text: /**
   * Copyright (c) 2011 Jonathan Cameron
   *
   * 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.
   *
   * Companion module to the iio simple dummy example driver.
   * The purpose of this is to generate 'fake' event interrupts thus
   * allowing that driver's code to be as close as possible to that of
   * a normal driver talking to hardware.  The approach used here
   * is not intended to be general and just happens to work for this
   * particular use case.
   */
  
  #include <linux/kernel.h>
  #include <linux/slab.h>
  #include <linux/interrupt.h>
  #include <linux/irq.h>
  #include <linux/mutex.h>
  #include <linux/module.h>
  #include <linux/sysfs.h>
  
  #include "iio_dummy_evgen.h"
  #include "iio.h"
  #include "sysfs.h"
  
  /* Fiddly bit of faking and irq without hardware */
  #define IIO_EVENTGEN_NO 10
  /**
   * struct iio_dummy_evgen - evgen state
   * @chip: irq chip we are faking
   * @base: base of irq range
   * @enabled: mask of which irqs are enabled
   * @inuse: mask of which irqs actually have anyone connected
   * @lock: protect the evgen state
   */
  struct iio_dummy_eventgen {
  	struct irq_chip chip;
  	int base;
  	bool enabled[IIO_EVENTGEN_NO];
  	bool inuse[IIO_EVENTGEN_NO];
  	struct mutex lock;
  };
  
  /* We can only ever have one instance of this 'device' */
  static struct iio_dummy_eventgen *iio_evgen;
  static const char *iio_evgen_name = "iio_dummy_evgen";
  
  static void iio_dummy_event_irqmask(struct irq_data *d)
  {
  	struct irq_chip *chip = irq_data_get_irq_chip(d);
  	struct iio_dummy_eventgen *evgen =
  		container_of(chip, struct iio_dummy_eventgen, chip);
  
  	evgen->enabled[d->irq - evgen->base] = false;
  }
  
  static void iio_dummy_event_irqunmask(struct irq_data *d)
  {
  	struct irq_chip *chip = irq_data_get_irq_chip(d);
  	struct iio_dummy_eventgen *evgen =
  		container_of(chip, struct iio_dummy_eventgen, chip);
  
  	evgen->enabled[d->irq - evgen->base] = true;
  }
  
  static int iio_dummy_evgen_create(void)
  {
  	int ret, i;
  
  	iio_evgen = kzalloc(sizeof(*iio_evgen), GFP_KERNEL);
  	if (iio_evgen == NULL)
  		return -ENOMEM;
  
  	iio_evgen->base = irq_alloc_descs(-1, 0, IIO_EVENTGEN_NO, 0);
  	if (iio_evgen->base < 0) {
  		ret = iio_evgen->base;
  		kfree(iio_evgen);
  		return ret;
  	}
  	iio_evgen->chip.name = iio_evgen_name;
  	iio_evgen->chip.irq_mask = &iio_dummy_event_irqmask;
  	iio_evgen->chip.irq_unmask = &iio_dummy_event_irqunmask;
  	for (i = 0; i < IIO_EVENTGEN_NO; i++) {
  		irq_set_chip(iio_evgen->base + i, &iio_evgen->chip);
  		irq_set_handler(iio_evgen->base + i, &handle_simple_irq);
  		irq_modify_status(iio_evgen->base + i,
  				  IRQ_NOREQUEST | IRQ_NOAUTOEN,
  				  IRQ_NOPROBE);
  	}
  	mutex_init(&iio_evgen->lock);
  	return 0;
  }
  
  /**
   * iio_dummy_evgen_get_irq() - get an evgen provided irq for a device
   *
   * This function will give a free allocated irq to a client device.
   * That irq can then be caused to 'fire' by using the associated sysfs file.
   */
  int iio_dummy_evgen_get_irq(void)
  {
  	int i, ret = 0;
  
  	if (iio_evgen == NULL)
  		return -ENODEV;
  
  	mutex_lock(&iio_evgen->lock);
  	for (i = 0; i < IIO_EVENTGEN_NO; i++)
  		if (iio_evgen->inuse[i] == false) {
  			ret = iio_evgen->base + i;
  			iio_evgen->inuse[i] = true;
  			break;
  		}
  	mutex_unlock(&iio_evgen->lock);
  	if (i == IIO_EVENTGEN_NO)
  		return -ENOMEM;
  	return ret;
  }
  EXPORT_SYMBOL_GPL(iio_dummy_evgen_get_irq);
  
