arch/mips/kernel/rtlx.c - kernel/msm-4.9 - Gitiles

 /*
  * Copyright (C) 2005 MIPS Technologies, Inc.  All rights reserved.
  * Copyright (C) 2005, 06 Ralf Baechle (ralf@linux-mips.org)
  *
  *  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 <asm/uaccess.h>
 #include <linux/slab.h>
 #include <linux/list.h>
 #include <linux/vmalloc.h>
 #include <linux/elf.h>
 #include <linux/seq_file.h>
 #include <linux/syscalls.h>
 #include <linux/moduleloader.h>
 #include <linux/interrupt.h>
 #include <linux/poll.h>
 #include <linux/sched.h>
 #include <linux/wait.h>
 #include <asm/mipsmtregs.h>
 #include <asm/cacheflush.h>
 #include <asm/atomic.h>
 #include <asm/cpu.h>
 #include <asm/processor.h>
 #include <asm/system.h>
 #include <asm/vpe.h>
 #include <asm/rtlx.h>

 #define RTLX_TARG_VPE 1

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

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

 static struct irqaction irq;
 static int irq_num;
 static struct vpe_notifications notify;
 static int sp_stopping = 0;

 extern void *vpe_get_shared(int index);

 static void rtlx_dispatch(void)
 {
 	do_IRQ(MIPSCPU_INT_BASE + MIPS_CPU_RTLX_IRQ);
 }


 /* Interrupt handler may be called before rtlx_init has otherwise had
    a chance to run.
 */
 static irqreturn_t rtlx_interrupt(int irq, void *dev_id)
 {
 	int i;

 	for (i = 0; i < RTLX_CHANNELS; i++) {
 			wake_up(&channel_wqs[i].lx_queue);
 			wake_up(&channel_wqs[i].rt_queue);
 	}

 	return IRQ_HANDLED;
 }

 static __attribute_used__ void dump_rtlx(void)
 {
 	int i;

 	printk("id 0x%lx state %d\n", rtlx->id, rtlx->state);

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

 		printk(" rt_state %d lx_state %d buffer_size %d\n",
 		       chan->rt_state, chan->lx_state, chan->buffer_size);

 		printk(" rt_read %d rt_write %d\n",
 		       chan->rt_read, chan->rt_write);

 		printk(" lx_read %d lx_write %d\n",
 		       chan->lx_read, chan->lx_write);

 		printk(" rt_buffer <%s>\n", chan->rt_buffer);
 		printk(" lx_buffer <%s>\n", chan->lx_buffer);
 	}
 }

 /* call when we have the address of the shared structure from the SP side. */
 static int rtlx_init(struct rtlx_info *rtlxi)
 {
 	if (rtlxi->id != RTLX_ID) {
 		printk(KERN_ERR "no valid RTLX id at 0x%p 0x%x\n", rtlxi, rtlxi->id);
 		return -ENOEXEC;
 	}

 	rtlx = rtlxi;

 	return 0;
 }

 /* notifications */
 static void starting(int vpe)
 {
 	int i;
 	sp_stopping = 0;

 	/* force a reload of rtlx */
 	rtlx=NULL;

 	/* wake up any sleeping rtlx_open's */
 	for (i = 0; i < RTLX_CHANNELS; i++)
 		wake_up_interruptible(&channel_wqs[i].lx_queue);
 }

 static void stopping(int vpe)
 {
 	int i;

 	sp_stopping = 1;
 	for (i = 0; i < RTLX_CHANNELS; i++)
 		wake_up_interruptible(&channel_wqs[i].lx_queue);
 }


 int rtlx_open(int index, int can_sleep)
 {
 	int ret;
 	struct rtlx_channel *chan;
 	volatile struct rtlx_info **p;

 	if (index >= RTLX_CHANNELS) {
 		printk(KERN_DEBUG "rtlx_open index out of range\n");
 		return -ENOSYS;
 	}

 	if (channel_wqs[index].in_open) {
 		printk(KERN_DEBUG "rtlx_open channel %d already opened\n", index);
 		return -EBUSY;
 	}

 	channel_wqs[index].in_open++;

 	if (rtlx == NULL) {
 		if( (p = vpe_get_shared(RTLX_TARG_VPE)) == NULL) {
 			if (can_sleep) {
 				DECLARE_WAITQUEUE(wait, current);

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

 				set_current_state(TASK_INTERRUPTIBLE);
 				while ((p = vpe_get_shared(RTLX_TARG_VPE)) == NULL) {
 					schedule();
 					set_current_state(TASK_INTERRUPTIBLE);
 				}

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

 				/* back running */
 			} else {
 				printk( KERN_DEBUG "No SP program loaded, and device "
 					"opened with O_NONBLOCK\n");
 				channel_wqs[index].in_open = 0;
 				return -ENOSYS;
 			}
 		}

 		if (*p == NULL) {
 			if (can_sleep) {
 				DECLARE_WAITQUEUE(wait, current);

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

 				set_current_state(TASK_INTERRUPTIBLE);
 				while (*p == NULL) {
 					schedule();

 					/* reset task state to interruptable otherwise
 					   we'll whizz round here like a very fast loopy
 					   thing. schedule() appears to return with state
 					   set to TASK_RUNNING.

