treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500

Based on 2 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation #

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 4122 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Enrico Weigelt <info@metux.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

iio: make function argument and some structures const

Make the argument of the functions iio_sw{d/t}_group_init_type_name const
as they are only passed to the function config_group_init_type_name having
the argument as const.

Make the config_item_type structures const as they are either passed to
the functions having the argument as const or they are
stored in the const "ci_type" field of a config_item structure.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

iio:configfs: Introduce iio/configfs.h to provide a location for the configfs_subsystem

This exported element needs to be accesible to all drivers using configfs
within IIO. Previously it was in the sw_trig.h file which only convered one
such usecase. This also fixes a sparse warning as it is now in a header
that makes sense to include from industrialio-configfs.c

Signed-off-by: Jonathan Cameron < jic23@kernel.org>

iio: core: Introduce IIO configfs support

This patch creates the IIO configfs root group. The group
will appear under <mount-point>/iio/, usually /config/iio.

We introduce configfs support in IIO in order to be able to easily
create IIO objects from userspace. The first supported IIO objects
are triggers introduced with next patches.

Signed-off-by: Daniel Baluta <daniel.baluta@intel.com>
Tested-by: Matt Ranostay <matt.ranostay@intel>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>