mousedev.c

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/*
 * Input driver to ExplorerPS/2 device driver module.
 *
 * Copyright (c) 1999-2002 Vojtech Pavlik
 * Copyright (c) 2004      Dmitry Torokhov
 *
 * 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#define MOUSEDEV_MINOR_BASE 32
#define MOUSEDEV_MINORS     31
#define MOUSEDEV_MIX        63

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/input.h>
#include <linux/random.h>
#include <linux/major.h>
#include <linux/device.h>
#include <linux/cdev.h>
#include <linux/kernel.h>

MODULE_AUTHOR("Vojtech Pavlik <[email protected]>");
MODULE_DESCRIPTION("Mouse (ExplorerPS/2) device interfaces");
MODULE_LICENSE("GPL");

#ifndef CONFIG_INPUT_MOUSEDEV_SCREEN_X
#define CONFIG_INPUT_MOUSEDEV_SCREEN_X  1024
#endif
#ifndef CONFIG_INPUT_MOUSEDEV_SCREEN_Y
#define CONFIG_INPUT_MOUSEDEV_SCREEN_Y  768
#endif

static int xres = CONFIG_INPUT_MOUSEDEV_SCREEN_X;
module_param(xres, uint, 0644);
MODULE_PARM_DESC(xres, "Horizontal screen resolution");

static int yres = CONFIG_INPUT_MOUSEDEV_SCREEN_Y;
module_param(yres, uint, 0644);
MODULE_PARM_DESC(yres, "Vertical screen resolution");

static unsigned tap_time = 200;
module_param(tap_time, uint, 0644);
MODULE_PARM_DESC(tap_time, "Tap time for touchpads in absolute mode (msecs)");

struct mousedev_hw_data {
    int dx, dy, dz;
    int x, y;
    int abs_event;
    unsigned long buttons;
};

struct mousedev {
    int open;
    struct input_handle handle;
    wait_queue_head_t wait;
    struct list_head client_list;
    spinlock_t client_lock; /* protects client_list */
    struct mutex mutex;
    struct device dev;
    struct cdev cdev;
    bool exist;
    bool is_mixdev;

    struct list_head mixdev_node;
    bool opened_by_mixdev;

    struct mousedev_hw_data packet;
    unsigned int pkt_count;
    int old_x[4], old_y[4];
    int frac_dx, frac_dy;
    unsigned long touch;
};

enum mousedev_emul {
    MOUSEDEV_EMUL_PS2,
    MOUSEDEV_EMUL_IMPS,
    MOUSEDEV_EMUL_EXPS
};

struct mousedev_motion {
    int dx, dy, dz;
    unsigned long buttons;
};

#define PACKET_QUEUE_LEN    16
struct mousedev_client {
    struct fasync_struct *fasync;
    struct mousedev *mousedev;
    struct list_head node;

    struct mousedev_motion packets[PACKET_QUEUE_LEN];
    unsigned int head, tail;
    spinlock_t packet_lock;
    int pos_x, pos_y;

    signed char ps2[6];
    unsigned char ready, buffer, bufsiz;
    unsigned char imexseq, impsseq;
    enum mousedev_emul mode;
    unsigned long last_buttons;
};

#define MOUSEDEV_SEQ_LEN    6

static unsigned char mousedev_imps_seq[] = { 0xf3, 200, 0xf3, 100, 0xf3, 80 };
static unsigned char mousedev_imex_seq[] = { 0xf3, 200, 0xf3, 200, 0xf3, 80 };

static struct mousedev *mousedev_mix;
static LIST_HEAD(mousedev_mix_list);

static void mixdev_open_devices(void);
static void mixdev_close_devices(void);

