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.

Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>
Signed-off-by: Sudheer Papothi <spapothi@codeaurora.org>

5 files changed, 103 insertions, 2 deletions

diff --git a/include/sound/core.h b/include/sound/core.h
index cdfecafff0f4..7b05f88cacac 100644
--- a/include/sound/core.h
+++ b/include/sound/core.h
@@ -134,6 +134,9 @@ struct snd_card {
 	struct device card_dev;		/* cardX object for sysfs */
 	const struct attribute_group *dev_groups[4]; /* assigned sysfs attr */
 	bool registered;		/* card_dev is registered? */
+	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 */
@@ -265,6 +268,8 @@ 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))
 
diff --git a/include/sound/soc.h b/include/sound/soc.h
index d696c2f6bcbb..eb030bad423e 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -553,12 +553,13 @@ int snd_soc_update_bits_locked(struct snd_soc_codec *codec,
 int snd_soc_test_bits(struct snd_soc_codec *codec, unsigned int reg,
 				unsigned int mask, unsigned int value);
 
+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_codec(struct snd_soc_codec *codec);
 struct snd_ac97 *snd_soc_new_ac97_codec(struct snd_soc_codec *codec,
 	unsigned int id, unsigned int id_mask);
 void snd_soc_free_ac97_codec(struct snd_ac97 *ac97);
-
 int snd_soc_set_ac97_ops(struct snd_ac97_bus_ops *ops);
 int snd_soc_set_ac97_ops_of_reset(struct snd_ac97_bus_ops *ops,
 		struct platform_device *pdev);
diff --git a/sound/core/init.c b/sound/core/init.c
index 20f37fb3800e..f413963c414f 100644
--- a/sound/core/init.c
+++ b/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 */
@@ -258,6 +301,7 @@ int snd_card_new(struct device *parent, int idx, const char *xid,
 	init_waitqueue_head(&card->power_sleep);
 #endif
 
+	init_waitqueue_head(&card->offline_poll_wait);
 	device_initialize(&card->card_dev);
 	card->card_dev.parent = parent;
 	card->card_dev.class = sound_class;
@@ -972,6 +1016,35 @@ 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.
diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index 24cb33a9f5c8..e28f0f9e6e99 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -3039,6 +3039,17 @@ static int snd_soc_codec_set_bias_level(struct snd_soc_dapm_context *dapm,
 }
 
 /**
+ * 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);
+
+/**
  * snd_soc_register_codec - Register a codec with the ASoC core
  *
  * @dev: The parent device for this codec
diff --git a/sound/soc/soc-io.c b/sound/soc/soc-io.c
index 9b3939049cef..a90a1630ab1c 100644
--- a/sound/soc/soc-io.c
+++ b/sound/soc/soc-io.c
@@ -195,9 +195,14 @@ EXPORT_SYMBOL_GPL(snd_soc_component_test_bits);
 
 unsigned int snd_soc_read(struct snd_soc_codec *codec, unsigned int reg)
 {
+	struct snd_card *snd_card = codec->component.card->snd_card;
 	unsigned int val;
 	int ret;
 
+	if (unlikely(!snd_card_is_online_state(snd_card))) {
+		dev_err(codec->dev, "read 0x%02x while offline\n", reg);
+		return -ENODEV;
+	}
 	ret = snd_soc_component_read(&codec->component, reg, &val);
 	if (ret < 0)
 		return -1;
@@ -209,6 +214,12 @@ EXPORT_SYMBOL_GPL(snd_soc_read);
 int snd_soc_write(struct snd_soc_codec *codec, unsigned int reg,
 	unsigned int val)
 {
+	struct snd_card *snd_card = codec->component.card->snd_card;
+
+	if (unlikely(!snd_card_is_online_state(snd_card))) {
+		dev_err(codec->dev, "write 0x%02x while offline\n", reg);
+		return -ENODEV;
+	}
 	return snd_soc_component_write(&codec->component, reg, val);
 }
 EXPORT_SYMBOL_GPL(snd_soc_write);