Return meaningful error codes when ALSA backend fails to start

Unfortunately it seems that in zita-alsa-pcmi doesn't set state() correctly in
some cases. Setting an invalid SR doesn't display the correct error message,
first guess would be that set_hwpar is failing and state() is not
representative of the actual error.

diff --git a/libs/backends/alsa/alsa_audiobackend.cc b/libs/backends/alsa/alsa_audiobackend.cc
index 99b80f17d511d4e1ad5a3c885ade61f585c086d1..36ea6a5cc8bc23764b0c9107936b30b61b44b3f2 100644 (file)
--- a/libs/backends/alsa/alsa_audiobackend.cc
+++ b/libs/backends/alsa/alsa_audiobackend.cc
@@ -752,20 +752,48 @@ AlsaAudioBackend::_start (bool for_latency_measurement)
                        (duplex & 2) ? alsa_device.c_str() : NULL,
                        (duplex & 1) ? alsa_device.c_str() : NULL,
                        0, _samplerate, _samples_per_period, _periods_per_cycle, 0);
-       switch (_pcmi->state ()) {
-               case 0: /* OK */ break;
-               case -1: PBD::error << _("AlsaAudioBackend: failed to open device.") << endmsg; break;
-               case -2: PBD::error << _("AlsaAudioBackend: failed to allocate parameters.") << endmsg; break;
-               case -3: PBD::error << _("AlsaAudioBackend: cannot set requested sample rate.") << endmsg; break;
-               case -4: PBD::error << _("AlsaAudioBackend: cannot set requested period size.") << endmsg; break;
-               case -5: PBD::error << _("AlsaAudioBackend: cannot set requested number of periods.") << endmsg; break;
-               case -6: PBD::error << _("AlsaAudioBackend: unsupported sample format.") << endmsg; break;
-               default: PBD::error << _("AlsaAudioBackend: initialization failed.") << endmsg; break;
+
+       AudioBackend::ErrorCode error_code = NoError;
+       switch (_pcmi->state()) {
+       case 0: /* OK */
+               break;
+       case -1:
+               PBD::error << _("AlsaAudioBackend: failed to open device.") << endmsg;
+               error_code = AudioDeviceOpenError;
+               break;
+       case -2:
+               PBD::error << _("AlsaAudioBackend: failed to allocate parameters.") << endmsg;
+               error_code = AudioDeviceOpenError;
+               break;
+       case -3:
+               PBD::error << _("AlsaAudioBackend: cannot set requested sample rate.")
+                          << endmsg;
+               error_code = SampleRateNotSupportedError;
+               break;
+       case -4:
+               PBD::error << _("AlsaAudioBackend: cannot set requested period size.")
+                          << endmsg;
+               error_code = PeriodSizeNotSupportedError;
+               break;
+       case -5:
+               PBD::error << _("AlsaAudioBackend: cannot set requested number of periods.")
+                          << endmsg;
+               error_code = PeriodCountNotSupportedError;
+               break;
+       case -6:
+               PBD::error << _("AlsaAudioBackend: unsupported sample format.") << endmsg;
+               error_code = SampleFormatNotSupportedError;
+               break;
+       default:
+               PBD::error << _("AlsaAudioBackend: initialization failed.") << endmsg;
+               error_code = AudioDeviceOpenError;
+               break;
        }
+
        if (_pcmi->state ()) {
                delete _pcmi; _pcmi = 0;
                release_device();
-               return -1;
+               return error_code;
        }
 
 #ifndef NDEBUG