ALSA: core: Expose sound card online/offline state

Expose sound card online/offline state to procfs so userspace application
can poll and read sound card's state.

Change-Id: Ie605ad57f4ce5abf62a216e790407029658ac3c9
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>
Signed-off-by: Sudheer Papothi <spapothi@codeaurora.org>
Signed-off-by: Meng Wang <mwang@codeaurora.org>

include/sound/core.h

@@ -134,6 +134,9 @@ struct snd_card {
 	const struct attribute_group *dev_groups[4]; /* assigned sysfs attr */
 	bool registered;		/* card_dev is registered? */
 	wait_queue_head_t remove_sleep;
+	int offline;			/* if this sound card is offline */
+	unsigned long offline_change;
+	wait_queue_head_t offline_poll_wait;
 
 #ifdef CONFIG_PM
 	unsigned int power_state;	/* power state */
@@ -253,6 +256,8 @@ int snd_component_add(struct snd_card *card, const char *component);
 int snd_card_file_add(struct snd_card *card, struct file *file);
 int snd_card_file_remove(struct snd_card *card, struct file *file);
 #define snd_card_unref(card)	put_device(&(card)->card_dev)
+void snd_card_change_online_state(struct snd_card *card, int online);
+bool snd_card_is_online_state(struct snd_card *card);
 
 #define snd_card_set_dev(card, devptr) ((card)->dev = (devptr))
 

include/sound/soc.h

@@ -556,6 +556,8 @@ static inline void snd_soc_jack_free_gpios(struct snd_soc_jack *jack, int count,
 }
 #endif
 
+void snd_soc_card_change_online_state(struct snd_soc_card *soc_card,
+				      int online);
 #ifdef CONFIG_SND_SOC_AC97_BUS
 struct snd_ac97 *snd_soc_alloc_ac97_component(struct snd_soc_component *component);
 struct snd_ac97 *snd_soc_new_ac97_component(struct snd_soc_component *component,

sound/core/init.c

@@ -58,6 +58,8 @@ static char *slots[SNDRV_CARDS];
 module_param_array(slots, charp, NULL, 0444);
 MODULE_PARM_DESC(slots, "Module names assigned to the slots.");
 
+#define SND_CARD_STATE_MAX_LEN 16
+
 /* return non-zero if the given index is reserved for the given
  * module via slots option
  */
@@ -107,9 +109,39 @@ static void snd_card_id_read(struct snd_info_entry *entry,
 	snd_iprintf(buffer, "%s\n", entry->card->id);
 }
 
+static ssize_t snd_card_state_read(struct snd_info_entry *entry,
+			       void *file_private_data, struct file *file,
+			       char __user *buf, size_t count, loff_t pos)
+{
+	int len;
+	char buffer[SND_CARD_STATE_MAX_LEN];
+
+	/* make sure offline is updated prior to wake up */
+	rmb();
+	len = snprintf(buffer, sizeof(buffer), "%s\n",
+		       entry->card->offline ? "OFFLINE" : "ONLINE");
+	return simple_read_from_buffer(buf, count, &pos, buffer, len);
+}
+
+static unsigned int snd_card_state_poll(struct snd_info_entry *entry,
+					void *private_data, struct file *file,
+					poll_table *wait)
+{
+	poll_wait(file, &entry->card->offline_poll_wait, wait);
+	if (xchg(&entry->card->offline_change, 0))
+		return POLLIN | POLLPRI | POLLRDNORM;
+	else
+		return 0;
+}
+
+static struct snd_info_entry_ops snd_card_state_proc_ops = {
+	.read = snd_card_state_read,
+	.poll = snd_card_state_poll,
+};
+
 static int init_info_for_card(struct snd_card *card)
 {
-	struct snd_info_entry *entry;
+	struct snd_info_entry *entry, *entry_state;
 
 	entry = snd_info_create_card_entry(card, "id", card->proc_root);
 	if (!entry) {
@@ -119,6 +151,17 @@ static int init_info_for_card(struct snd_card *card)
 	entry->c.text.read = snd_card_id_read;
 	card->proc_id = entry;
 
+	entry_state = snd_info_create_card_entry(card, "state",
+						 card->proc_root);
+	if (!entry_state) {
+		dev_dbg(card->dev, "unable to create card entry state\n");
+		card->proc_id = NULL;
+		return -ENOMEM;
+	}
+	entry_state->size = SND_CARD_STATE_MAX_LEN;
+	entry_state->content = SNDRV_INFO_CONTENT_DATA;
+	entry_state->c.ops = &snd_card_state_proc_ops;
+
 	return snd_info_card_register(card);
 }
 #else /* !CONFIG_SND_PROC_FS */
@@ -257,6 +300,7 @@ int snd_card_new(struct device *parent, int idx, const char *xid,
 #endif
 	init_waitqueue_head(&card->remove_sleep);
 
+	init_waitqueue_head(&card->offline_poll_wait);
 	device_initialize(&card->card_dev);
 	card->card_dev.parent = parent;
 	card->card_dev.class = sound_class;
@@ -1000,6 +1044,35 @@ int snd_card_file_remove(struct snd_card *card, struct file *file)
 }
 EXPORT_SYMBOL(snd_card_file_remove);
 
+/**
+ * snd_card_change_online_state - mark card's online/offline state
+ * @card: Card to mark
+ * @online: whether online of offline
+ *
+ * Mutes the DAI DAC.
+ */
+void snd_card_change_online_state(struct snd_card *card, int online)
+{
+	snd_printd("snd card %s state change %d -> %d\n",
+		   card->shortname, !card->offline, online);
+	card->offline = !online;
+	/* make sure offline is updated prior to wake up */
+	wmb();
+	xchg(&card->offline_change, 1);
+	wake_up_interruptible(&card->offline_poll_wait);
+}
+EXPORT_SYMBOL(snd_card_change_online_state);
+
+/**
+ * snd_card_is_online_state - return true if card is online state
+ * @card: Card to query
+ */
+bool snd_card_is_online_state(struct snd_card *card)
+{
+	return !card->offline;
+}
+EXPORT_SYMBOL(snd_card_is_online_state);
+
 #ifdef CONFIG_PM
 /**
  *  snd_power_wait - wait until the power-state is changed.

sound/soc/soc-core.c

@@ -3271,6 +3271,17 @@ struct snd_soc_component *snd_soc_lookup_component(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(snd_soc_lookup_component);
 
+/**
+ * snd_soc_card_change_online_state - Mark if soc card is online/offline
+ *
+ * @soc_card : soc_card to mark
+ */
+void snd_soc_card_change_online_state(struct snd_soc_card *soc_card, int online)
+{
+	snd_card_change_online_state(soc_card->snd_card, online);
+}
+EXPORT_SYMBOL(snd_soc_card_change_online_state);
+
 /* Retrieve a card's name from device tree */
 int snd_soc_of_parse_card_name(struct snd_soc_card *card,
 			       const char *propname)