#define fx(i)  (mousedev->old_x[(mousedev->pkt_count - (i)) & 03])
#define fy(i)  (mousedev->old_y[(mousedev->pkt_count - (i)) & 03])

static void mousedev_touchpad_event(struct input_dev *dev,
                    struct mousedev *mousedev,
                    unsigned int code, int value)
{
    int size, tmp;
    enum { FRACTION_DENOM = 128 };

    switch (code) {

    case ABS_X:

        fx(0) = value;
        if (mousedev->touch && mousedev->pkt_count >= 2) {
            size = input_abs_get_max(dev, ABS_X) -
                    input_abs_get_min(dev, ABS_X);
            if (size == 0)
                size = 256 * 2;

            tmp = ((value - fx(2)) * 256 * FRACTION_DENOM) / size;
            tmp += mousedev->frac_dx;
            mousedev->packet.dx = tmp / FRACTION_DENOM;
            mousedev->frac_dx =
                tmp - mousedev->packet.dx * FRACTION_DENOM;
        }
        break;

    case ABS_Y:
        fy(0) = value;
        if (mousedev->touch && mousedev->pkt_count >= 2) {
            /* use X size for ABS_Y to keep the same scale */
            size = input_abs_get_max(dev, ABS_X) -
                    input_abs_get_min(dev, ABS_X);
            if (size == 0)
                size = 256 * 2;

            tmp = -((value - fy(2)) * 256 * FRACTION_DENOM) / size;
            tmp += mousedev->frac_dy;
            mousedev->packet.dy = tmp / FRACTION_DENOM;
            mousedev->frac_dy = tmp -
                mousedev->packet.dy * FRACTION_DENOM;
        }
        break;
    }
}

static void mousedev_abs_event(struct input_dev *dev, struct mousedev *mousedev,
                unsigned int code, int value)
{
    int min, max, size;

    switch (code) {

    case ABS_X:
        min = input_abs_get_min(dev, ABS_X);
        max = input_abs_get_max(dev, ABS_X);

        size = max - min;
        if (size == 0)
            size = xres ? : 1;

        value = clamp(value, min, max);

        mousedev->packet.x = ((value - min) * xres) / size;
        mousedev->packet.abs_event = 1;
        break;

    case ABS_Y:
        min = input_abs_get_min(dev, ABS_Y);
        max = input_abs_get_max(dev, ABS_Y);

        size = max - min;
        if (size == 0)
            size = yres ? : 1;

        value = clamp(value, min, max);

        mousedev->packet.y = yres - ((value - min) * yres) / size;
        mousedev->packet.abs_event = 1;
        break;
    }
}

static void mousedev_rel_event(struct mousedev *mousedev,
                unsigned int code, int value)
{
    switch (code) {
    case REL_X:
        mousedev->packet.dx += value;
        break;

    case REL_Y:
        mousedev->packet.dy -= value;
        break;

    case REL_WHEEL:
        mousedev->packet.dz -= value;
        break;
    }
}

static void mousedev_key_event(struct mousedev *mousedev,
                unsigned int code, int value)
{
    int index;

    switch (code) {

    case BTN_TOUCH:
    case BTN_0:
    case BTN_LEFT:      index = 0; break;

    case BTN_STYLUS:
    case BTN_1:
    case BTN_RIGHT:     index = 1; break;

    case BTN_2:
    case BTN_FORWARD:
    case BTN_STYLUS2:
    case BTN_MIDDLE:    index = 2; break;

    case BTN_3:
    case BTN_BACK:
    case BTN_SIDE:      index = 3; break;

    case BTN_4:
    case BTN_EXTRA:     index = 4; break;

    default:        return;
    }

    if (value) {
        set_bit(index, &mousedev->packet.buttons);
        set_bit(index, &mousedev_mix->packet.buttons);
    } else {
        clear_bit(index, &mousedev->packet.buttons);
        clear_bit(index, &mousedev_mix->packet.buttons);
    }
}

static void mousedev_notify_readers(struct mousedev *mousedev,
                    struct mousedev_hw_data *packet)
{
    struct mousedev_client *client;
    struct mousedev_motion *p;
    unsigned int new_head;
    int wake_readers = 0;

    rcu_read_lock();
    list_for_each_entry_rcu(client, &mousedev->client_list, node) {