 					   If the loaded SP program, for whatever reason,
 					   doesn't set up the shared structure *p will never
 					   become true. So whoever connected to either /dev/rt?
 					   or if it was kspd, will then take up rather a lot of
 					   processor cycles.
 					*/

 					set_current_state(TASK_INTERRUPTIBLE);
 				}

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

 				/* back running */
 			}
 			else {
 				printk(" *vpe_get_shared is NULL. "
 				       "Has an SP program been loaded?\n");
 				channel_wqs[index].in_open = 0;
 				return -ENOSYS;
 			}
 		}

 		if ((unsigned int)*p < KSEG0) {
 			printk(KERN_WARNING "vpe_get_shared returned an invalid pointer "
 			       "maybe an error code %d\n", (int)*p);
  			channel_wqs[index].in_open = 0;
 			return -ENOSYS;
 		}

  		if ((ret = rtlx_init(*p)) < 0) {
  			channel_wqs[index].in_open = 0;
   			return ret;
  		}
 	}

 	chan = &rtlx->channel[index];

  	if (chan->lx_state == RTLX_STATE_OPENED) {
  		channel_wqs[index].in_open = 0;
   		return -EBUSY;
  	}

   	chan->lx_state = RTLX_STATE_OPENED;
  	channel_wqs[index].in_open = 0;
 	return 0;
 }

 int rtlx_release(int index)
 {
 	rtlx->channel[index].lx_state = RTLX_STATE_UNUSED;
 	return 0;
 }

 unsigned int rtlx_read_poll(int index, int can_sleep)
 {
  	struct rtlx_channel *chan;

  	if (rtlx == NULL)
  		return 0;

  	chan = &rtlx->channel[index];

 	/* data available to read? */
 	if (chan->lx_read == chan->lx_write) {
 		if (can_sleep) {
 			DECLARE_WAITQUEUE(wait, current);

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

 			set_current_state(TASK_INTERRUPTIBLE);
 			while (chan->lx_read == chan->lx_write) {
 				schedule();

 				set_current_state(TASK_INTERRUPTIBLE);

 				if (sp_stopping) {
 					set_current_state(TASK_RUNNING);
 					remove_wait_queue(&channel_wqs[index].lx_queue, &wait);
 					return 0;
 				}
 			}

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

 			/* back running */
 		}
 		else
 			return 0;
 	}

 	return (chan->lx_write + chan->buffer_size - chan->lx_read)
 	       % chan->buffer_size;
 }

 static inline int write_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;
 }

 unsigned int rtlx_write_poll(int index)
 {
 	struct rtlx_channel *chan = &rtlx->channel[index];
 	return write_spacefree(chan->rt_read, chan->rt_write, chan->buffer_size);
 }

 static inline void copy_to(void *dst, void *src, size_t count, int user)
 {
 	if (user)
 		copy_to_user(dst, src, count);
 	else
 		memcpy(dst, src, count);
 }

 static inline void copy_from(void *dst, void *src, size_t count, int user)
 {
 	if (user)
 		copy_from_user(dst, src, count);
 	else
 		memcpy(dst, src, count);
 }

 ssize_t rtlx_read(int index, void *buff, size_t count, int user)
 {
 	size_t fl = 0L;
 	struct rtlx_channel *lx;

 	if (rtlx == NULL)
 		return -ENOSYS;

 	lx = &rtlx->channel[index];

 	/* 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);

 	copy_to(buff, &lx->lx_buffer[lx->lx_read], fl, user);

 	/* and if there is anything left at the beginning of the buffer */
 	if ( count - fl )
 		copy_to (buff + fl, lx->lx_buffer, count - fl, user);

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

 	return count;
 }

 ssize_t rtlx_write(int index, void *buffer, size_t count, int user)
 {
 	struct rtlx_channel *rt;
 	size_t fl;

 	if (rtlx == NULL)
 		return(-ENOSYS);

 	rt = &rtlx->channel[index];

 	/* total number of bytes to copy */
 	count = min(count,
 		    (size_t)write_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);

 	copy_from (&rt->rt_buffer[rt->rt_write], buffer, fl, user);

 	/* if there's any left copy to the beginning of the buffer */
 	if( count - fl )
 		copy_from (rt->rt_buffer, buffer + fl, count - fl, user);

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

 	return(count);
 }


 static int file_open(struct inode *inode, struct file *filp)
 {
 	int minor = iminor(inode);

 	return rtlx_open(minor, (filp->f_flags & O_NONBLOCK) ? 0 : 1);
 }

 static int file_release(struct inode *inode, struct file *filp)
 {
 	int minor = iminor(inode);

 	return rtlx_release(minor);
 }

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

 	minor = iminor(file->f_path.dentry->d_inode);

