lib/alsa/HwSetup: return effective parameters

src/lib/alsa/HwSetup.cxx

@@ -176,11 +176,14 @@ SetupSampleFormat(snd_pcm_t *pcm, snd_pcm_hw_params_t *hwparams,
 	return err;
 }
 
-void
-SetupHw(snd_pcm_t *pcm, snd_pcm_hw_params_t *hwparams,
+HwResult
+SetupHw(snd_pcm_t *pcm,
 	unsigned buffer_time, unsigned period_time,
 	AudioFormat &audio_format, PcmExport::Params &params)
 {
+	snd_pcm_hw_params_t *hwparams;
+	snd_pcm_hw_params_alloca(&hwparams);
+
 	int err;
 	unsigned int period_time_ro = period_time;
 
@@ -285,6 +288,26 @@ SetupHw(snd_pcm_t *pcm, snd_pcm_hw_params_t *hwparams,
 	if (err < 0)
 		throw FormatRuntimeError("snd_pcm_hw_params() failed: %s",
 					 snd_strerror(-err));
+
+	HwResult result;
+
+	err = snd_pcm_hw_params_get_format(hwparams, &result.format);
+	if (err < 0)
+		throw FormatRuntimeError("snd_pcm_hw_params_get_format() failed: %s",
+					 snd_strerror(-err));
+
+	err = snd_pcm_hw_params_get_buffer_size(hwparams, &result.buffer_size);
+	if (err < 0)
+		throw FormatRuntimeError("snd_pcm_hw_params_get_buffer_size() failed: %s",
+					 snd_strerror(-err));
+
+	err = snd_pcm_hw_params_get_period_size(hwparams, &result.period_size,
+						nullptr);
+	if (err < 0)
+		throw FormatRuntimeError("snd_pcm_hw_params_get_period_size() failed: %s",
+					 snd_strerror(-err));
+
+	return result;
 }
 
 } // namespace Alsa

src/lib/alsa/HwSetup.hxx

@@ -29,6 +29,11 @@ struct AudioFormat;
 
 namespace Alsa {
 
+struct HwResult {
+	snd_pcm_format_t format;
+	snd_pcm_uframes_t buffer_size, period_size;
+};
+
 /**
  * Wrapper for snd_pcm_hw_params().
  *
@@ -38,8 +43,8 @@ namespace Alsa {
  * by this function
  * @param params to be modified by this function
  */
-void
-SetupHw(snd_pcm_t *pcm, snd_pcm_hw_params_t *hwparams,
+HwResult
+SetupHw(snd_pcm_t *pcm,
 	unsigned buffer_time, unsigned period_time,
 	AudioFormat &audio_format, PcmExport::Params &params);
 

src/output/plugins/AlsaOutputPlugin.cxx

@@ -392,38 +392,22 @@ inline void
 AlsaOutput::Setup(AudioFormat &audio_format,
 		  PcmExport::Params &params)
 {
-	snd_pcm_hw_params_t *hwparams;
-	snd_pcm_hw_params_alloca(&hwparams);
+	const auto hw_result = Alsa::SetupHw(pcm,
+					     buffer_time, period_time,
+					     audio_format, params);
 
-	Alsa::SetupHw(pcm, hwparams,
-		      buffer_time, period_time,
-		      audio_format, params);
-
-	snd_pcm_format_t format;
-	if (snd_pcm_hw_params_get_format(hwparams, &format) == 0)
-		FormatDebug(alsa_output_domain,
-			    "format=%s (%s)", snd_pcm_format_name(format),
-			    snd_pcm_format_description(format));
-
-	snd_pcm_uframes_t alsa_buffer_size;
-	int err = snd_pcm_hw_params_get_buffer_size(hwparams, &alsa_buffer_size);
-	if (err < 0)
-		throw FormatRuntimeError("snd_pcm_hw_params_get_buffer_size() failed: %s",
-					 snd_strerror(-err));
-
-	snd_pcm_uframes_t alsa_period_size;
-	err = snd_pcm_hw_params_get_period_size(hwparams, &alsa_period_size,
-						nullptr);
-	if (err < 0)
-		throw FormatRuntimeError("snd_pcm_hw_params_get_period_size() failed: %s",
-					 snd_strerror(-err));
-
-	AlsaSetupSw(pcm, alsa_buffer_size - alsa_period_size,
-		    alsa_period_size);
+	FormatDebug(alsa_output_domain, "format=%s (%s)",
+		    snd_pcm_format_name(hw_result.format),
+		    snd_pcm_format_description(hw_result.format));
 
 	FormatDebug(alsa_output_domain, "buffer_size=%u period_size=%u",
-		    (unsigned)alsa_buffer_size, (unsigned)alsa_period_size);
+		    (unsigned)hw_result.buffer_size,
+		    (unsigned)hw_result.period_size);
+
+	AlsaSetupSw(pcm, hw_result.buffer_size - hw_result.period_size,
+		    hw_result.period_size);
 
+	auto alsa_period_size = hw_result.period_size;
 	if (alsa_period_size == 0)
 		/* this works around a SIGFPE bug that occurred when
 		   an ALSA driver indicated period_size==0; this
@@ -435,7 +419,7 @@ AlsaOutput::Setup(AudioFormat &audio_format,
 	period_frames = alsa_period_size;
 
 	silence = new uint8_t[snd_pcm_frames_to_bytes(pcm, alsa_period_size)];
-	snd_pcm_format_set_silence(format, silence,
+	snd_pcm_format_set_silence(hw_result.format, silence,
 				   alsa_period_size * audio_format.channels);
 
 }