Two threads can try to fire the irq_sim with different offsets and will
end up fighting for the irq_work asignment. Thomas Gleixner suggested a
solution based on a bitfield where we set a bit for every offset
associated with an interrupt that should be fired and then iterate over
all set bits in the interrupt handler.

This is a slightly modified solution using a bitmap so that we don't
impose a limit on the number of interrupts one can allocate with
irq_sim.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

There is the SPDX license identifier now in the irq simulator. Remove the
license boilerplate.

While at it: update the copyright notice, since I did some changes in 2018.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20180426200747.8344-1-brgl@bgdev.pl

Add SPDX identifiers to files

 - which contain an explicit license boiler plate or reference

 - which do not contain a license reference and were not updated in the
   initial SPDX conversion because the license was deduced by the scanners
   via EXPORT_SYMBOL_GPL as GPL2.0 only.

[ tglx: Moved adding identifiers from the patch which removes the
  	references/boilerplate ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Link: https://lkml.kernel.org/r/20180314212030.668321222@linutronix.de

Returning the base of the allocated interrupt range from irq_sim_init() and
devm_irq_sim_init() allows users to handle the logic of associating irq
numbers with any other driver-specific resources without having to use
irq_sim_irqnum().

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/20180304121018.640-4-brgl@bgdev.pl

As discussed with Marc Zyngier: irq_sim_init() and its devres variant
should return the base of the allocated interrupt range on success rather
than 0.

Make devm_irq_sim_init() check for an error code. This is a preparatory
change for modifying irq_sim_init() itself.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/20180304121018.640-3-brgl@bgdev.pl

kfree() is used in the irq_sim code but slab.h is pulled in indirectly via
irq.h. Include it explicitly.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/20180304121018.640-2-brgl@bgdev.pl

Add a resource managed version of irq_sim_init(). This can be
conveniently used in device drivers.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: linux-doc@vger.kernel.org
Cc: linux-gpio@vger.kernel.org
Cc: Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>
Cc: Jonathan Cameron <jic23@kernel.org>
Link: http://lkml.kernel.org/r/20170814145318.6495-3-brgl@bgdev.pl
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Implement a simple, irq_work-based framework for simulating
interrupts. Currently the API exposes routines for initializing and
deinitializing the simulator object, enqueueing the interrupts and
retrieving the allocated interrupt numbers based on the offset of the
dummy interrupt in the simulator struct.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: linux-doc@vger.kernel.org
Cc: linux-gpio@vger.kernel.org
Cc: Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>
Cc: Jonathan Cameron <jic23@kernel.org>
Link: http://lkml.kernel.org/r/20170814145318.6495-2-brgl@bgdev.pl
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>