hid-roccat.c

Go to the documentation of this file.

/*
 * Roccat driver for Linux
 *
 * Copyright (c) 2010 Stefan Achatz <[email protected]>
 */

/*
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 */

/*
 * Module roccat is a char device used to report special events of roccat
 * hardware to userland. These events include requests for on-screen-display of
 * profile or dpi settings or requests for execution of macro sequences that are
 * not stored in device. The information in these events depends on hid device
 * implementation and contains data that is not available in a single hid event
 * or else hidraw could have been used.
 * It is inspired by hidraw, but uses only one circular buffer for all readers.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/cdev.h>
#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/hid-roccat.h>
#include <linux/module.h>

#define ROCCAT_FIRST_MINOR 0
#define ROCCAT_MAX_DEVICES 8

/* should be a power of 2 for performance reason */
#define ROCCAT_CBUF_SIZE 16

struct roccat_report {
    uint8_t *value;
};

struct roccat_device {
    unsigned int minor;
    int report_size;
    int open;
    int exist;
    wait_queue_head_t wait;
    struct device *dev;
    struct hid_device *hid;
    struct list_head readers;
    /* protects modifications of readers list */
    struct mutex readers_lock;

    /*
     * circular_buffer has one writer and multiple readers with their own
     * read pointers
     */
    struct roccat_report cbuf[ROCCAT_CBUF_SIZE];
    int cbuf_end;
    struct mutex cbuf_lock;
};

struct roccat_reader {
    struct list_head node;
    struct roccat_device *device;
    int cbuf_start;
};

static int roccat_major;
static struct cdev roccat_cdev;

static struct roccat_device *devices[ROCCAT_MAX_DEVICES];
/* protects modifications of devices array */
static DEFINE_MUTEX(devices_lock);

static ssize_t roccat_read(struct file *file, char __user *buffer,
        size_t count, loff_t *ppos)
{
    struct roccat_reader *reader = file->private_data;
    struct roccat_device *device = reader->device;
    struct roccat_report *report;
    ssize_t retval = 0, len;
    DECLARE_WAITQUEUE(wait, current);

    mutex_lock(&device->cbuf_lock);

    /* no data? */
    if (reader->cbuf_start == device->cbuf_end) {
        add_wait_queue(&device->wait, &wait);
        set_current_state(TASK_INTERRUPTIBLE);

        /* wait for data */
        while (reader->cbuf_start == device->cbuf_end) {
            if (file->f_flags & O_NONBLOCK) {
                retval = -EAGAIN;
                break;
            }
            if (signal_pending(current)) {
                retval = -ERESTARTSYS;
                break;
            }
            if (!device->exist) {
                retval = -EIO;
                break;
            }

            mutex_unlock(&device->cbuf_lock);
            schedule();
            mutex_lock(&device->cbuf_lock);
            set_current_state(TASK_INTERRUPTIBLE);
        }

        set_current_state(TASK_RUNNING);
        remove_wait_queue(&device->wait, &wait);
    }

    /* here we either have data or a reason to return if retval is set */
    if (retval)
        goto exit_unlock;

    report = &device->cbuf[reader->cbuf_start];
    /*
     * If report is larger than requested amount of data, rest of report
     * is lost!
     */
    len = device->report_size > count ? count : device->report_size;

    if (copy_to_user(buffer, report->value, len)) {
        retval = -EFAULT;
        goto exit_unlock;
    }
    retval += len;
    reader->cbuf_start = (reader->cbuf_start + 1) % ROCCAT_CBUF_SIZE;

exit_unlock:
    mutex_unlock(&device->cbuf_lock);
    return retval;
}

static unsigned int roccat_poll(struct file *file, poll_table *wait)
{
    struct roccat_reader *reader = file->private_data;
    poll_wait(file, &reader->device->wait, wait);
    if (reader->cbuf_start != reader->device->cbuf_end)
        return POLLIN | POLLRDNORM;
    if (!reader->device->exist)
        return POLLERR | POLLHUP;
    return 0;
}

