serio_raw.c

Go to the documentation of this file.

/*
 * Raw serio device providing access to a raw byte stream from underlying
 * serio port. Closely emulates behavior of pre-2.6 /dev/psaux device
 *
 * 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.
 */

#include <linux/kref.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/module.h>
#include <linux/serio.h>
#include <linux/init.h>
#include <linux/major.h>
#include <linux/device.h>
#include <linux/miscdevice.h>
#include <linux/wait.h>
#include <linux/mutex.h>

#define DRIVER_DESC "Raw serio driver"

MODULE_AUTHOR("Dmitry Torokhov <[email protected]>");
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");

#define SERIO_RAW_QUEUE_LEN 64
struct serio_raw {
    unsigned char queue[SERIO_RAW_QUEUE_LEN];
    unsigned int tail, head;

    char name[16];
    struct kref kref;
    struct serio *serio;
    struct miscdevice dev;
    wait_queue_head_t wait;
    struct list_head client_list;
    struct list_head node;
    bool dead;
};

struct serio_raw_client {
    struct fasync_struct *fasync;
    struct serio_raw *serio_raw;
    struct list_head node;
};

static DEFINE_MUTEX(serio_raw_mutex);
static LIST_HEAD(serio_raw_list);

/*********************************************************************
 *             Interface with userspace (file operations)            *
 *********************************************************************/

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

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

static struct serio_raw *serio_raw_locate(int minor)
{
    struct serio_raw *serio_raw;

    list_for_each_entry(serio_raw, &serio_raw_list, node) {
        if (serio_raw->dev.minor == minor)
            return serio_raw;
    }

    return NULL;
}

static int serio_raw_open(struct inode *inode, struct file *file)
{
    struct serio_raw *serio_raw;
    struct serio_raw_client *client;
    int retval;

    retval = mutex_lock_interruptible(&serio_raw_mutex);
    if (retval)
        return retval;

    serio_raw = serio_raw_locate(iminor(inode));
    if (!serio_raw) {
        retval = -ENODEV;
        goto out;
    }

    if (serio_raw->dead) {
        retval = -ENODEV;
        goto out;
    }

    client = kzalloc(sizeof(struct serio_raw_client), GFP_KERNEL);
    if (!client) {
        retval = -ENOMEM;
        goto out;
    }

    client->serio_raw = serio_raw;
    file->private_data = client;

    kref_get(&serio_raw->kref);

    serio_pause_rx(serio_raw->serio);
    list_add_tail(&client->node, &serio_raw->client_list);
    serio_continue_rx(serio_raw->serio);

out:
    mutex_unlock(&serio_raw_mutex);
    return retval;
}

static void serio_raw_free(struct kref *kref)
{
    struct serio_raw *serio_raw =
            container_of(kref, struct serio_raw, kref);

    put_device(&serio_raw->serio->dev);
    kfree(serio_raw);
}

static int serio_raw_release(struct inode *inode, struct file *file)
{
    struct serio_raw_client *client = file->private_data;
    struct serio_raw *serio_raw = client->serio_raw;

    serio_pause_rx(serio_raw->serio);
    list_del(&client->node);
    serio_continue_rx(serio_raw->serio);

    kfree(client);

    kref_put(&serio_raw->kref, serio_raw_free);

    return 0;
}

static bool serio_raw_fetch_byte(struct serio_raw *serio_raw, char *c)
{
    bool empty;

    serio_pause_rx(serio_raw->serio);

    empty = serio_raw->head == serio_raw->tail;
    if (!empty) {
        *c = serio_raw->queue[serio_raw->tail];
        serio_raw->tail = (serio_raw->tail + 1) % SERIO_RAW_QUEUE_LEN;
    }

    serio_continue_rx(serio_raw->serio);

    return !empty;
}

static ssize_t serio_raw_read(struct file *file, char __user *buffer,
                  size_t count, loff_t *ppos)
{
    struct serio_raw_client *client = file->private_data;
    struct serio_raw *serio_raw = client->serio_raw;
    char uninitialized_var(c);
    ssize_t read = 0;
    int error;

