Staging: IIO: Trigger support added to core.

Add general registration support for IIO triggers.  These
are currently only used to initialize a 'poll' of a given
device.  Examples include the lis3l02dq's data ready signal
being used to initialize a read and gpio triggers being
used to allow externally synchronized sensor reading.

Each trigger can cause any number of 'consumer' devices
to be polled with each storing data into a related ring
buffer.

Two stage triggering is supported with 'fast' and 'slow'
paths.  The first is used for things like pulling a data
hold line high and the second for actual read which
may take far longer.

Changes since V2:
* As with IIO triggers now use a registration approach
  much closer to that of input leading to cleaner code.

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/Kconfig

@@ -17,6 +17,14 @@ config IIO_RING_BUFFER
 	  Provide core support for various ring buffer based data
 	  acquisition methods.
 
+config IIO_TRIGGER
+	boolean "Enable triggered sampling support"
+	help
+	  Provides IIO core support for triggers.  Currently these
+	  are used to initialize capture of samples to push into
+	  ring buffers.  The triggers are effectively a 'capture
+	  data now' interrupt.
+
 source "drivers/staging/iio/accel/Kconfig"
 source "drivers/staging/iio/adc/Kconfig"
 source "drivers/staging/iio/light/Kconfig"

drivers/staging/iio/Makefile

@@ -5,6 +5,7 @@
 obj-$(CONFIG_IIO) += industrialio.o
 industrialio-y := industrialio-core.o
 industrialio-$(CONFIG_IIO_RING_BUFFER) += industrialio-ring.o
+industrialio-$(CONFIG_IIO_TRIGGER) += industrialio-trigger.o
 
 obj-y += accel/
 obj-y += adc/