Pulseaudio alsa configure hook

The attached patch extends the alsa pulse plugin set with a alsa
configuration hook. Allowing one to specify some configuration parameters
that only come into effect when pulseaudio is running.

For example a configution file like:

    @hooks [ {
       func on_pulse_is_running
         pcm.!default { type pulse }
         ctl.!default { type pulse }
       }
   ]

will redirect the default alsa pcm and ctl to pulse iff pulse is running.
(Assuming you defined the hook function correctly ofcourse)

This is usefull for distributions that don't want to force their users to
switch completely to pulseaudio, but have things a bit more dynamic :)

The solutions isn't optimal though. It will mean that every program loading
accessing alsa will try to make an (extra) connection to pulse to decide what
to do. But i think it's the best we can do for now (or at least that i can do
with my minimal knowledge of alsa).

A nicer solution would be a way to always specify the pulse plugin as default
and have a sort of fallback for when that fails.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

2 files changed, 93 insertions, 0 deletions

diff --git a/pulse/Makefile.am b/pulse/Makefile.am
index 2b18ab6..525a21c 100644
--- a/pulse/Makefile.am
+++ b/pulse/Makefile.am
@@ -1,8 +1,10 @@
 asound_module_pcm_LTLIBRARIES = libasound_module_pcm_pulse.la
 asound_module_ctl_LTLIBRARIES = libasound_module_ctl_pulse.la
+asound_module_conf_LTLIBRARIES = libasound_module_conf_pulse.la
 
 asound_module_pcmdir = @ALSA_PLUGIN_DIR@
 asound_module_ctldir = @ALSA_PLUGIN_DIR@
+asound_module_confdir = @ALSA_PLUGIN_DIR@
 
 AM_CFLAGS = -Wall -g @ALSA_CFLAGS@ $(PTHREAD_CFLAGS) $(pulseaudio_CFLAGS) -D_GNU_SOURCE
 AM_LDFLAGS = -module -avoid-version -export-dynamic -no-undefined
@@ -12,3 +14,6 @@ libasound_module_pcm_pulse_la_LIBADD = @ALSA_LIBS@ $(PTHREAD_LIBS) $(pulseaudio_
 
 libasound_module_ctl_pulse_la_SOURCES = ctl_pulse.c pulse.c pulse.h
 libasound_module_ctl_pulse_la_LIBADD = @ALSA_LIBS@ $(PTHREAD_LIBS) $(pulseaudio_LIBS)
+
+libasound_module_conf_pulse_la_SOURCES = conf_pulse.c
+libasound_module_conf_pulse_la_LIBADD = @ALSA_LIBS@ $(PTHREAD_LIBS) $(pulseaudio_LIBS)
diff --git a/pulse/conf_pulse.c b/pulse/conf_pulse.c
new file mode 100644
index 0000000..78cf042
--- /dev/null
+++ b/pulse/conf_pulse.c
@@ -0,0 +1,88 @@
+/*
+ * ALSA configuration function extensions for pulse
+ *
+ * Copyright (c) 2008 by Sjoerd Simons <sjoerd@luon.net>
+ *
+ * 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
+ *
+ */
+
+#include <stdio.h>
+
+#include <alsa/asoundlib.h>
+#include <pulse/pulseaudio.h>
+
+
+int
+conf_pulse_hook_on_is_running (snd_config_t *root, snd_config_t *config,
+    snd_config_t **dst, snd_config_t *private_data) {
+  snd_config_t *n = NULL;
+  pa_mainloop *loop = NULL;
+  pa_context *context = NULL;
+  int ret = 0, err, state;
+
+
+  /* Defined if we're called inside the pulsedaemon itself */
+  if (getenv("PULSE_INTERNAL") != NULL)
+    goto out;
+
+  loop = pa_mainloop_new();
+  if (loop == NULL)
+    goto out;
+
+  context = pa_context_new(pa_mainloop_get_api(loop), "Alsa hook");
+  if (context == NULL)
+    goto out;
+
+  err = pa_context_connect (context, NULL, 0, NULL);
+  if (err < 0)
+    goto out;
+
+  do {
+    err = pa_mainloop_prepare (loop, -1);
+    if (err < 0)
+       goto out;
+
+    err = pa_mainloop_poll (loop);
+    if (err < 0)
+      goto out;
+
+    err = pa_mainloop_dispatch (loop);
+    if (err < 0)
+      goto out;
+
+    state = pa_context_get_state(context);
+  } while (state < PA_CONTEXT_READY);
+
+  if (state != PA_CONTEXT_READY)
+    goto out;
+
+  ret = snd_config_expand(config, root, NULL, private_data, &n);
+
+out:
+  if (context != NULL)
+    pa_context_unref(context);
+
+  if (loop != NULL)
+    pa_mainloop_free(loop);
+
+  *dst = n;
+
+  return ret;
+}
+
+SND_DLSYM_BUILD_VERSION(conf_pulse_hook_on_is_running,
+  SND_CONFIG_DLSYM_VERSION_HOOK);