        /* Just acquire the lock, interrupts already disabled */
        spin_lock(&client->packet_lock);

        p = &client->packets[client->head];
        if (client->ready && p->buttons != mousedev->packet.buttons) {
            new_head = (client->head + 1) % PACKET_QUEUE_LEN;
            if (new_head != client->tail) {
                p = &client->packets[client->head = new_head];
                memset(p, 0, sizeof(struct mousedev_motion));
            }
        }

        if (packet->abs_event) {
            p->dx += packet->x - client->pos_x;
            p->dy += packet->y - client->pos_y;
            client->pos_x = packet->x;
            client->pos_y = packet->y;
        }

        client->pos_x += packet->dx;
        client->pos_x = client->pos_x < 0 ?
            0 : (client->pos_x >= xres ? xres : client->pos_x);
        client->pos_y += packet->dy;
        client->pos_y = client->pos_y < 0 ?
            0 : (client->pos_y >= yres ? yres : client->pos_y);

        p->dx += packet->dx;
        p->dy += packet->dy;
        p->dz += packet->dz;
        p->buttons = mousedev->packet.buttons;

        if (p->dx || p->dy || p->dz ||
            p->buttons != client->last_buttons)
            client->ready = 1;

        spin_unlock(&client->packet_lock);

        if (client->ready) {
            kill_fasync(&client->fasync, SIGIO, POLL_IN);
            wake_readers = 1;
        }
    }
    rcu_read_unlock();

    if (wake_readers)
        wake_up_interruptible(&mousedev->wait);
}

static void mousedev_touchpad_touch(struct mousedev *mousedev, int value)
{
    if (!value) {
        if (mousedev->touch &&
            time_before(jiffies,
                mousedev->touch + msecs_to_jiffies(tap_time))) {
            /*
             * Toggle left button to emulate tap.
             * We rely on the fact that mousedev_mix always has 0
             * motion packet so we won't mess current position.
             */
            set_bit(0, &mousedev->packet.buttons);
            set_bit(0, &mousedev_mix->packet.buttons);
            mousedev_notify_readers(mousedev, &mousedev_mix->packet);
            mousedev_notify_readers(mousedev_mix,
                        &mousedev_mix->packet);
            clear_bit(0, &mousedev->packet.buttons);
            clear_bit(0, &mousedev_mix->packet.buttons);
        }
        mousedev->touch = mousedev->pkt_count = 0;
        mousedev->frac_dx = 0;
        mousedev->frac_dy = 0;

    } else if (!mousedev->touch)
        mousedev->touch = jiffies;
}

static void mousedev_event(struct input_handle *handle,
               unsigned int type, unsigned int code, int value)
{
    struct mousedev *mousedev = handle->private;

    switch (type) {

    case EV_ABS:
        /* Ignore joysticks */
        if (test_bit(BTN_TRIGGER, handle->dev->keybit))
            return;

        if (test_bit(BTN_TOOL_FINGER, handle->dev->keybit))
            mousedev_touchpad_event(handle->dev,
                        mousedev, code, value);
        else
            mousedev_abs_event(handle->dev, mousedev, code, value);

        break;

    case EV_REL:
        mousedev_rel_event(mousedev, code, value);
        break;

    case EV_KEY:
        if (value != 2) {
            if (code == BTN_TOUCH &&
                test_bit(BTN_TOOL_FINGER, handle->dev->keybit))
                mousedev_touchpad_touch(mousedev, value);
            else
                mousedev_key_event(mousedev, code, value);
        }
        break;

    case EV_SYN:
        if (code == SYN_REPORT) {
            if (mousedev->touch) {
                mousedev->pkt_count++;
                /*
                 * Input system eats duplicate events,
                 * but we need all of them to do correct
                 * averaging so apply present one forward
                 */
                fx(0) = fx(1);
                fy(0) = fy(1);
            }

            mousedev_notify_readers(mousedev, &mousedev->packet);
            mousedev_notify_readers(mousedev_mix, &mousedev->packet);

            mousedev->packet.dx = mousedev->packet.dy =
                mousedev->packet.dz = 0;
            mousedev->packet.abs_event = 0;
        }
        break;
    }
}

static int mousedev_fasync(int fd, struct file *file, int on)
{
    struct mousedev_client *client = file->private_data;

    return fasync_helper(fd, file, on, &client->fasync);
}

static void mousedev_free(struct device *dev)
{
    struct mousedev *mousedev = container_of(dev, struct mousedev, dev);

    input_put_device(mousedev->handle.dev);
    kfree(mousedev);
}

static int mousedev_open_device(struct mousedev *mousedev)
{
    int retval;

