[alsa-devel] [RFCv3][PATCH 28/39] axfer: add options for software parameters of PCM substream

[Takashi Sakamoto]

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 at sakamocchi.jp>
---
 axfer/options.c        | 11 +++++++-
 axfer/options.h        |  4 +++
 axfer/xfer-libasound.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 86 insertions(+), 3 deletions(-)

diff --git a/axfer/options.c b/axfer/options.c
index 325bc16b..a22223a0 100644
--- a/axfer/options.c
+++ b/axfer/options.c
@@ -322,7 +322,7 @@ void context_options_calculate_duration(struct context_options *opts,
 int context_options_init(struct context_options *opts, int argc,
 			 char *const *argv, snd_pcm_stream_t direction)
 {
-	static const char *s_opts = "hvqd:s:t:ID:f:c:r:NMF:B:";
+	static const char *s_opts = "hvqd:s:t:ID:f:c:r:NMF:B:A:R:T:";
 	static const struct option l_opts[] = {
 		/* For generic purposes. */
 		{"help",		0, 0, 'h'},
@@ -345,6 +345,9 @@ int context_options_init(struct context_options *opts, int argc,
 		{"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. */
 		{"dump-hw-params",	0, 0, OPT_DUMP_HW_PARAMS},
 		{"fatal-errors",	0, 0, OPT_FATAL_ERRORS},
@@ -400,6 +403,12 @@ int context_options_init(struct context_options *opts, int argc,
 			opts->frames_per_period = parse_l(optarg, &err);
 		else if (c == OPT_BUFFER_SIZE)
 			opts->frames_per_buffer = parse_l(optarg, &err);
+		else if (c == 'A')
+			opts->msec_for_avail_min = parse_l(optarg, &err);
+		else if (c == 'R')
+			opts->msec_for_start_threshold = parse_l(optarg, &err);
+		else if (c == 'T')
+			opts->msec_for_stop_threshold = parse_l(optarg, &err);
 		else if (c == OPT_DUMP_HW_PARAMS)
 			opts->dump_hw_params = true;
 		else if (c == OPT_FATAL_ERRORS)
diff --git a/axfer/options.h b/axfer/options.h
index f4ac6c64..63b36364 100644
--- a/axfer/options.h
+++ b/axfer/options.h
@@ -41,6 +41,10 @@ struct context_options {
 	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;
+
 	/* For debugging. */
 	bool dump_hw_params;
 	bool finish_at_xrun;
diff --git a/axfer/xfer-libasound.c b/axfer/xfer-libasound.c
index 1911c160..533c9492 100644
--- a/axfer/xfer-libasound.c
+++ b/axfer/xfer-libasound.c
@@ -337,8 +337,76 @@ 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);
 }
 
@@ -403,7 +471,9 @@ 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, opts->msec_for_avail_min,
+				  opts->msec_for_start_threshold,
+				  opts->msec_for_stop_threshold);
 	if (err < 0) {
 		logging(state, _("Current software parameters:\n"));
 		snd_pcm_sw_params_dump(state->sw_params, state->log);
-- 
2.11.0