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/*
* User-space I/O driver support for HID subsystem
* Copyright (c) 2012 David Herrmann
*/
/*
* 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.
*/
#include <linux/atomic.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/hid.h>
#include <linux/input.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/uhid.h>
#include <linux/wait.h>
#define UHID_NAME "uhid"
#define UHID_BUFSIZE 32
struct uhid_device {
struct mutex devlock;
struct hid_device *hid;
wait_queue_head_t waitq;
spinlock_t qlock;
__u8 head;
__u8 tail;
struct uhid_event *outq[UHID_BUFSIZE];
};
static struct miscdevice uhid_misc;
static void uhid_queue(struct uhid_device *uhid, struct uhid_event *ev)
{
__u8 newhead;
newhead = (uhid->head + 1) % UHID_BUFSIZE;
if (newhead != uhid->tail) {
uhid->outq[uhid->head] = ev;
uhid->head = newhead;
wake_up_interruptible(&uhid->waitq);
} else {
hid_warn(uhid->hid, "Output queue is full\n");
kfree(ev);
}
}
static int uhid_queue_event(struct uhid_device *uhid, __u32 event)
{
unsigned long flags;
struct uhid_event *ev;
ev = kzalloc(sizeof(*ev), GFP_KERNEL);
if (!ev)
return -ENOMEM;
ev->type = event;
spin_lock_irqsave(&uhid->qlock, flags);
uhid_queue(uhid, ev);
spin_unlock_irqrestore(&uhid->qlock, flags);
return 0;
}
static int uhid_char_open(struct inode *inode, struct file *file)
{
struct uhid_device *uhid;
uhid = kzalloc(sizeof(*uhid), GFP_KERNEL);
if (!uhid)
return -ENOMEM;
mutex_init(&uhid->devlock);
spin_lock_init(&uhid->qlock);
init_waitqueue_head(&uhid->waitq);
file->private_data = uhid;
nonseekable_open(inode, file);
return 0;
}
static int uhid_char_release(struct inode *inode, struct file *file)
{
struct uhid_device *uhid = file->private_data;
unsigned int i;
for (i = 0; i < UHID_BUFSIZE; ++i)
kfree(uhid->outq[i]);
kfree(uhid);
return 0;
}
static ssize_t uhid_char_read(struct file *file, char __user *buffer,
size_t count, loff_t *ppos)
{
struct uhid_device *uhid = file->private_data;
int ret;
unsigned long flags;
size_t len;
/* they need at least the "type" member of uhid_event */
if (count < sizeof(__u32))
return -EINVAL;
try_again:
if (file->f_flags & O_NONBLOCK) {
if (uhid->head == uhid->tail)
return -EAGAIN;
} else {
ret = wait_event_interruptible(uhid->waitq,
uhid->head != uhid->tail);
if (ret)
return ret;
}
ret = mutex_lock_interruptible(&uhid->devlock);
if (ret)
return ret;
if (uhid->head == uhid->tail) {
mutex_unlock(&uhid->devlock);
goto try_again;
} else {
len = min(count, sizeof(**uhid->outq));
if (copy_to_user(buffer, &uhid->outq[uhid->tail], len)) {
ret = -EFAULT;
} else {
kfree(uhid->outq[uhid->tail]);
uhid->outq[uhid->tail] = NULL;
spin_lock_irqsave(&uhid->qlock, flags);
uhid->tail = (uhid->tail + 1) % UHID_BUFSIZE;
spin_unlock_irqrestore(&uhid->qlock, flags);
}
}
mutex_unlock(&uhid->devlock);
return ret ? ret : len;
}
static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
size_t count, loff_t *ppos)
{
return 0;
}
static unsigned int uhid_char_poll(struct file *file, poll_table *wait)
{
struct uhid_device *uhid = file->private_data;
poll_wait(file, &uhid->waitq, wait);
if (uhid->head != uhid->tail)
return POLLIN | POLLRDNORM;
return 0;
}
static const struct file_operations uhid_fops = {
.owner = THIS_MODULE,
.open = uhid_char_open,
.release = uhid_char_release,
.read = uhid_char_read,
.write = uhid_char_write,
.poll = uhid_char_poll,
.llseek = no_llseek,
};
static struct miscdevice uhid_misc = {
.fops = &uhid_fops,
.minor = MISC_DYNAMIC_MINOR,
.name = UHID_NAME,
};
static int __init uhid_init(void)
{
return misc_register(&uhid_misc);
}
static void __exit uhid_exit(void)
{
misc_deregister(&uhid_misc);
}
module_init(uhid_init);
module_exit(uhid_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("David Herrmann <dh.herrmann@gmail.com>");
MODULE_DESCRIPTION("User-space I/O driver support for HID subsystem");
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