    retval = mutex_lock_interruptible(&mousedev->mutex);
    if (retval)
        return retval;

    if (mousedev->is_mixdev)
        mixdev_open_devices();
    else if (!mousedev->exist)
        retval = -ENODEV;
    else if (!mousedev->open++) {
        retval = input_open_device(&mousedev->handle);
        if (retval)
            mousedev->open--;
    }

    mutex_unlock(&mousedev->mutex);
    return retval;
}

static void mousedev_close_device(struct mousedev *mousedev)
{
    mutex_lock(&mousedev->mutex);

    if (mousedev->is_mixdev)
        mixdev_close_devices();
    else if (mousedev->exist && !--mousedev->open)
        input_close_device(&mousedev->handle);

    mutex_unlock(&mousedev->mutex);
}

/*
 * Open all available devices so they can all be multiplexed in one.
 * stream. Note that this function is called with mousedev_mix->mutex
 * held.
 */
static void mixdev_open_devices(void)
{
    struct mousedev *mousedev;

    if (mousedev_mix->open++)
        return;

    list_for_each_entry(mousedev, &mousedev_mix_list, mixdev_node) {
        if (!mousedev->opened_by_mixdev) {
            if (mousedev_open_device(mousedev))
                continue;

            mousedev->opened_by_mixdev = true;
        }
    }
}

/*
 * Close all devices that were opened as part of multiplexed
 * device. Note that this function is called with mousedev_mix->mutex
 * held.
 */
static void mixdev_close_devices(void)
{
    struct mousedev *mousedev;

    if (--mousedev_mix->open)
        return;

    list_for_each_entry(mousedev, &mousedev_mix_list, mixdev_node) {
        if (mousedev->opened_by_mixdev) {
            mousedev->opened_by_mixdev = false;
            mousedev_close_device(mousedev);
        }
    }
}


static void mousedev_attach_client(struct mousedev *mousedev,
                   struct mousedev_client *client)
{
    spin_lock(&mousedev->client_lock);
    list_add_tail_rcu(&client->node, &mousedev->client_list);
    spin_unlock(&mousedev->client_lock);
}

static void mousedev_detach_client(struct mousedev *mousedev,
                   struct mousedev_client *client)
{
    spin_lock(&mousedev->client_lock);
    list_del_rcu(&client->node);
    spin_unlock(&mousedev->client_lock);
    synchronize_rcu();
}

static int mousedev_release(struct inode *inode, struct file *file)
{
    struct mousedev_client *client = file->private_data;
    struct mousedev *mousedev = client->mousedev;

    mousedev_detach_client(mousedev, client);
    kfree(client);

    mousedev_close_device(mousedev);

    return 0;
}

static int mousedev_open(struct inode *inode, struct file *file)
{
    struct mousedev_client *client;
    struct mousedev *mousedev;
    int error;

#ifdef CONFIG_INPUT_MOUSEDEV_PSAUX
    if (imajor(inode) == MISC_MAJOR)
        mousedev = mousedev_mix;
    else
#endif
        mousedev = container_of(inode->i_cdev, struct mousedev, cdev);

    client = kzalloc(sizeof(struct mousedev_client), GFP_KERNEL);
    if (!client)
        return -ENOMEM;

    spin_lock_init(&client->packet_lock);
    client->pos_x = xres / 2;
    client->pos_y = yres / 2;
    client->mousedev = mousedev;
    mousedev_attach_client(mousedev, client);

    error = mousedev_open_device(mousedev);
    if (error)
        goto err_free_client;

    file->private_data = client;
    nonseekable_open(inode, file);

    return 0;

 err_free_client:
    mousedev_detach_client(mousedev, client);
    kfree(client);
    return error;
}

static inline int mousedev_limit_delta(int delta, int limit)
{
    return delta > limit ? limit : (delta < -limit ? -limit : delta);
}

static void mousedev_packet(struct mousedev_client *client,
                signed char *ps2_data)
{
    struct mousedev_motion *p = &client->packets[client->tail];

    ps2_data[0] = 0x08 |
        ((p->dx < 0) << 4) | ((p->dy < 0) << 5) | (p->buttons & 0x07);
    ps2_data[1] = mousedev_limit_delta(p->dx, 127);
    ps2_data[2] = mousedev_limit_delta(p->dy, 127);
    p->dx -= ps2_data[1];
    p->dy -= ps2_data[2];

