iio: Rename iio_trigger_poll_chained and add kernel-doc

Rename the function to iio_trigger_poll_nested. Add kernel-doc with
a note on the context where the function is expected to be called.

Signed-off-by: Mehdi Djait <mehdi.djait.k@gmail.com>
Link: https://lore.kernel.org/r/841b533cba28ca25a8e87280c44e45979166e8e2.1677761379.git.mehdi.djait.k@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: set default trig->dev.parent

When allocated with [devm_]iio_trigger_alloc(), set trig device parent to
the device the trigger is allocated for by default.

It can always be reassigned in the probe routine.

Change iio_trigger_alloc() API to add the device pointer to be coherent
with devm_iio_trigger_alloc, using similar interface to
iio_device_alloc().

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20210309193620.2176163-2-gwendal@chromium.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 177

Based on 1 normalized pattern(s):

licensed under the gpl 2

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 135 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Reviewed-by: Steve Winslow <swinslow@gmail.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190528170026.071193225@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

iio: remove redundant unlikely annotation

unlikely has already included in IS_ERR(),
so just remove redundant unlikely annotation.

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

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:triggers: drop assign iio_info.driver_module and iio_trigger_ops.owner

The equivalent of both of these are now done via macro magic when
the relevant register calls are made. The actual structure
elements will shortly go away.

Note that stm32-timer-trigger has expanded rather beyond triggers
(to include encoder input counting for example) and hence has an
iio_info structure.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>

iio:trigger: Experimental kthread tight loop trigger (thread only)

This patch is in response to that of
Gregor Boirie <gregor.boirie@parrot.com>
who proposed using a tight kthread within a device driver (be it with the
support factored out into a helper library) in order to basically spin as
fast as possible.

It is meant as a talking point rather than a formal proposal of the code
(though we are heading towards that I think).
Also gives people some working code to mess around with.

I proposed that this could be done with a trigger with a few constraints
and this is the proof (be it ugly) of that.

There are some constraints though, some of which we would want to relax
if this were to move forward.

* Will only run the thread part of the registered pollfunc. This is to
avoid the overhead of jumping in and out of interrupt context. Is the
overhead significant? Not certain but feels like it should be!

* This limitation precludes any device that 'must' do some work in
interrupt context. However, that is true of few if any drivers and
I suspect that any that do will be restricted to using triggers they
provide themselves. Usually we have a top half mainly to grab a
timestamp as soon after the dataready type signal as possible.

Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Acked-by: Daniel Baluta <daniel.baluta@intel.com>