// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2011 Jonathan Cameron
 *
 * 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 <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/irq_sim.h>

/* Fiddly bit of faking and irq without hardware */
#define IIO_EVENTGEN_NO 10

/**
 * struct iio_dummy_eventgen - event generator specific state
 * @regs: irq regs we are faking
 * @lock: protect the evgen state
 * @inuse: mask of which irqs are connected
 * @irq_sim_domain: irq simulator domain
 */
struct iio_dummy_eventgen {
        struct iio_dummy_regs regs[IIO_EVENTGEN_NO];
        struct mutex lock;
        bool inuse[IIO_EVENTGEN_NO];
        struct irq_domain *irq_sim_domain;
};

/* We can only ever have one instance of this 'device' */
static struct iio_dummy_eventgen *iio_evgen;

static int iio_dummy_evgen_create(void)
{
        int ret;

        iio_evgen = kzalloc_obj(*iio_evgen);
        if (!iio_evgen)
                return -ENOMEM;

        iio_evgen->irq_sim_domain = irq_domain_create_sim(NULL,
                                                          IIO_EVENTGEN_NO);
        if (IS_ERR(iio_evgen->irq_sim_domain)) {
                ret = PTR_ERR(iio_evgen->irq_sim_domain);
                kfree(iio_evgen);
                return ret;
        }

        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)
                return -ENODEV;

        mutex_lock(&iio_evgen->lock);
        for (i = 0; i < IIO_EVENTGEN_NO; i++) {
                if (!iio_evgen->inuse[i]) {
                        ret = irq_create_mapping(iio_evgen->irq_sim_domain, 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
 */
void iio_dummy_evgen_release_irq(int irq)
{
        struct irq_data *irqd = irq_get_irq_data(irq);

        mutex_lock(&iio_evgen->lock);
        iio_evgen->inuse[irqd_to_hwirq(irqd)] = false;
        irq_dispose_mapping(irq);
        mutex_unlock(&iio_evgen->lock);
}
EXPORT_SYMBOL_GPL(iio_dummy_evgen_release_irq);

struct iio_dummy_regs *iio_dummy_evgen_get_regs(int irq)
{
        struct irq_data *irqd = irq_get_irq_data(irq);

        return &iio_evgen->regs[irqd_to_hwirq(irqd)];

}
EXPORT_SYMBOL_GPL(iio_dummy_evgen_get_regs);

static void iio_dummy_evgen_free(void)
{
        irq_domain_remove_sim(iio_evgen->irq_sim_domain);
        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);
        unsigned long event;
        int ret, irq;

        ret = kstrtoul(buf, 10, &event);
        if (ret)
                return ret;

        iio_evgen->regs[this_attr->address].reg_id   = this_attr->address;
        iio_evgen->regs[this_attr->address].reg_data = event;

        irq = irq_find_mapping(iio_evgen->irq_sim_domain, this_attr->address);
        ret = irq_set_irqchip_state(irq, IRQCHIP_STATE_PENDING, true);
        if (ret)
                return ret;

        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");
        ret = device_add(&iio_evgen_dev);
        if (ret)
                put_device(&iio_evgen_dev);
        return ret;
}
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@kernel.org>");
MODULE_DESCRIPTION("IIO dummy driver");
MODULE_LICENSE("GPL v2");