iio: Support triggered events

Support triggered events.

This is useful for chips that don't have their own interrupt sources.
It allows to use generic/standalone iio triggers for those drivers.

Signed-off-by: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index 3c6c6e2..6fe0d65 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -38,6 +38,12 @@
 	This value controls the maximum number of consumers that a
 	given trigger may handle. Default is 2.
 
+config IIO_TRIGGERED_EVENT
+	tristate
+	select IIO_TRIGGER
+	help
+	  Provides helper functions for setting up triggered events.
+
 source "drivers/iio/accel/Kconfig"
 source "drivers/iio/adc/Kconfig"
 source "drivers/iio/amplifiers/Kconfig"