    switch (client->mode) {
    case MOUSEDEV_EMUL_EXPS:
        ps2_data[3] = mousedev_limit_delta(p->dz, 7);
        p->dz -= ps2_data[3];
        ps2_data[3] = (ps2_data[3] & 0x0f) | ((p->buttons & 0x18) << 1);
        client->bufsiz = 4;
        break;

    case MOUSEDEV_EMUL_IMPS:
        ps2_data[0] |=
            ((p->buttons & 0x10) >> 3) | ((p->buttons & 0x08) >> 1);
        ps2_data[3] = mousedev_limit_delta(p->dz, 127);
        p->dz -= ps2_data[3];
        client->bufsiz = 4;
        break;

    case MOUSEDEV_EMUL_PS2:
    default:
        ps2_data[0] |=
            ((p->buttons & 0x10) >> 3) | ((p->buttons & 0x08) >> 1);
        p->dz = 0;
        client->bufsiz = 3;
        break;
    }

    if (!p->dx && !p->dy && !p->dz) {
        if (client->tail == client->head) {
            client->ready = 0;
            client->last_buttons = p->buttons;
        } else
            client->tail = (client->tail + 1) % PACKET_QUEUE_LEN;
    }
}

static void mousedev_generate_response(struct mousedev_client *client,
                    int command)
{
    client->ps2[0] = 0xfa; /* ACK */

    switch (command) {

    case 0xeb: /* Poll */
        mousedev_packet(client, &client->ps2[1]);
        client->bufsiz++; /* account for leading ACK */
        break;

    case 0xf2: /* Get ID */
        switch (client->mode) {
        case MOUSEDEV_EMUL_PS2:
            client->ps2[1] = 0;
            break;
        case MOUSEDEV_EMUL_IMPS:
            client->ps2[1] = 3;
            break;
        case MOUSEDEV_EMUL_EXPS:
            client->ps2[1] = 4;
            break;
        }
        client->bufsiz = 2;
        break;

    case 0xe9: /* Get info */
        client->ps2[1] = 0x60; client->ps2[2] = 3; client->ps2[3] = 200;
        client->bufsiz = 4;
        break;

    case 0xff: /* Reset */
        client->impsseq = client->imexseq = 0;
        client->mode = MOUSEDEV_EMUL_PS2;
        client->ps2[1] = 0xaa; client->ps2[2] = 0x00;
        client->bufsiz = 3;
        break;

    default:
        client->bufsiz = 1;
        break;
    }
    client->buffer = client->bufsiz;
}

static ssize_t mousedev_write(struct file *file, const char __user *buffer,
                size_t count, loff_t *ppos)
{
    struct mousedev_client *client = file->private_data;
    unsigned char c;
    unsigned int i;

    for (i = 0; i < count; i++) {

        if (get_user(c, buffer + i))
            return -EFAULT;

        spin_lock_irq(&client->packet_lock);

        if (c == mousedev_imex_seq[client->imexseq]) {
            if (++client->imexseq == MOUSEDEV_SEQ_LEN) {
                client->imexseq = 0;
                client->mode = MOUSEDEV_EMUL_EXPS;
            }
        } else
            client->imexseq = 0;

        if (c == mousedev_imps_seq[client->impsseq]) {
            if (++client->impsseq == MOUSEDEV_SEQ_LEN) {
                client->impsseq = 0;
                client->mode = MOUSEDEV_EMUL_IMPS;
            }
        } else
            client->impsseq = 0;

        mousedev_generate_response(client, c);

        spin_unlock_irq(&client->packet_lock);
    }

    kill_fasync(&client->fasync, SIGIO, POLL_IN);
    wake_up_interruptible(&client->mousedev->wait);

    return count;
}

static ssize_t mousedev_read(struct file *file, char __user *buffer,
                 size_t count, loff_t *ppos)
{
    struct mousedev_client *client = file->private_data;
    struct mousedev *mousedev = client->mousedev;
    signed char data[sizeof(client->ps2)];
    int retval = 0;