static int roccat_open(struct inode *inode, struct file *file)
{
    unsigned int minor = iminor(inode);
    struct roccat_reader *reader;
    struct roccat_device *device;
    int error = 0;

    reader = kzalloc(sizeof(struct roccat_reader), GFP_KERNEL);
    if (!reader)
        return -ENOMEM;

    mutex_lock(&devices_lock);

    device = devices[minor];

    if (!device) {
        pr_emerg("roccat device with minor %d doesn't exist\n", minor);
        error = -ENODEV;
        goto exit_err_devices;
    }

    mutex_lock(&device->readers_lock);

    if (!device->open++) {
        /* power on device on adding first reader */
        error = hid_hw_power(device->hid, PM_HINT_FULLON);
        if (error < 0) {
            --device->open;
            goto exit_err_readers;
        }

        error = hid_hw_open(device->hid);
        if (error < 0) {
            hid_hw_power(device->hid, PM_HINT_NORMAL);
            --device->open;
            goto exit_err_readers;
        }
    }

    reader->device = device;
    /* new reader doesn't get old events */
    reader->cbuf_start = device->cbuf_end;

    list_add_tail(&reader->node, &device->readers);
    file->private_data = reader;

exit_err_readers:
    mutex_unlock(&device->readers_lock);
exit_err_devices:
    mutex_unlock(&devices_lock);
    if (error)
        kfree(reader);
    return error;
}

static int roccat_release(struct inode *inode, struct file *file)
{
    unsigned int minor = iminor(inode);
    struct roccat_reader *reader = file->private_data;
    struct roccat_device *device;

    mutex_lock(&devices_lock);

    device = devices[minor];
    if (!device) {
        mutex_unlock(&devices_lock);
        pr_emerg("roccat device with minor %d doesn't exist\n", minor);
        return -ENODEV;
    }

    mutex_lock(&device->readers_lock);
    list_del(&reader->node);
    mutex_unlock(&device->readers_lock);
    kfree(reader);

    if (!--device->open) {
        /* removing last reader */
        if (device->exist) {
            hid_hw_power(device->hid, PM_HINT_NORMAL);
            hid_hw_close(device->hid);
        } else {
            kfree(device);
        }
    }

    mutex_unlock(&devices_lock);

    return 0;
}

/*
 * roccat_report_event() - output data to readers
 * @minor: minor device number returned by roccat_connect()
 * @data: pointer to data
 * @len: size of data
 *
 * Return value is zero on success, a negative error code on failure.
 *
 * This is called from interrupt handler.
 */
int roccat_report_event(int minor, u8 const *data)
{
    struct roccat_device *device;
    struct roccat_reader *reader;
    struct roccat_report *report;
    uint8_t *new_value;

    device = devices[minor];

    new_value = kmemdup(data, device->report_size, GFP_ATOMIC);
    if (!new_value)
        return -ENOMEM;

    report = &device->cbuf[device->cbuf_end];

    /* passing NULL is safe */
    kfree(report->value);

    report->value = new_value;
    device->cbuf_end = (device->cbuf_end + 1) % ROCCAT_CBUF_SIZE;

    list_for_each_entry(reader, &device->readers, node) {
        /*
         * As we already inserted one element, the buffer can't be
         * empty. If start and end are equal, buffer is full and we
         * increase start, so that slow reader misses one event, but
         * gets the newer ones in the right order.
         */
        if (reader->cbuf_start == device->cbuf_end)
            reader->cbuf_start = (reader->cbuf_start + 1) % ROCCAT_CBUF_SIZE;
    }

    wake_up_interruptible(&device->wait);
    return 0;
}
EXPORT_SYMBOL_GPL(roccat_report_event);

