/*
 * Copyright (C) 2005 MIPS Technologies, Inc.  All rights reserved.
 *
 *  This program is free software; you can distribute it and/or modify it
 *  under the terms of the GNU General Public License (Version 2) as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope it will be useful, but WITHOUT
 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <asm/mipsmtregs.h>
#include <asm/bitops.h>
#include <asm/cpu.h>
#include <asm/processor.h>
#include <asm/rtlx.h>
#include <asm/uaccess.h>

#define RTLX_TARG_VPE 1

static struct rtlx_info *rtlx;
static int major;
static char module_name[] = "rtlx";
static struct irqaction irq;
static int irq_num;

static inline int spacefree(int read, int write, int size)
{
	if (read == write) {
		/*
		 * never fill the buffer completely, so indexes are always
		 * equal if empty and only empty, or !equal if data available
		 */
		return size - 1;
	}

	return ((read + size - write) % size) - 1;
}

static struct chan_waitqueues {
	wait_queue_head_t rt_queue;
	wait_queue_head_t lx_queue;
} channel_wqs[RTLX_CHANNELS];

extern void *vpe_get_shared(int index);

static void rtlx_dispatch(struct pt_regs *regs)
{
	do_IRQ(MIPSCPU_INT_BASE + MIPS_CPU_RTLX_IRQ, regs);
}

static irqreturn_t rtlx_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
	int i;

	for (i = 0; i < RTLX_CHANNELS; i++) {
		struct rtlx_channel *chan = &rtlx->channel[i];

		if (chan->lx_read != chan->lx_write)
			wake_up_interruptible(&channel_wqs[i].lx_queue);
	}

	return IRQ_HANDLED;
}

/* call when we have the address of the shared structure from the SP side. */
static int rtlx_init(struct rtlx_info *rtlxi)
{
	int i;

	if (rtlxi->id != RTLX_ID) {
		printk(KERN_WARNING "no valid RTLX id at 0x%p\n", rtlxi);
		return -ENOEXEC;
	}

	/* initialise the wait queues */
	for (i = 0; i < RTLX_CHANNELS; i++) {
		init_waitqueue_head(&channel_wqs[i].rt_queue);
		init_waitqueue_head(&channel_wqs[i].lx_queue);
	}

	/* set up for interrupt handling */
	memset(&irq, 0, sizeof(struct irqaction));

	if (cpu_has_vint)
		set_vi_handler(MIPS_CPU_RTLX_IRQ, rtlx_dispatch);

	irq_num = MIPSCPU_INT_BASE + MIPS_CPU_RTLX_IRQ;
	irq.handler = rtlx_interrupt;
	irq.flags = SA_INTERRUPT;
	irq.name = "RTLX";
	irq.dev_id = rtlx;
	setup_irq(irq_num, &irq);

	rtlx = rtlxi;

	return 0;
}

/* only allow one open process at a time to open each channel */
static int rtlx_open(struct inode *inode, struct file *filp)
{
	int minor, ret;
	struct rtlx_channel *chan;

	/* assume only 1 device at the mo. */
	minor = MINOR(inode->i_rdev);

	if (rtlx == NULL) {
		struct rtlx_info **p;
		if( (p = vpe_get_shared(RTLX_TARG_VPE)) == NULL) {
			printk(KERN_ERR "vpe_get_shared is NULL. "
			       "Has an SP program been loaded?\n");
			return -EFAULT;
		}

		if (*p == NULL) {
			printk(KERN_ERR "vpe_shared %p %p\n", p, *p);
			return -EFAULT;
		}

		if ((ret = rtlx_init(*p)) < 0)
			return ret;
	}

	chan = &rtlx->channel[minor];

	if (test_and_set_bit(RTLX_STATE_OPENED, &chan->lx_state))
		return -EBUSY;

	return 0;
}

static int rtlx_release(struct inode *inode, struct file *filp)
{
	int minor = MINOR(inode->i_rdev);

	clear_bit(RTLX_STATE_OPENED, &rtlx->channel[minor].lx_state);
	smp_mb__after_clear_bit();

	return 0;
}

static unsigned int rtlx_poll(struct file *file, poll_table * wait)
{
	int minor;
	unsigned int mask = 0;
	struct rtlx_channel *chan;

	minor = MINOR(file->f_dentry->d_inode->i_rdev);
	chan = &rtlx->channel[minor];

	poll_wait(file, &channel_wqs[minor].rt_queue, wait);
	poll_wait(file, &channel_wqs[minor].lx_queue, wait);

	/* data available to read? */
	if (chan->lx_read != chan->lx_write)
		mask |= POLLIN | POLLRDNORM;