    for (;;) {
        if (serio_raw->dead)
            return -ENODEV;

        if (serio_raw->head == serio_raw->tail &&
            (file->f_flags & O_NONBLOCK))
            return -EAGAIN;

        if (count == 0)
            break;

        while (read < count && serio_raw_fetch_byte(serio_raw, &c)) {
            if (put_user(c, buffer++))
                return -EFAULT;
            read++;
        }

        if (read)
            break;

        if (!(file->f_flags & O_NONBLOCK)) {
            error = wait_event_interruptible(serio_raw->wait,
                    serio_raw->head != serio_raw->tail ||
                    serio_raw->dead);
            if (error)
                return error;
        }
    }

    return read;
}

static ssize_t serio_raw_write(struct file *file, const char __user *buffer,
                   size_t count, loff_t *ppos)
{
    struct serio_raw_client *client = file->private_data;
    struct serio_raw *serio_raw = client->serio_raw;
    int retval = 0;
    unsigned char c;

    retval = mutex_lock_interruptible(&serio_raw_mutex);
    if (retval)
        return retval;

    if (serio_raw->dead) {
        retval = -ENODEV;
        goto out;
    }

    if (count > 32)
        count = 32;

    while (count--) {
        if (get_user(c, buffer++)) {
            retval = -EFAULT;
            goto out;
        }

        if (serio_write(serio_raw->serio, c)) {
            /* Either signal error or partial write */
            if (retval == 0)
                retval = -EIO;
            goto out;
        }

        retval++;
    }

out:
    mutex_unlock(&serio_raw_mutex);
    return retval;
}

static unsigned int serio_raw_poll(struct file *file, poll_table *wait)
{
    struct serio_raw_client *client = file->private_data;
    struct serio_raw *serio_raw = client->serio_raw;
    unsigned int mask;

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

    mask = serio_raw->dead ? POLLHUP | POLLERR : POLLOUT | POLLWRNORM;
    if (serio_raw->head != serio_raw->tail)
        mask |= POLLIN | POLLRDNORM;

    return mask;
}

static const struct file_operations serio_raw_fops = {
    .owner      = THIS_MODULE,
    .open       = serio_raw_open,
    .release    = serio_raw_release,
    .read       = serio_raw_read,
    .write      = serio_raw_write,
    .poll       = serio_raw_poll,
    .fasync     = serio_raw_fasync,
    .llseek     = noop_llseek,
};


/*********************************************************************
 *                   Interface with serio port                       *
 *********************************************************************/

static irqreturn_t serio_raw_interrupt(struct serio *serio, unsigned char data,
                    unsigned int dfl)
{
    struct serio_raw *serio_raw = serio_get_drvdata(serio);
    struct serio_raw_client *client;
    unsigned int head = serio_raw->head;

    /* we are holding serio->lock here so we are protected */
    serio_raw->queue[head] = data;
    head = (head + 1) % SERIO_RAW_QUEUE_LEN;
    if (likely(head != serio_raw->tail)) {
        serio_raw->head = head;
        list_for_each_entry(client, &serio_raw->client_list, node)
            kill_fasync(&client->fasync, SIGIO, POLL_IN);
        wake_up_interruptible(&serio_raw->wait);
    }

    return IRQ_HANDLED;
}

static int serio_raw_connect(struct serio *serio, struct serio_driver *drv)
{
    static atomic_t serio_raw_no = ATOMIC_INIT(0);
    struct serio_raw *serio_raw;
    int err;

    serio_raw = kzalloc(sizeof(struct serio_raw), GFP_KERNEL);
    if (!serio_raw) {
        dev_dbg(&serio->dev, "can't allocate memory for a device\n");
        return -ENOMEM;
    }