    if (!client->ready && !client->buffer && mousedev->exist &&
        (file->f_flags & O_NONBLOCK))
        return -EAGAIN;

    retval = wait_event_interruptible(mousedev->wait,
            !mousedev->exist || client->ready || client->buffer);
    if (retval)
        return retval;

    if (!mousedev->exist)
        return -ENODEV;

    spin_lock_irq(&client->packet_lock);

    if (!client->buffer && client->ready) {
        mousedev_packet(client, client->ps2);
        client->buffer = client->bufsiz;
    }

    if (count > client->buffer)
        count = client->buffer;

    memcpy(data, client->ps2 + client->bufsiz - client->buffer, count);
    client->buffer -= count;

    spin_unlock_irq(&client->packet_lock);

    if (copy_to_user(buffer, data, count))
        return -EFAULT;

    return count;
}

/* No kernel lock - fine */
static unsigned int mousedev_poll(struct file *file, poll_table *wait)
{
    struct mousedev_client *client = file->private_data;
    struct mousedev *mousedev = client->mousedev;
    unsigned int mask;

    poll_wait(file, &mousedev->wait, wait);

    mask = mousedev->exist ? POLLOUT | POLLWRNORM : POLLHUP | POLLERR;
    if (client->ready || client->buffer)
        mask |= POLLIN | POLLRDNORM;

    return mask;
}

static const struct file_operations mousedev_fops = {
    .owner      = THIS_MODULE,
    .read       = mousedev_read,
    .write      = mousedev_write,
    .poll       = mousedev_poll,
    .open       = mousedev_open,
    .release    = mousedev_release,
    .fasync     = mousedev_fasync,
    .llseek     = noop_llseek,
};

/*
 * Mark device non-existent. This disables writes, ioctls and
 * prevents new users from opening the device. Already posted
 * blocking reads will stay, however new ones will fail.
 */
static void mousedev_mark_dead(struct mousedev *mousedev)
{
    mutex_lock(&mousedev->mutex);
    mousedev->exist = false;
    mutex_unlock(&mousedev->mutex);
}

/*
 * Wake up users waiting for IO so they can disconnect from
 * dead device.
 */
static void mousedev_hangup(struct mousedev *mousedev)
{
    struct mousedev_client *client;

    spin_lock(&mousedev->client_lock);
    list_for_each_entry(client, &mousedev->client_list, node)
        kill_fasync(&client->fasync, SIGIO, POLL_HUP);
    spin_unlock(&mousedev->client_lock);

    wake_up_interruptible(&mousedev->wait);
}

static void mousedev_cleanup(struct mousedev *mousedev)
{
    struct input_handle *handle = &mousedev->handle;

    mousedev_mark_dead(mousedev);
    mousedev_hangup(mousedev);

    cdev_del(&mousedev->cdev);

    /* mousedev is marked dead so no one else accesses mousedev->open */
    if (mousedev->open)
        input_close_device(handle);
}

static int mousedev_reserve_minor(bool mixdev)
{
    int minor;

    if (mixdev) {
        minor = input_get_new_minor(MOUSEDEV_MIX, 1, false);
        if (minor < 0)
            pr_err("failed to reserve mixdev minor: %d\n", minor);
    } else {
        minor = input_get_new_minor(MOUSEDEV_MINOR_BASE,
                        MOUSEDEV_MINORS, true);
        if (minor < 0)
            pr_err("failed to reserve new minor: %d\n", minor);
    }

    return minor;
}

static struct mousedev *mousedev_create(struct input_dev *dev,
                    struct input_handler *handler,
                    bool mixdev)
{
    struct mousedev *mousedev;
    int minor;
    int error;

    minor = mousedev_reserve_minor(mixdev);
    if (minor < 0) {
        error = minor;
        goto err_out;
    }

    mousedev = kzalloc(sizeof(struct mousedev), GFP_KERNEL);
    if (!mousedev) {
        error = -ENOMEM;
        goto err_free_minor;
    }