/*
 * roccat_connect() - create a char device for special event output
 * @class: the class thats used to create the device. Meant to hold device
 * specific sysfs attributes.
 * @hid: the hid device the char device should be connected to.
 *
 * Return value is minor device number in Range [0, ROCCAT_MAX_DEVICES] on
 * success, a negative error code on failure.
 */
int roccat_connect(struct class *klass, struct hid_device *hid, int report_size)
{
    unsigned int minor;
    struct roccat_device *device;
    int temp;

    device = kzalloc(sizeof(struct roccat_device), GFP_KERNEL);
    if (!device)
        return -ENOMEM;

    mutex_lock(&devices_lock);

    for (minor = 0; minor < ROCCAT_MAX_DEVICES; ++minor) {
        if (devices[minor])
            continue;
        break;
    }

    if (minor < ROCCAT_MAX_DEVICES) {
        devices[minor] = device;
    } else {
        mutex_unlock(&devices_lock);
        kfree(device);
        return -EINVAL;
    }

    device->dev = device_create(klass, &hid->dev,
            MKDEV(roccat_major, minor), NULL,
            "%s%s%d", "roccat", hid->driver->name, minor);

    if (IS_ERR(device->dev)) {
        devices[minor] = NULL;
        mutex_unlock(&devices_lock);
        temp = PTR_ERR(device->dev);
        kfree(device);
        return temp;
    }

    mutex_unlock(&devices_lock);

    init_waitqueue_head(&device->wait);
    INIT_LIST_HEAD(&device->readers);
    mutex_init(&device->readers_lock);
    mutex_init(&device->cbuf_lock);
    device->minor = minor;
    device->hid = hid;
    device->exist = 1;
    device->cbuf_end = 0;
    device->report_size = report_size;

    return minor;
}
EXPORT_SYMBOL_GPL(roccat_connect);

/* roccat_disconnect() - remove char device from hid device
 * @minor: the minor device number returned by roccat_connect()
 */
void roccat_disconnect(int minor)
{
    struct roccat_device *device;

    mutex_lock(&devices_lock);
    device = devices[minor];
    mutex_unlock(&devices_lock);

    device->exist = 0; /* TODO exist maybe not needed */

    device_destroy(device->dev->class, MKDEV(roccat_major, minor));

    mutex_lock(&devices_lock);
    devices[minor] = NULL;
    mutex_unlock(&devices_lock);
    
    if (device->open) {
        hid_hw_close(device->hid);
        wake_up_interruptible(&device->wait);
    } else {
        kfree(device);
    }
}
EXPORT_SYMBOL_GPL(roccat_disconnect);

static long roccat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    struct inode *inode = file->f_path.dentry->d_inode;
    struct roccat_device *device;
    unsigned int minor = iminor(inode);
    long retval = 0;

    mutex_lock(&devices_lock);

    device = devices[minor];
    if (!device) {
        retval = -ENODEV;
        goto out;
    }

    switch (cmd) {
    case ROCCATIOCGREPSIZE:
        if (put_user(device->report_size, (int __user *)arg))
            retval = -EFAULT;
        break;
    default:
        retval = -ENOTTY;
    }
out:
    mutex_unlock(&devices_lock);
    return retval;
}

static const struct file_operations roccat_ops = {
    .owner = THIS_MODULE,
    .read = roccat_read,
    .poll = roccat_poll,
    .open = roccat_open,
    .release = roccat_release,
    .llseek = noop_llseek,
    .unlocked_ioctl = roccat_ioctl,
};

static int __init roccat_init(void)
{
    int retval;
    dev_t dev_id;

    retval = alloc_chrdev_region(&dev_id, ROCCAT_FIRST_MINOR,
            ROCCAT_MAX_DEVICES, "roccat");

    roccat_major = MAJOR(dev_id);

    if (retval < 0) {
        pr_warn("can't get major number\n");
        return retval;
    }

    cdev_init(&roccat_cdev, &roccat_ops);
    cdev_add(&roccat_cdev, dev_id, ROCCAT_MAX_DEVICES);

    return 0;
}

static void __exit roccat_exit(void)
{
    dev_t dev_id = MKDEV(roccat_major, 0);

    cdev_del(&roccat_cdev);
    unregister_chrdev_region(dev_id, ROCCAT_MAX_DEVICES);
}

module_init(roccat_init);
module_exit(roccat_exit);

MODULE_AUTHOR("Stefan Achatz");
MODULE_DESCRIPTION("USB Roccat char device");
MODULE_LICENSE("GPL v2");