ASoC: Add a notifier for jack status changes

Some systems provide both mechanical and electrical detection of jack
status changes. On such systems power savings can be achieved by only
enabling the electrical detection methods when physical insertion has
been detected.

Begin supporting such systems by providing a notifier for jack status
changes which can be used to trigger any reconfiguration.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>

include/sound/soc.h

@@ -15,6 +15,7 @@
 
 #include <linux/platform_device.h>
 #include <linux/types.h>
+#include <linux/notifier.h>
 #include <linux/workqueue.h>
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
@@ -261,6 +262,10 @@ int snd_soc_jack_new(struct snd_soc_card *card, const char *id, int type,
 void snd_soc_jack_report(struct snd_soc_jack *jack, int status, int mask);
 int snd_soc_jack_add_pins(struct snd_soc_jack *jack, int count,
 			  struct snd_soc_jack_pin *pins);
+void snd_soc_jack_notifier_register(struct snd_soc_jack *jack,
+				    struct notifier_block *nb);
+void snd_soc_jack_notifier_unregister(struct snd_soc_jack *jack,
+				      struct notifier_block *nb);
 #ifdef CONFIG_GPIOLIB
 int snd_soc_jack_add_gpios(struct snd_soc_jack *jack, int count,
 			struct snd_soc_jack_gpio *gpios);
@@ -364,6 +369,7 @@ struct snd_soc_jack {
 	struct snd_soc_card *card;
 	struct list_head pins;
 	int status;
+	struct blocking_notifier_head notifier;
 };
 
 /* SoC PCM stream information */

sound/soc/soc-jack.c

@@ -37,6 +37,7 @@ int snd_soc_jack_new(struct snd_soc_card *card, const char *id, int type,
 {
 	jack->card = card;
 	INIT_LIST_HEAD(&jack->pins);
+	BLOCKING_INIT_NOTIFIER_HEAD(&jack->notifier);
 
 	return snd_jack_new(card->codec->card, id, type, &jack->jack);
 }
@@ -93,6 +94,9 @@ void snd_soc_jack_report(struct snd_soc_jack *jack, int status, int mask)
 			snd_soc_dapm_disable_pin(codec, pin->pin);
 	}
 
+	/* Report before the DAPM sync to help users updating micbias status */
+	blocking_notifier_call_chain(&jack->notifier, status, NULL);
+
 	snd_soc_dapm_sync(codec);
 
 	snd_jack_report(jack->jack, status);
@@ -143,6 +147,40 @@ int snd_soc_jack_add_pins(struct snd_soc_jack *jack, int count,
 }
 EXPORT_SYMBOL_GPL(snd_soc_jack_add_pins);
 
+/**
+ * snd_soc_jack_notifier_register - Register a notifier for jack status
+ *
+ * @jack:  ASoC jack
+ * @nb:    Notifier block to register
+ *
+ * Register for notification of the current status of the jack.  Note
+ * that it is not possible to report additional jack events in the
+ * callback from the notifier, this is intended to support
+ * applications such as enabling electrical detection only when a
+ * mechanical detection event has occurred.
+ */
+void snd_soc_jack_notifier_register(struct snd_soc_jack *jack,
+				    struct notifier_block *nb)
+{
+	blocking_notifier_chain_register(&jack->notifier, nb);
+}
+EXPORT_SYMBOL_GPL(snd_soc_jack_notifier_register);
+
+/**
+ * snd_soc_jack_notifier_unregister - Unregister a notifier for jack status
+ *
+ * @jack:  ASoC jack
+ * @nb:    Notifier block to unregister
+ *
+ * Stop notifying for status changes.
+ */
+void snd_soc_jack_notifier_unregister(struct snd_soc_jack *jack,
+				      struct notifier_block *nb)
+{
+	blocking_notifier_chain_unregister(&jack->notifier, nb);
+}
+EXPORT_SYMBOL_GPL(snd_soc_jack_notifier_unregister);
+
 #ifdef CONFIG_GPIOLIB
 /* gpio detect */
 static void snd_soc_jack_gpio_detect(struct snd_soc_jack_gpio *gpio)