From e1eccedf0b08ae0ee49ae71efcbdcefc7107682b Mon Sep 17 00:00:00 2001
From: Anton Khirnov <anton@khirnov.net>
Date: Tue, 31 May 2016 15:56:22 +0200
Subject: Initial commit.

---
 Makefile    |  21 +++++++++
 mixnotify.c | 141 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 162 insertions(+)
 create mode 100644 Makefile
 create mode 100644 mixnotify.c

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..91e2718
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,21 @@
+CFLAGS = -std=c99 -D_XOPEN_SOURCE=700 -fPIC -g
+LDFLAGS = -lasound
+
+TARGET = mixnotify
+
+OBJS = mixnotify.o
+
+all: $(TARGET)
+
+$(TARGET): $(OBJS)
+	cc ${LDFLAGS} -o $@ $(OBJS)
+
+%.o: %.c
+	cc $(CFLAGS) -MMD -MF $(@:.o=.d) -MT $@ -c -o $@ $<
+
+clean:
+	-rm -f *.o *.d $(TARGET)
+
+-include $(OBJS:.o=.d)
+
+.PHONY: clean
diff --git a/mixnotify.c b/mixnotify.c
new file mode 100644
index 0000000..734ffc0
--- /dev/null
+++ b/mixnotify.c
@@ -0,0 +1,141 @@
+/*
+ * Copyright (C) 2016 Anton Khirnov <anton@khirnov.net>
+ *
+ * mixnotify 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 3 of the License, or
+ * (at your option) any later version.
+ *
+ * mixnotify 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 mixnotify.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <alsa/asoundlib.h>
+
+#include <stdio.h>
+#include <string.h>
+
+typedef struct MixerPrivate {
+    snd_mixer_elem_t *elem;
+} MixerPrivate;
+
+static int elem_callback(snd_mixer_elem_t *elem, unsigned int mask)
+{
+    MixerPrivate *s = snd_mixer_elem_get_callback_private(elem);
+    long val, min, max;
+    int ret;
+
+    if (!(mask & SND_CTL_EVENT_MASK_VALUE))
+        return 0;
+
+    ret = snd_mixer_selem_get_playback_volume(elem, SND_MIXER_SCHN_UNKNOWN, &val);
+    if (ret < 0) {
+        fprintf(stderr, "Error getting element volume: %d (%s)\n");
+        return ret;
+    }
+
+    ret = snd_mixer_selem_get_playback_volume_range(elem, &min, &max);
+    if (ret < 0) {
+        fprintf(stderr, "Error getting element volume range: %d (%s)\n",
+                ret, snd_strerror(ret));
+        return ret;
+    }
+
+    fprintf(stdout, "%ld %ld %ld\n", val, min, max);
+    fflush(stdout);
+
+    return 0;
+}
+
+int main(int argc, const char **argv)
+{
+    static const char  *ctl_name = "default";
+    static const char *elem_name = "Master";
+
+    MixerPrivate priv = { NULL };
+
+    snd_mixer_t *mixer = NULL;
+    snd_mixer_elem_t *elem;
+    int ret;
+
+    if (argc > 1)
+        ctl_name = argv[1];
+    if (argc > 2)
+        elem_name = argv[2];
+
+    fprintf(stderr, "Using CTL: %s\n", ctl_name);
+    fprintf(stderr, "Using mixer element: %s\n", elem_name);
+
+    ret = snd_mixer_open(&mixer, 0);
+    if (ret < 0) {
+        fprintf(stderr, "Error opening a new mixer: %d (%s)\n",
+                ret, snd_strerror(ret));
+        return -1;
+    }
+
+    ret = snd_mixer_attach(mixer, ctl_name);
+    if (ret < 0) {
+        fprintf(stderr, "Error attachng a HCTL '%s' to the mixer: %d (%s)\n",
+                ctl_name, ret, snd_strerror(ret));
+        ret = -1;
+        goto fail;
+    }
+
+    ret = snd_mixer_selem_register(mixer, NULL, NULL);
+    if (ret < 0) {
+        fprintf(stderr, "Error registering simple element class: %d (%s)\n",
+                ctl_name, ret, snd_strerror(ret));
+        ret = -1;
+        goto fail;
+    }
+
+    ret = snd_mixer_load(mixer);
+    if (ret < 0) {
+        fprintf(stderr, "Error loading mixer elements: %d (%s)\n",
+                ret, snd_strerror(ret));
+        ret = -1;
+        goto fail;
+    }
+
+    for (elem = snd_mixer_first_elem(mixer); elem; elem = snd_mixer_elem_next(elem)) {
+        snd_mixer_elem_type_t type = snd_mixer_elem_get_type(elem);
+
+        if (type == SND_MIXER_ELEM_SIMPLE &&
+            !strcmp(snd_mixer_selem_get_name(elem), elem_name))
+            break;
+    }
+    if (!elem) {
+        fprintf(stderr, "Mixer element '%s' not found\n", elem_name);
+        ret = -1;
+        goto fail;
+    }
+
+    snd_mixer_elem_set_callback_private(elem, &priv);
+    snd_mixer_elem_set_callback(elem, elem_callback);
+
+    while (!(ret = snd_mixer_wait(mixer, -1))) {
+        ret = snd_mixer_handle_events(mixer);
+        if (ret < 0) {
+            fprintf(stderr, "Error handling events: %d (%s)\n",
+                    ret, snd_strerror(ret));
+            ret = -1;
+            goto fail;
+        }
+    }
+    if (ret < 0) {
+        fprintf(stderr, "Error waiting for mixer events: %d (%s)\n",
+                ret, snd_strerror(ret));
+        ret = -1;
+        goto fail;
+    }
+
+fail:
+    snd_mixer_close(mixer);
+
+    return ret;
+}
-- 
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