    snprintf(serio_raw->name, sizeof(serio_raw->name),
         "serio_raw%ld", (long)atomic_inc_return(&serio_raw_no) - 1);
    kref_init(&serio_raw->kref);
    INIT_LIST_HEAD(&serio_raw->client_list);
    init_waitqueue_head(&serio_raw->wait);

    serio_raw->serio = serio;
    get_device(&serio->dev);

    serio_set_drvdata(serio, serio_raw);

    err = serio_open(serio, drv);
    if (err)
        goto err_free;

    err = mutex_lock_killable(&serio_raw_mutex);
    if (err)
        goto err_close;

    list_add_tail(&serio_raw->node, &serio_raw_list);
    mutex_unlock(&serio_raw_mutex);

    serio_raw->dev.minor = PSMOUSE_MINOR;
    serio_raw->dev.name = serio_raw->name;
    serio_raw->dev.parent = &serio->dev;
    serio_raw->dev.fops = &serio_raw_fops;

    err = misc_register(&serio_raw->dev);
    if (err) {
        serio_raw->dev.minor = MISC_DYNAMIC_MINOR;
        err = misc_register(&serio_raw->dev);
    }

    if (err) {
        dev_err(&serio->dev,
            "failed to register raw access device for %s\n",
            serio->phys);
        goto err_unlink;
    }

    dev_info(&serio->dev, "raw access enabled on %s (%s, minor %d)\n",
         serio->phys, serio_raw->name, serio_raw->dev.minor);
    return 0;

err_unlink:
    list_del_init(&serio_raw->node);
err_close:
    serio_close(serio);
err_free:
    serio_set_drvdata(serio, NULL);
    kref_put(&serio_raw->kref, serio_raw_free);
    return err;
}

static int serio_raw_reconnect(struct serio *serio)
{
    struct serio_raw *serio_raw = serio_get_drvdata(serio);
    struct serio_driver *drv = serio->drv;

    if (!drv || !serio_raw) {
        dev_dbg(&serio->dev,
            "reconnect request, but serio is disconnected, ignoring...\n");
        return -1;
    }

    /*
     * Nothing needs to be done here, we just need this method to
     * keep the same device.
     */
    return 0;
}

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

    serio_pause_rx(serio_raw->serio);
    list_for_each_entry(client, &serio_raw->client_list, node)
        kill_fasync(&client->fasync, SIGIO, POLL_HUP);
    serio_continue_rx(serio_raw->serio);

    wake_up_interruptible(&serio_raw->wait);
}


static void serio_raw_disconnect(struct serio *serio)
{
    struct serio_raw *serio_raw = serio_get_drvdata(serio);

    misc_deregister(&serio_raw->dev);

    mutex_lock(&serio_raw_mutex);
    serio_raw->dead = true;
    list_del_init(&serio_raw->node);
    mutex_unlock(&serio_raw_mutex);

    serio_raw_hangup(serio_raw);

    serio_close(serio);
    kref_put(&serio_raw->kref, serio_raw_free);

    serio_set_drvdata(serio, NULL);
}

static struct serio_device_id serio_raw_serio_ids[] = {
    {
        .type   = SERIO_8042,
        .proto  = SERIO_ANY,
        .id = SERIO_ANY,
        .extra  = SERIO_ANY,
    },
    {
        .type   = SERIO_8042_XL,
        .proto  = SERIO_ANY,
        .id = SERIO_ANY,
        .extra  = SERIO_ANY,
    },
    { 0 }
};

MODULE_DEVICE_TABLE(serio, serio_raw_serio_ids);

static struct serio_driver serio_raw_drv = {
    .driver     = {
        .name   = "serio_raw",
    },
    .description    = DRIVER_DESC,
    .id_table   = serio_raw_serio_ids,
    .interrupt  = serio_raw_interrupt,
    .connect    = serio_raw_connect,
    .reconnect  = serio_raw_reconnect,
    .disconnect = serio_raw_disconnect,
    .manual_bind    = true,
};

module_serio_driver(serio_raw_drv);