    INIT_LIST_HEAD(&mousedev->client_list);
    INIT_LIST_HEAD(&mousedev->mixdev_node);
    spin_lock_init(&mousedev->client_lock);
    mutex_init(&mousedev->mutex);
    lockdep_set_subclass(&mousedev->mutex,
                 mixdev ? SINGLE_DEPTH_NESTING : 0);
    init_waitqueue_head(&mousedev->wait);

    if (mixdev) {
        dev_set_name(&mousedev->dev, "mice");
    } else {
        int dev_no = minor;
        /* Normalize device number if it falls into legacy range */
        if (dev_no < MOUSEDEV_MINOR_BASE + MOUSEDEV_MINORS)
            dev_no -= MOUSEDEV_MINOR_BASE;
        dev_set_name(&mousedev->dev, "mouse%d", dev_no);
    }

    mousedev->exist = true;
    mousedev->is_mixdev = mixdev;
    mousedev->handle.dev = input_get_device(dev);
    mousedev->handle.name = dev_name(&mousedev->dev);
    mousedev->handle.handler = handler;
    mousedev->handle.private = mousedev;

    mousedev->dev.class = &input_class;
    if (dev)
        mousedev->dev.parent = &dev->dev;
    mousedev->dev.devt = MKDEV(INPUT_MAJOR, minor);
    mousedev->dev.release = mousedev_free;
    device_initialize(&mousedev->dev);

    if (!mixdev) {
        error = input_register_handle(&mousedev->handle);
        if (error)
            goto err_free_mousedev;
    }

    cdev_init(&mousedev->cdev, &mousedev_fops);
    mousedev->cdev.kobj.parent = &mousedev->dev.kobj;
    error = cdev_add(&mousedev->cdev, mousedev->dev.devt, 1);
    if (error)
        goto err_unregister_handle;

    error = device_add(&mousedev->dev);
    if (error)
        goto err_cleanup_mousedev;

    return mousedev;

 err_cleanup_mousedev:
    mousedev_cleanup(mousedev);
 err_unregister_handle:
    if (!mixdev)
        input_unregister_handle(&mousedev->handle);
 err_free_mousedev:
    put_device(&mousedev->dev);
 err_free_minor:
    input_free_minor(minor);
 err_out:
    return ERR_PTR(error);
}

static void mousedev_destroy(struct mousedev *mousedev)
{
    device_del(&mousedev->dev);
    mousedev_cleanup(mousedev);
    input_free_minor(MINOR(mousedev->dev.devt));
    if (!mousedev->is_mixdev)
        input_unregister_handle(&mousedev->handle);
    put_device(&mousedev->dev);
}

static int mixdev_add_device(struct mousedev *mousedev)
{
    int retval;

    retval = mutex_lock_interruptible(&mousedev_mix->mutex);
    if (retval)
        return retval;

    if (mousedev_mix->open) {
        retval = mousedev_open_device(mousedev);
        if (retval)
            goto out;

        mousedev->opened_by_mixdev = true;
    }

    get_device(&mousedev->dev);
    list_add_tail(&mousedev->mixdev_node, &mousedev_mix_list);

 out:
    mutex_unlock(&mousedev_mix->mutex);
    return retval;
}

static void mixdev_remove_device(struct mousedev *mousedev)
{
    mutex_lock(&mousedev_mix->mutex);

    if (mousedev->opened_by_mixdev) {
        mousedev->opened_by_mixdev = false;
        mousedev_close_device(mousedev);
    }

    list_del_init(&mousedev->mixdev_node);
    mutex_unlock(&mousedev_mix->mutex);

    put_device(&mousedev->dev);
}

static int mousedev_connect(struct input_handler *handler,
                struct input_dev *dev,
                const struct input_device_id *id)
{
    struct mousedev *mousedev;
    int error;

    mousedev = mousedev_create(dev, handler, false);
    if (IS_ERR(mousedev))
        return PTR_ERR(mousedev);

    error = mixdev_add_device(mousedev);
    if (error) {
        mousedev_destroy(mousedev);
        return error;
    }

    return 0;
}

static void mousedev_disconnect(struct input_handle *handle)
{
    struct mousedev *mousedev = handle->private;

