tinyalsa: add mixer_consume_event
mixer_consume_event consumes subscribed events from the mixer
in order to allow monitoring of mixer control value changed.
diff --git a/src/mixer.c b/src/mixer.c
index 1c9e63b..c8c6c2a 100644
--- a/src/mixer.c
+++ b/src/mixer.c
@@ -535,6 +535,27 @@
}
}
+/** Consume a mixer event.
+ * If mixer_subscribe_events has been called,
+ * mixer_wait_event will identify when a control value has changed.
+ * This function will clear a single event from the mixer so that
+ * further events can be alerted.
+ *
+ * @param mixer A mixer handle.
+ * @returns 0 on success. -errno on failure.
+ * @ingroup libtinyalsa-mixer
+ */
+int mixer_consume_event(struct mixer *mixer) {
+ struct snd_ctl_event ev;
+ ssize_t count = read(mixer->fd, &ev, sizeof(ev));
+ // Exporting the actual event would require exposing snd_ctl_event
+ // via the header file, and all associated structs.
+ // The events generally tell you exactly which value changed,
+ // but reading values you're interested isn't hard and simplifies
+ // the interface greatly.
+ return (count >= 0) ? 0 : -errno;
+}
+
static unsigned int mixer_grp_get_count(struct mixer_ctl_group *grp)
{
if (!grp)