add API to query ALSA supported parameters

libs/ardouralsautil/ardouralsautil/deviceinfo.h

@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2015 Robin Gareus <robin@gareus.org>
+ * Copyright (C) 2013 Paul Davis
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef __libardouralsautil_deviceinfo_h__
+#define __libardouralsautil_deviceinfo_h__
+
+namespace ARDOUR {
+
+	struct ALSADeviceInfo {
+		unsigned int max_channels;
+		unsigned int min_rate, max_rate;
+		unsigned long min_size, max_size;
+		bool valid;
+	};
+
+	int get_alsa_device_parameters (const char* device_name, const bool play, ALSADeviceInfo *nfo);
+}
+#endif

libs/ardouralsautil/deviceparams.cc

@@ -0,0 +1,88 @@
+/*
+ * Copyright (C) 2015 Robin Gareus <robin@gareus.org>
+ * Copyright (C) 2013 Paul Davis
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <alsa/asoundlib.h>
+#include "pbd/convert.h"
+#include "ardouralsautil/deviceinfo.h"
+
+using namespace std;
+
+int
+ARDOUR::get_alsa_device_parameters (const char* device_name, const bool play, ALSADeviceInfo *nfo)
+{
+	snd_pcm_t *pcm;
+	snd_pcm_hw_params_t *hw_params;
+	std::string errmsg;
+	int err;
+
+	nfo->valid = false;
+
+	err = snd_pcm_open (&pcm, device_name,
+			play ? SND_PCM_STREAM_PLAYBACK : SND_PCM_STREAM_CAPTURE,
+			SND_PCM_NONBLOCK);
+
+	if (err < 0) {
+		fprintf (stderr, "ALSA: Cannot open device '%s': %s\n", device_name, snd_strerror (err));
+		return 1;
+	}
+
+	snd_pcm_hw_params_alloca (&hw_params);
+	err = snd_pcm_hw_params_any (pcm, hw_params);
+	if (err < 0) {
+		errmsg = "Cannot get hardware parameters";
+		goto error_out;
+	}
+
+	err = snd_pcm_hw_params_get_channels_max (hw_params, &nfo->max_channels);
+	if (err < 0) {
+		errmsg = "Cannot get maximum channels count";
+		goto error_out;
+	}
+
+	err = snd_pcm_hw_params_get_rate_min (hw_params, &nfo->min_rate, NULL);
+	if (err < 0) {
+		errmsg = "Cannot get minimum rate";
+		goto error_out;
+	}
+	err = snd_pcm_hw_params_get_rate_max (hw_params, &nfo->max_rate, NULL);
+	if (err < 0) {
+		errmsg = "Cannot get maximum rate";
+		goto error_out;
+	}
+
+	err = snd_pcm_hw_params_get_buffer_size_min (hw_params, &nfo->min_size);
+	if (err < 0) {
+		errmsg = "Cannot get minimum buffer size";
+		goto error_out;
+	}
+	err = snd_pcm_hw_params_get_buffer_size_max (hw_params, &nfo->max_size);
+	if (err < 0) {
+		errmsg = "Cannot get maximum buffer size";
+		goto error_out;
+	}
+	snd_pcm_close (pcm);
+	nfo->valid = true;
+	return 0;
+
+error_out:
+	fprintf (stderr, "ALSA: %s: %s\n", errmsg.c_str(), snd_strerror (err));
+	snd_pcm_close (pcm);
+	return 1;
+
+}

libs/ardouralsautil/wscript

@@ -26,7 +26,8 @@ def build(bld):
         if bld.is_defined('HAVE_ALSA'):
             obj = bld(features = 'cxx cxxshlib')
             obj.source = [
-                'devicelist.cc'
+                'devicelist.cc',
+                'deviceparams.cc'
             ]
             obj.export_includes = ['.']
             obj.includes = ['.']