Add snd_pcm_parse_control_id()

Added a new function snd_pcm_parse_control_id() for the user controls.
This can be used in external plugins, too.

include/pcm_external.h

@@ -1,8 +1,42 @@
+/**
+ * \file include/pcm_external.h
+ * \brief External PCM plugin SDK
+ * \author Takashi Iwai <tiwai@suse.de>
+ * \date 2005
+ *
+ * Extern PCM plugin SDK.
+ */
+
+/*
+ *   This library is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU Lesser General Public License as
+ *   published by the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
+ *
+ *   You should have received a copy of the GNU Lesser General Public
+ *   License along with this library; if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ *
+ */
 #ifndef __ALSA_PCM_EXTERNAL_H
 #define __ALSA_PCM_EXTERNAL_H
 
 #include "pcm.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ *  \defgroup Plugin_SDK External PCM plugin SDK
+ *  \{
+ */
+
 #define SND_PCM_PLUGIN_ENTRY(name) _snd_pcm_##name##_open
 #define SND_PCM_PLUGIN_SYMBOL(name) SND_DLSYM_BUILD_VERSION(SND_PCM_PLUGIN_ENTRY(name), SND_PCM_DLSYM_VERSION);
 
@@ -14,4 +48,13 @@ int SND_PCM_PLUGIN_ENTRY(plugin) (snd_pcm_t **pcmp, const char *name,\
 #include "pcm_ioplug.h"
 #include "pcm_extplug.h"
 
+int snd_pcm_parse_control_id(snd_config_t *conf, snd_ctl_elem_id_t *ctl_id, int *cardp,
+			     int *cchannelsp, int *hwctlp);
+
+/** \} */
+
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* __ALSA_PCM_EXTERNAL_H */