 	bool nonblock:1;
 	bool mmap:1;