iio-trig-gpio.c

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/*
 * Industrial I/O - gpio based trigger support
 *
 * Copyright (c) 2008 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.
 *
 * Currently this is more of a functioning proof of concept than a full
 * fledged trigger driver.
 *
 * TODO:
 *
 * Add board config elements to allow specification of startup settings.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/interrupt.h>
#include <linux/gpio.h>
#include <linux/slab.h>

#include <linux/iio/iio.h>
#include <linux/iio/trigger.h>

static LIST_HEAD(iio_gpio_trigger_list);
static DEFINE_MUTEX(iio_gpio_trigger_list_lock);

struct iio_gpio_trigger_info {
    struct mutex in_use;
    unsigned int irq;
};
/*
 * Need to reference count these triggers and only enable gpio interrupts
 * as appropriate.
 */

/* So what functionality do we want in here?... */
/* set high / low as interrupt type? */

static irqreturn_t iio_gpio_trigger_poll(int irq, void *private)
{
    /* Timestamp not currently provided */
    iio_trigger_poll(private, 0);
    return IRQ_HANDLED;
}

static const struct iio_trigger_ops iio_gpio_trigger_ops = {
    .owner = THIS_MODULE,
};

static int __devinit iio_gpio_trigger_probe(struct platform_device *pdev)
{
    struct iio_gpio_trigger_info *trig_info;
    struct iio_trigger *trig, *trig2;
    unsigned long irqflags;
    struct resource *irq_res;
    int irq, ret = 0, irq_res_cnt = 0;

    do {
        irq_res = platform_get_resource(pdev,
                IORESOURCE_IRQ, irq_res_cnt);

        if (irq_res == NULL) {
            if (irq_res_cnt == 0)
                dev_err(&pdev->dev, "No GPIO IRQs specified");
            break;
        }
        irqflags = (irq_res->flags & IRQF_TRIGGER_MASK) | IRQF_SHARED;

        for (irq = irq_res->start; irq <= irq_res->end; irq++) {

            trig = iio_trigger_alloc("irqtrig%d", irq);
            if (!trig) {
                ret = -ENOMEM;
                goto error_free_completed_registrations;
            }

            trig_info = kzalloc(sizeof(*trig_info), GFP_KERNEL);
            if (!trig_info) {
                ret = -ENOMEM;
                goto error_put_trigger;
            }
            trig->private_data = trig_info;
            trig_info->irq = irq;
            trig->ops = &iio_gpio_trigger_ops;
            ret = request_irq(irq, iio_gpio_trigger_poll,
                      irqflags, trig->name, trig);
            if (ret) {
                dev_err(&pdev->dev,
                    "request IRQ-%d failed", irq);
                goto error_free_trig_info;
            }

            ret = iio_trigger_register(trig);
            if (ret)
                goto error_release_irq;

            list_add_tail(&trig->alloc_list,
                    &iio_gpio_trigger_list);
        }

        irq_res_cnt++;
    } while (irq_res != NULL);


    return 0;

/* First clean up the partly allocated trigger */
error_release_irq:
    free_irq(irq, trig);
error_free_trig_info:
    kfree(trig_info);
error_put_trigger:
    iio_trigger_put(trig);
error_free_completed_registrations:
    /* The rest should have been added to the iio_gpio_trigger_list */
    list_for_each_entry_safe(trig,
                 trig2,
                 &iio_gpio_trigger_list,
                 alloc_list) {
        trig_info = trig->private_data;
        free_irq(gpio_to_irq(trig_info->irq), trig);
        kfree(trig_info);
        iio_trigger_unregister(trig);
    }

    return ret;
}

static int __devexit iio_gpio_trigger_remove(struct platform_device *pdev)
{
    struct iio_trigger *trig, *trig2;
    struct iio_gpio_trigger_info *trig_info;

    mutex_lock(&iio_gpio_trigger_list_lock);
    list_for_each_entry_safe(trig,
                 trig2,
                 &iio_gpio_trigger_list,
                 alloc_list) {
        trig_info = trig->private_data;
        iio_trigger_unregister(trig);
        free_irq(trig_info->irq, trig);
        kfree(trig_info);
        iio_trigger_put(trig);
    }
    mutex_unlock(&iio_gpio_trigger_list_lock);

    return 0;
}

static struct platform_driver iio_gpio_trigger_driver = {
    .probe = iio_gpio_trigger_probe,
    .remove = __devexit_p(iio_gpio_trigger_remove),
    .driver = {
        .name = "iio_gpio_trigger",
        .owner = THIS_MODULE,
    },
};

module_platform_driver(iio_gpio_trigger_driver);

MODULE_AUTHOR("Jonathan Cameron <[email protected]>");
MODULE_DESCRIPTION("Example gpio trigger for the iio subsystem");
MODULE_LICENSE("GPL v2");