/*
* userio kernel serio device emulation module
* Copyright (C) 2015 Red Hat
* Copyright (C) 2015 Stephen Chandler Paul <[email protected]>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
* General Public License for more details.
*/
#include <linux/circ_buf.h>
#include <linux/mutex.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/serio.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/sched.h>
#include <linux/poll.h>
#include <uapi/linux/userio.h>
#define USERIO_NAME "userio"
#define USERIO_BUFSIZE 16
static struct miscdevice userio_misc;
struct userio_device {
struct serio *serio;
struct mutex mutex;
bool running;
u8 head;
u8 tail;
spinlock_t buf_lock;
unsigned char buf[USERIO_BUFSIZE];
wait_queue_head_t waitq;
};
/**
* userio_device_write - Write data from serio to a userio device in userspace
* @id: The serio port for the userio device
* @val: The data to write to the device
*/
static int userio_device_write(struct serio *id, unsigned char val)
{
struct userio_device *userio = id->port_data;
unsigned long flags;
spin_lock_irqsave(&userio->buf_lock, flags);
userio->buf[userio->head] = val;
userio->head = (userio->head + 1) % USERIO_BUFSIZE;
if (userio->head == userio->tail)
dev_warn(userio_misc.this_device,
"Buffer overflowed, userio client isn't keeping up");
spin_unlock_irqrestore(&userio->buf_lock, flags);
wake_up_interruptible(&userio->waitq);
return 0;
}
static int userio_char_open(struct inode *inode, struct file *file)
{
struct userio_device *userio;
userio = kzalloc(sizeof(*userio), GFP_KERNEL);
if (!userio)
return -ENOMEM;
mutex_init(&userio->mutex);
spin_lock_init(&userio->buf_lock);
init_waitqueue_head(&userio->waitq);
userio->serio = kzalloc(sizeof(*userio->serio), GFP_KERNEL);
if (!userio->serio) {
kfree(userio);
return -ENOMEM;
}
userio->serio->write = userio_device_write;
userio->serio->port_data = userio;
file->private_data = userio;
return 0;
}
static int userio_char_release(struct inode *inode, struct file *file)
{
struct userio_device *userio = file->private_data;
if (userio->running) {
/*
* Don't free the serio port here, serio_unregister_port()
* does it for us.
*/
serio_unregister_port(userio->serio);
} else {
kfree(userio->serio);
}
kfree(userio);
return 0;
}
static ssize_t userio_char_read(struct file *file, char __user *user_buffer,
size_t count, loff_t *ppos)
{
struct userio_device *userio = file->private_data;
int error;
size_t nonwrap_len, copylen;
unsigned char buf[USERIO_BUFSIZE];
unsigned long flags;
/*
* By the time we get here, the data that was waiting might have
* been taken by another thread. Grab the buffer lock and check if
* there's still any data waiting, otherwise repeat this process
* until we have data (unless the file descriptor is non-blocking
* of course).
*/
for (;;) {
spin_lock_irqsave(&userio->buf_lock, flags);
nonwrap_len = CIRC_CNT_TO_END(userio->head,
userio->tail,
USERIO_BUFSIZE);
copylen = min(nonwrap_len, count);
if (copylen) {
memcpy(buf, &userio->buf[userio->tail], copylen);
userio->tail = (userio->tail + copylen) %
USERIO_BUFSIZE;
}
spin_unlock_irqrestore(&userio->buf_lock, flags);
if (nonwrap_len)
break;
/* buffer was/is empty */
if (file->f_flags & O_NONBLOCK)
return -EAGAIN;
/*
* count == 0 is special - no IO is done but we check
* for error conditions (see above).
*/
if (count == 0)
return 0;
error = wait_event_interruptible(userio->waitq,
userio->head != userio->tail);
if (error)
return error;
}
if (copylen)
if (copy_to_user(user_buffer, buf, copylen))
return -EFAULT;
return copylen;
}
static ssize_t userio_char_write(struct file *file, const char __user *buffer,
size_t count, loff_t *ppos)
{
struct userio_device *userio = file->private_data;
struct userio_cmd cmd;
int error;
if (count != sizeof(cmd)) {
dev_warn(userio_misc.this_device, "Invalid payload size\n");
return -EINVAL;
}
if (copy_from_user(&cmd, buffer, sizeof(cmd)))
return -EFAULT;
error = mutex_lock_interruptible(&userio->mutex);
if (error)
return error;
switch (cmd.type) {
case USERIO_CMD_REGISTER:
if (!userio->serio->id.type) {
dev_warn(userio_misc.this_device,
"No port type given on /dev/userio\n");
error = -EINVAL;
goto out;
}
if (userio->running) {
dev_warn(userio_misc.this_device,
"Begin command sent, but we're already running\n");
error = -EBUSY;
goto out;
}
userio->running = true;
serio_register_port(userio->serio);
break;
case USERIO_CMD_SET_PORT_TYPE:
if (userio->running) {
dev_warn(userio_misc.this_device,
"Can't change port type on an already running userio instance\n");
error = -EBUSY;
goto out;
}
userio->serio->id.type = cmd.data;
break;
case USERIO_CMD_SEND_INTERRUPT:
if (!userio->running) {
dev_warn(userio_misc.this_device,
"The device must be registered before sending interrupts\n");
error = -ENODEV;
goto out;
}
serio_interrupt(userio->serio, cmd.data, 0);
break;
default:
error = -EOPNOTSUPP;
goto out;
}
out:
mutex_unlock(&userio->mutex);
return error ?: count;
}
static __poll_t userio_char_poll(struct file *file, poll_table *wait)
{
struct userio_device *userio = file->private_data;
poll_wait(file, &userio->waitq, wait);
if (userio->head != userio->tail)
return EPOLLIN | EPOLLRDNORM;
return 0;
}
static const struct file_operations userio_fops = {
.owner = THIS_MODULE,
.open = userio_char_open,
.release = userio_char_release,
.read = userio_char_read,
.write = userio_char_write,
.poll = userio_char_poll,
};
static struct miscdevice userio_misc = {
.fops = &userio_fops,
.minor = USERIO_MINOR,
.name = USERIO_NAME,
};
module_driver(userio_misc, misc_register, misc_deregister);
MODULE_ALIAS_MISCDEV(USERIO_MINOR);
MODULE_ALIAS("devname:" USERIO_NAME);
MODULE_AUTHOR("Stephen Chandler Paul <[email protected]>");
MODULE_DESCRIPTION("Virtual Serio Device Support");
MODULE_LICENSE("GPL");
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