iio: trigger: Add filter callback

Allow devices to reject triggers and vice versa.

Changes since V1:
Added kernel-doc
Moved callback into iio_info
Changed function naming
Revised return value passing
Add forward declaration to avoid warnings

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/iio.h

@@ -204,6 +204,8 @@ static inline s64 iio_get_time_ns(void)
 #define IIO_VAL_INT_PLUS_MICRO 2
 #define IIO_VAL_INT_PLUS_NANO 3
 
+struct iio_trigger; /* forward declaration */
+
 /**
  * struct iio_info - constant information about device
  * @driver_module:	module structure used to ensure correct
@@ -224,6 +226,8 @@ static inline s64 iio_get_time_ns(void)
  *			is event dependant. event_code specifies which event.
  * @write_event_value:	write the value associate with the event.
  *			Meaning is event dependent.
+ * @validate_trigger:	function to validate the trigger when the
+ *			current trigger gets changed.
  **/
 struct iio_info {
 	struct module			*driver_module;
@@ -256,6 +260,9 @@ struct iio_info {
 	int (*write_event_value)(struct iio_dev *indio_dev,
 				 int event_code,
 				 int val);
+	int (*validate_trigger)(struct iio_dev *indio_dev,
+				struct iio_trigger *trig);
+
 };
 
 /**

drivers/staging/iio/industrialio-trigger.c

@@ -340,6 +340,9 @@ static ssize_t iio_trigger_write_current(struct device *dev,
 {
 	struct iio_dev *dev_info = dev_get_drvdata(dev);
 	struct iio_trigger *oldtrig = dev_info->trig;
+	struct iio_trigger *trig;
+	int ret;
+
 	mutex_lock(&dev_info->mlock);
 	if (dev_info->currentmode == INDIO_RING_TRIGGERED) {
 		mutex_unlock(&dev_info->mlock);
@@ -347,7 +350,22 @@ static ssize_t iio_trigger_write_current(struct device *dev,
 	}
 	mutex_unlock(&dev_info->mlock);
 
-	dev_info->trig = iio_trigger_find_by_name(buf, len);
+	trig = iio_trigger_find_by_name(buf, len);
+
+	if (trig && dev_info->info->validate_trigger) {
+		ret = dev_info->info->validate_trigger(dev_info, trig);
+		if (ret)
+			return ret;
+	}
+
+	if (trig && trig->validate_device) {
+		ret = trig->validate_device(trig, dev_info);
+		if (ret)
+			return ret;
+	}
+
+	dev_info->trig = trig;
+
 	if (oldtrig && dev_info->trig != oldtrig)
 		iio_put_trigger(oldtrig);
 	if (dev_info->trig)

drivers/staging/iio/trigger.h

@@ -29,6 +29,8 @@ struct iio_subirq {
  * @set_trigger_state:	[DRIVER] switch on/off the trigger on demand
  * @try_reenable:	function to reenable the trigger when the
  *			use count is zero (may be NULL)
+ * @validate_device:	function to validate the device when the
+ *			current trigger gets changed.
  * @subirq_chip:	[INTERN] associate 'virtual' irq chip.
  * @subirq_base:	[INTERN] base number for irqs provided by trigger.
  * @subirqs:		[INTERN] information about the 'child' irqs.
@@ -48,6 +50,8 @@ struct iio_trigger {
 
 	int (*set_trigger_state)(struct iio_trigger *trig, bool state);
 	int (*try_reenable)(struct iio_trigger *trig);
+	int (*validate_device)(struct iio_trigger *trig,
+			       struct iio_dev *indio_dev);
 
 	struct irq_chip			subirq_chip;
 	int				subirq_base;