  /**
   * iio_dummy_evgen_release_irq() - give the irq back.
   * @irq: irq being returned to the pool
   *
   * Used by client driver instances to give the irqs back when they disconnect
   */
  int iio_dummy_evgen_release_irq(int irq)
  {
  	mutex_lock(&iio_evgen->lock);
  	iio_evgen->inuse[irq - iio_evgen->base] = false;
  	mutex_unlock(&iio_evgen->lock);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(iio_dummy_evgen_release_irq);
  
  static void iio_dummy_evgen_free(void)
  {
  	irq_free_descs(iio_evgen->base, IIO_EVENTGEN_NO);
  	kfree(iio_evgen);
  }
  
  static void iio_evgen_release(struct device *dev)
  {
  	iio_dummy_evgen_free();
  }
  
  static ssize_t iio_evgen_poke(struct device *dev,
  			      struct device_attribute *attr,
  			      const char *buf,
  			      size_t len)
  {
  	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
  
  	if (iio_evgen->enabled[this_attr->address])
  		handle_nested_irq(iio_evgen->base + this_attr->address);
  
  	return len;
  }
  
  static IIO_DEVICE_ATTR(poke_ev0, S_IWUSR, NULL, &iio_evgen_poke, 0);
  static IIO_DEVICE_ATTR(poke_ev1, S_IWUSR, NULL, &iio_evgen_poke, 1);
  static IIO_DEVICE_ATTR(poke_ev2, S_IWUSR, NULL, &iio_evgen_poke, 2);
  static IIO_DEVICE_ATTR(poke_ev3, S_IWUSR, NULL, &iio_evgen_poke, 3);
  static IIO_DEVICE_ATTR(poke_ev4, S_IWUSR, NULL, &iio_evgen_poke, 4);
  static IIO_DEVICE_ATTR(poke_ev5, S_IWUSR, NULL, &iio_evgen_poke, 5);
  static IIO_DEVICE_ATTR(poke_ev6, S_IWUSR, NULL, &iio_evgen_poke, 6);
  static IIO_DEVICE_ATTR(poke_ev7, S_IWUSR, NULL, &iio_evgen_poke, 7);
  static IIO_DEVICE_ATTR(poke_ev8, S_IWUSR, NULL, &iio_evgen_poke, 8);
  static IIO_DEVICE_ATTR(poke_ev9, S_IWUSR, NULL, &iio_evgen_poke, 9);
  
  static struct attribute *iio_evgen_attrs[] = {
  	&iio_dev_attr_poke_ev0.dev_attr.attr,
  	&iio_dev_attr_poke_ev1.dev_attr.attr,
  	&iio_dev_attr_poke_ev2.dev_attr.attr,
  	&iio_dev_attr_poke_ev3.dev_attr.attr,
  	&iio_dev_attr_poke_ev4.dev_attr.attr,
  	&iio_dev_attr_poke_ev5.dev_attr.attr,
  	&iio_dev_attr_poke_ev6.dev_attr.attr,
  	&iio_dev_attr_poke_ev7.dev_attr.attr,
  	&iio_dev_attr_poke_ev8.dev_attr.attr,
  	&iio_dev_attr_poke_ev9.dev_attr.attr,
  	NULL,
  };
  
  static const struct attribute_group iio_evgen_group = {
  	.attrs = iio_evgen_attrs,
  };
  
  static const struct attribute_group *iio_evgen_groups[] = {
  	&iio_evgen_group,
  	NULL
  };
  
  static struct device iio_evgen_dev = {
  	.bus = &iio_bus_type,
  	.groups = iio_evgen_groups,
  	.release = &iio_evgen_release,
  };
  static __init int iio_dummy_evgen_init(void)
  {
  	int ret = iio_dummy_evgen_create();
  	if (ret < 0)
  		return ret;
  	device_initialize(&iio_evgen_dev);
  	dev_set_name(&iio_evgen_dev, "iio_evgen");
  	return device_add(&iio_evgen_dev);
  }
  module_init(iio_dummy_evgen_init);
  
  static __exit void iio_dummy_evgen_exit(void)
  {
  	device_unregister(&iio_evgen_dev);
  }
  module_exit(iio_dummy_evgen_exit);
  
  MODULE_AUTHOR("Jonathan Cameron <jic23@cam.ac.uk>");
  MODULE_DESCRIPTION("IIO dummy driver");
  MODULE_LICENSE("GPL v2");
  