iio: Add helper function for initializing triggered buffers

Add a helper function for executing the common tasks which are usually involved
in setting up a simple software ringbuffer. It will allocate the buffer,
allocate the pollfunc and register the buffer.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/iio/Kconfig

diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index 103349f..612073f 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -30,6 +30,13 @@
 	  no buffer events so it is up to userspace to work out how
 	  often to read from the buffer.
 
+config IIO_TRIGGERED_BUFFER
+	tristate
+	select IIO_TRIGGER
+	select IIO_KFIFO_BUF
+	help
+	  Provides helper functions for setting up triggered buffers.
+
 endif # IIO_BUFFER
 
 config IIO_TRIGGER