	/* space to write */
	if (spacefree(chan->rt_read, chan->rt_write, chan->buffer_size))
		mask |= POLLOUT | POLLWRNORM;

	return mask;
}

static ssize_t rtlx_read(struct file *file, char __user * buffer, size_t count,
			 loff_t * ppos)
{
	unsigned long failed;
	size_t fl = 0L;
	int minor;
	struct rtlx_channel *lx;
	DECLARE_WAITQUEUE(wait, current);

	minor = MINOR(file->f_dentry->d_inode->i_rdev);
	lx = &rtlx->channel[minor];

	/* data available? */
	if (lx->lx_write == lx->lx_read) {
		if (file->f_flags & O_NONBLOCK)
			return 0;	/* -EAGAIN makes cat whinge */

		/* go to sleep */
		add_wait_queue(&channel_wqs[minor].lx_queue, &wait);
		set_current_state(TASK_INTERRUPTIBLE);

		while (lx->lx_write == lx->lx_read)
			schedule();

		set_current_state(TASK_RUNNING);
		remove_wait_queue(&channel_wqs[minor].lx_queue, &wait);

		/* back running */
	}

	/* find out how much in total */
	count = min(count,
		    (size_t)(lx->lx_write + lx->buffer_size - lx->lx_read) % lx->buffer_size);

	/* then how much from the read pointer onwards */
	fl = min(count, (size_t)lx->buffer_size - lx->lx_read);

	failed = copy_to_user (buffer, &lx->lx_buffer[lx->lx_read], fl);
	if (failed) {
		count = fl - failed;
		goto out;
	}

	/* and if there is anything left at the beginning of the buffer */
	if (count - fl) {
		failed = copy_to_user (buffer + fl, lx->lx_buffer, count - fl);
		if (failed) {
			count -= failed;
			goto out;
		}
	}

out:
	/* update the index */
	lx->lx_read += count;
	lx->lx_read %= lx->buffer_size;

	return count;
}

static ssize_t rtlx_write(struct file *file, const char __user * buffer,
			  size_t count, loff_t * ppos)
{
	unsigned long failed;
	int minor;
	struct rtlx_channel *rt;
	size_t fl;
	DECLARE_WAITQUEUE(wait, current);

	minor = MINOR(file->f_dentry->d_inode->i_rdev);
	rt = &rtlx->channel[minor];

	/* any space left... */
	if (!spacefree(rt->rt_read, rt->rt_write, rt->buffer_size)) {

		if (file->f_flags & O_NONBLOCK)
			return -EAGAIN;

		add_wait_queue(&channel_wqs[minor].rt_queue, &wait);
		set_current_state(TASK_INTERRUPTIBLE);

		while (!spacefree(rt->rt_read, rt->rt_write, rt->buffer_size))
			schedule();

		set_current_state(TASK_RUNNING);
		remove_wait_queue(&channel_wqs[minor].rt_queue, &wait);
	}

	/* total number of bytes to copy */
	count = min(count, (size_t)spacefree(rt->rt_read, rt->rt_write, rt->buffer_size) );

	/* first bit from write pointer to the end of the buffer, or count */
	fl = min(count, (size_t) rt->buffer_size - rt->rt_write);

	failed = copy_from_user(&rt->rt_buffer[rt->rt_write], buffer, fl);
	if (failed) {
		count = fl - failed;
		goto out;
	}

	/* if there's any left copy to the beginning of the buffer */
	if (count - fl) {
		failed = copy_from_user(rt->rt_buffer, buffer + fl, count - fl);
		if (failed) {
			count -= failed;
			goto out;
		}
	}

out:
	rt->rt_write += count;
	rt->rt_write %= rt->buffer_size;

	return count;
}

static struct file_operations rtlx_fops = {
	.owner		= THIS_MODULE,
	.open		= rtlx_open,
	.release	= rtlx_release,
	.write		= rtlx_write,
	.read		= rtlx_read,
	.poll		= rtlx_poll
};

static char register_chrdev_failed[] __initdata =
	KERN_ERR "rtlx_module_init: unable to register device\n";

static int __init rtlx_module_init(void)
{
	major = register_chrdev(0, module_name, &rtlx_fops);
	if (major < 0) {
		printk(register_chrdev_failed);
		return major;
	}

	return 0;
}

static void __exit rtlx_module_exit(void)
{
	unregister_chrdev(major, module_name);
}

module_init(rtlx_module_init);
module_exit(rtlx_module_exit);

MODULE_DESCRIPTION("MIPS RTLX");
MODULE_AUTHOR("Elizabeth Clarke, MIPS Technologies, Inc.");
MODULE_LICENSE("GPL");