- added asym plugin.

src/pcm/pcm_asym.c

@@ -0,0 +1,118 @@
+/**
+ * \file pcm/pcm_asym.c
+ * \ingroup PCM_Plugins
+ * \brief PCM Asymmetrical Plugin Interface
+ * \author Takashi Iwai <tiwai@suse.de>
+ * \date 2003
+ */
+
+#include "pcm_local.h"
+
+#ifndef PIC
+/* entry for static linking */
+const char *_snd_module_pcm_asym = "";
+#endif
+
+/*! \page pcm_plugins
+
+\section pcm_plugins_asym Plugin: asym
+
+This plugin is a combination of playback and capture PCM streams.
+Slave PCMs can be defined asymmetrically for both directions.
+
+\code
+pcm.name {
+        type asym               # Asym PCM
+        playback STR            # Playback slave name
+        # or
+        playback {              # Playback slave definition
+                pcm STR         # Slave PCM name
+                # or
+                pcm { }         # Slave PCM definition
+        }
+        capture STR             # Capture slave name
+        # or
+        capture {               # Capture slave definition
+                pcm STR         # Slave PCM name
+                # or
+                pcm { }         # Slave PCM definition
+        }
+}
+\endcode
+
+For example, you can combine a dmix plugin and a dsnoop plugin as
+as a single PCM for playback and capture directions, respectively.
+\code
+pcm.duplex {
+	type asym
+	playback.pcm "dmix"
+	capture.pcm "dsnoop"
+}
+\endcode
+
+By defining only a single direction, the resultant PCM becomes
+half-duplex.
+
+\subsection pcm_plugins_asym_funcref Function reference
+
+<UL>
+  <LI>_snd_pcm_asym_open()
+</UL>
+
+*/
+
+/**
+ * \brief Creates a new asym stream PCM
+ * \param pcmp Returns created PCM handle
+ * \param name Name of PCM
+ * \param root Root configuration node
+ * \param conf Configuration node with copy PCM description
+ * \param stream Stream type
+ * \param mode Stream mode
+ * \retval zero on success otherwise a negative error code
+ * \warning Using of this function might be dangerous in the sense
+ *          of compatibility reasons. The prototype might be freely
+ *          changed in future.
+ */
+int _snd_pcm_asym_open(snd_pcm_t **pcmp, const char *name ATTRIBUTE_UNUSED,
+			 snd_config_t *root, snd_config_t *conf,
+			 snd_pcm_stream_t stream, int mode)
+{
+	snd_config_iterator_t i, next;
+	int err;
+	snd_config_t *slave = NULL, *sconf;
+	snd_config_for_each(i, next, conf) {
+		snd_config_t *n = snd_config_iterator_entry(i);
+		const char *id;
+		if (snd_config_get_id(n, &id) < 0)
+			continue;
+		if (snd_pcm_conf_generic_id(id))
+			continue;
+		if (strcmp(id, "playback") == 0) {
+			if (stream == SND_PCM_STREAM_PLAYBACK)
+				slave = n;
+			continue;
+		}
+		if (strcmp(id, "capture") == 0) {
+			if (stream == SND_PCM_STREAM_CAPTURE)
+				slave = n;
+			continue;
+		}
+		SNDERR("Unknown field %s", id);
+		return -EINVAL;
+	}
+	if (! slave) {
+		SNDERR("%s slave is not defined",
+		       stream == SND_PCM_STREAM_PLAYBACK ? "playback" : "capture");
+		return -EINVAL;
+	}
+	err = snd_pcm_slave_conf(root, slave, &sconf, 0);
+	if (err < 0)
+		return err;
+	err = snd_pcm_open_slave(pcmp, root, sconf, stream, mode);
+	snd_config_delete(sconf);
+	return err;
+}
+#ifndef DOC_HIDDEN
+SND_DLSYM_BUILD_VERSION(_snd_pcm_asym_open, SND_PCM_DLSYM_VERSION);
+#endif