/*
 * 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 <vojtech@ucw.cz>");
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;

        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;

        int (*open_device)(struct mousedev *mousedev);
        void (*close_device)(struct mousedev *mousedev);
};

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);

#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->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->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 int mixdev_open_devices(struct mousedev *mixdev)
{
        int error;

        error = mutex_lock_interruptible(&mixdev->mutex);
        if (error)
                return error;

        if (!mixdev->open++) {
                struct mousedev *mousedev;

                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;
                        }
                }
        }

        mutex_unlock(&mixdev->mutex);
        return 0;
}

/*
 * 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(struct mousedev *mixdev)
{
        mutex_lock(&mixdev->mutex);

        if (!--mixdev->open) {
                struct mousedev *mousedev;

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

        mutex_unlock(&mixdev->mutex);
}


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);

        /* 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");

                mousedev->open_device = mixdev_open_devices;
                mousedev->close_device = mixdev_close_devices;
        } 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->open_device = mousedev_open_device;
                mousedev->close_device = mousedev_close_device;
        }

        mousedev->exist = true;
        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);

        error = cdev_device_add(&mousedev->cdev, &mousedev->dev);
        if (error)
                goto err_cleanup_mousedev;

        return mousedev;

 err_cleanup_mousedev:
        mousedev_cleanup(mousedev);
        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)
{
        cdev_device_del(&mousedev->cdev, &mousedev->dev);
        mousedev_cleanup(mousedev);
        input_free_minor(MINOR(mousedev->dev.devt));
        if (mousedev != mousedev_mix)
                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);