    mixdev_remove_device(mousedev);
    mousedev_destroy(mousedev);
}

static const struct input_device_id mousedev_ids[] = {
    {
        .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
                INPUT_DEVICE_ID_MATCH_KEYBIT |
                INPUT_DEVICE_ID_MATCH_RELBIT,
        .evbit = { BIT_MASK(EV_KEY) | BIT_MASK(EV_REL) },
        .keybit = { [BIT_WORD(BTN_LEFT)] = BIT_MASK(BTN_LEFT) },
        .relbit = { BIT_MASK(REL_X) | BIT_MASK(REL_Y) },
    },  /* A mouse like device, at least one button,
           two relative axes */
    {
        .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
                INPUT_DEVICE_ID_MATCH_RELBIT,
        .evbit = { BIT_MASK(EV_KEY) | BIT_MASK(EV_REL) },
        .relbit = { BIT_MASK(REL_WHEEL) },
    },  /* A separate scrollwheel */
    {
        .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
                INPUT_DEVICE_ID_MATCH_KEYBIT |
                INPUT_DEVICE_ID_MATCH_ABSBIT,
        .evbit = { BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS) },
        .keybit = { [BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH) },
        .absbit = { BIT_MASK(ABS_X) | BIT_MASK(ABS_Y) },
    },  /* A tablet like device, at least touch detection,
           two absolute axes */
    {
        .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
                INPUT_DEVICE_ID_MATCH_KEYBIT |
                INPUT_DEVICE_ID_MATCH_ABSBIT,
        .evbit = { BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS) },
        .keybit = { [BIT_WORD(BTN_TOOL_FINGER)] =
                BIT_MASK(BTN_TOOL_FINGER) },
        .absbit = { BIT_MASK(ABS_X) | BIT_MASK(ABS_Y) |
                BIT_MASK(ABS_PRESSURE) |
                BIT_MASK(ABS_TOOL_WIDTH) },
    },  /* A touchpad */
    {
        .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
            INPUT_DEVICE_ID_MATCH_KEYBIT |
            INPUT_DEVICE_ID_MATCH_ABSBIT,
        .evbit = { BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS) },
        .keybit = { [BIT_WORD(BTN_LEFT)] = BIT_MASK(BTN_LEFT) },
        .absbit = { BIT_MASK(ABS_X) | BIT_MASK(ABS_Y) },
    },  /* Mouse-like device with absolute X and Y but ordinary
           clicks, like hp ILO2 High Performance mouse */

    { },    /* Terminating entry */
};

MODULE_DEVICE_TABLE(input, mousedev_ids);

static struct input_handler mousedev_handler = {
    .event      = mousedev_event,
    .connect    = mousedev_connect,
    .disconnect = mousedev_disconnect,
    .legacy_minors  = true,
    .minor      = MOUSEDEV_MINOR_BASE,
    .name       = "mousedev",
    .id_table   = mousedev_ids,
};

#ifdef CONFIG_INPUT_MOUSEDEV_PSAUX
#include <linux/miscdevice.h>

static struct miscdevice psaux_mouse = {
    .minor  = PSMOUSE_MINOR,
    .name   = "psaux",
    .fops   = &mousedev_fops,
};

static bool psaux_registered;

static void __init mousedev_psaux_register(void)
{
    int error;

    error = misc_register(&psaux_mouse);
    if (error)
        pr_warn("could not register psaux device, error: %d\n",
               error);
    else
        psaux_registered = true;
}

static void __exit mousedev_psaux_unregister(void)
{
    if (psaux_registered)
        misc_deregister(&psaux_mouse);
}
#else
static inline void mousedev_psaux_register(void) { }
static inline void mousedev_psaux_unregister(void) { }
#endif

static int __init mousedev_init(void)
{
    int error;

    mousedev_mix = mousedev_create(NULL, &mousedev_handler, true);
    if (IS_ERR(mousedev_mix))
        return PTR_ERR(mousedev_mix);

    error = input_register_handler(&mousedev_handler);
    if (error) {
        mousedev_destroy(mousedev_mix);
        return error;
    }

    mousedev_psaux_register();

    pr_info("PS/2 mouse device common for all mice\n");

    return 0;
}

static void __exit mousedev_exit(void)
{
    mousedev_psaux_unregister();
    input_unregister_handler(&mousedev_handler);
    mousedev_destroy(mousedev_mix);
}

module_init(mousedev_init);
module_exit(mousedev_exit);