module/alsa: monitors volume and muted state of selected card/mixer

modules/alsa.c

@@ -0,0 +1,148 @@
+#include "alsa.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <alsa/asoundlib.h>
+
+#define LOG_MODULE "alsa"
+#define LOG_ENABLE_DBG 1
+#include "../log.h"
+#include "../bar.h"
+
+struct private {
+    char *card;
+    char *mixer;
+    struct particle *label;
+
+    long vol_min;
+    long vol_max;
+    long vol_cur;
+    bool muted;
+};
+
+static void
+destroy(struct module *mod)
+{
+    struct private *m = mod->private;
+    m->label->destroy(m->label);
+    free(m->card);
+    free(m->mixer);
+    free(m);
+    module_default_destroy(mod);
+}
+
+static struct exposable *
+content(struct module *mod)
+{
+    struct private *m = mod->private;
+
+    mtx_lock(&mod->lock);
+    struct tag_set tags = {
+        .tags = (struct tag *[]){
+            tag_new_int_range(mod, "volume", m->vol_cur, m->vol_min, m->vol_max),
+            tag_new_bool(mod, "muted", m->muted),
+        },
+        .count = 2,
+    };
+    mtx_unlock(&mod->lock);
+
+    struct exposable *exposable = m->label->instantiate(m->label, &tags);
+
+    tag_set_destroy(&tags);
+    return exposable;
+}
+
+static void
+update_state(struct module *mod, snd_mixer_elem_t *elem)
+{
+    struct private *m = mod->private;
+
+    long cur, min, max;
+    snd_mixer_selem_get_playback_volume(elem, SND_MIXER_SCHN_MONO, &cur);
+    snd_mixer_selem_get_playback_volume_range(elem, &min, &max);
+
+    int unmuted;
+    snd_mixer_selem_get_playback_switch(elem, SND_MIXER_SCHN_MONO, &unmuted);
+
+    LOG_DBG("muted=%d, cur=%ld, min=%ld, max=%ld", !unmuted, cur, min, max);
+
+    mtx_lock(&mod->lock);
+    m->vol_min = min;
+    m->vol_max = max;
+    m->vol_cur = cur;
+    m->muted = !unmuted;
+    mtx_unlock(&mod->lock);
+
+    mod->bar->refresh(mod->bar);
+}
+
+static int
+run(struct module_run_context *ctx)
+{
+    struct module *mod = ctx->module;
+    struct private *m = mod->private;
+
+    module_signal_ready(ctx);
+
+    snd_mixer_t *handle;
+    snd_mixer_open(&handle, 0);
+    snd_mixer_attach(handle, m->card);
+    snd_mixer_selem_register(handle, NULL, NULL);
+    snd_mixer_load(handle);
+
+    snd_mixer_selem_id_t *sid;
+    snd_mixer_selem_id_alloca(&sid);
+    snd_mixer_selem_id_set_index(sid, 0);
+    snd_mixer_selem_id_set_name(sid, m->mixer);
+    snd_mixer_elem_t* elem = snd_mixer_find_selem(handle, sid);
+
+    /* Initial state */
+    update_state(mod, elem);
+
+    while (true) {
+        int fd_count = snd_mixer_poll_descriptors_count(handle);
+        assert(fd_count >= 1);
+
+        struct pollfd fds[1 + fd_count];
+
+        fds[0] = (struct pollfd){.fd = ctx->abort_fd, .events = POLLIN};
+        snd_mixer_poll_descriptors(handle, &fds[1], fd_count);
+
+        poll(fds, fd_count + 1, -1);
+
+        if (fds[0].revents & POLLIN)
+            break;
+
+        if (fds[1].revents & POLLHUP) {
+            /* Don't know if this can happen */
+            LOG_ERR("disconnected from alsa");
+            break;
+        }
+
+        snd_mixer_handle_events(handle);
+        update_state(mod, elem);
+    }
+
+    snd_mixer_close(handle);
+    snd_config_update_free_global();
+    return 0;
+}
+
+struct module *
+module_alsa(const char *card, const char *mixer, struct particle *label)
+{
+    struct private *priv = malloc(sizeof(*priv));
+    priv->label = label;
+    priv->card = strdup(card);
+    priv->mixer = strdup(mixer);
+    priv->vol_cur = priv->vol_min = priv->vol_max = 0;
+    priv->muted = true;
+
+    struct module *mod = module_common_new();
+    mod->private = priv;
+    mod->run = &run;
+    mod->destroy = &destroy;
+    mod->content = &content;
+    return mod;
+}