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

 	if (rtlx == NULL)
 		return 0;

 	/* data available to read? */
 	if (rtlx_read_poll(minor, 0))
 		mask |= POLLIN | POLLRDNORM;

 	/* space to write */
 	if (rtlx_write_poll(minor))
 		mask |= POLLOUT | POLLWRNORM;

 	return mask;
 }

 static ssize_t file_read(struct file *file, char __user * buffer, size_t count,
 			 loff_t * ppos)
 {
 	int minor = iminor(file->f_path.dentry->d_inode);

 	/* data available? */
 	if (!rtlx_read_poll(minor, (file->f_flags & O_NONBLOCK) ? 0 : 1)) {
 		return 0;	// -EAGAIN makes cat whinge
 	}

 	return rtlx_read(minor, buffer, count, 1);
 }

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

 	minor = iminor(file->f_path.dentry->d_inode);
 	rt = &rtlx->channel[minor];

 	/* any space left... */
 	if (!rtlx_write_poll(minor)) {

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

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

 		while (!rtlx_write_poll(minor))
 			schedule();

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

 	return rtlx_write(minor, (void *)buffer, count, 1);
 }

 static struct file_operations rtlx_fops = {
 	.owner =   THIS_MODULE,
 	.open =    file_open,
 	.release = file_release,
 	.write =   file_write,
 	.read =    file_read,
 	.poll =    file_poll
 };

 static struct irqaction rtlx_irq = {
 	.handler	= rtlx_interrupt,
 	.flags		= IRQF_DISABLED,
 	.name		= "RTLX",
 };

 static int rtlx_irq_num = MIPSCPU_INT_BASE + MIPS_CPU_RTLX_IRQ;

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

 static int rtlx_module_init(void)
 {
 	int i;

 	major = register_chrdev(0, module_name, &rtlx_fops);
 	if (major < 0) {
 		printk(register_chrdev_failed);
 		return major;
 	}

 	/* 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);
 		channel_wqs[i].in_open = 0;
 	}

 	/* set up notifiers */
 	notify.start = starting;
 	notify.stop = stopping;
 	vpe_notify(RTLX_TARG_VPE, &notify);

 	if (cpu_has_vint)
 		set_vi_handler(MIPS_CPU_RTLX_IRQ, rtlx_dispatch);

 	rtlx_irq.dev_id = rtlx;
 	setup_irq(rtlx_irq_num, &rtlx_irq);

 	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 Oldham, MIPS Technologies, Inc.");
 MODULE_LICENSE("GPL");
	/*
	* Copyright (C) 2005 MIPS Technologies, Inc. All rights reserved.
	* Copyright (C) 2005, 06 Ralf Baechle (ralf@linux-mips.org)
	*
	* 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 <asm/uaccess.h>
	#include <linux/slab.h>
	#include <linux/list.h>
	#include <linux/vmalloc.h>
	#include <linux/elf.h>
	#include <linux/seq_file.h>
	#include <linux/syscalls.h>
	#include <linux/moduleloader.h>
	#include <linux/interrupt.h>
	#include <linux/poll.h>
	#include <linux/sched.h>
	#include <linux/wait.h>
	#include <asm/mipsmtregs.h>
	#include <asm/cacheflush.h>
	#include <asm/atomic.h>
	#include <asm/cpu.h>
	#include <asm/processor.h>
	#include <asm/system.h>
	#include <asm/vpe.h>
	#include <asm/rtlx.h>

	#define RTLX_TARG_VPE 1

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

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

	static struct irqaction irq;
	static int irq_num;
	static struct vpe_notifications notify;
	static int sp_stopping = 0;

	extern void *vpe_get_shared(int index);

	static void rtlx_dispatch(void)
	{
	do_IRQ(MIPSCPU_INT_BASE + MIPS_CPU_RTLX_IRQ);
	}


	/* Interrupt handler may be called before rtlx_init has otherwise had
	a chance to run.
	*/
	static irqreturn_t rtlx_interrupt(int irq, void *dev_id)
	{
	int i;

	for (i = 0; i < RTLX_CHANNELS; i++) {
	wake_up(&channel_wqs[i].lx_queue);
	wake_up(&channel_wqs[i].rt_queue);
	}

	return IRQ_HANDLED;
	}

	static __attribute_used__ void dump_rtlx(void)
	{
	int i;

	printk("id 0x%lx state %d\n", rtlx->id, rtlx->state);

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

	printk(" rt_state %d lx_state %d buffer_size %d\n",
	chan->rt_state, chan->lx_state, chan->buffer_size);

	printk(" rt_read %d rt_write %d\n",
	chan->rt_read, chan->rt_write);

	printk(" lx_read %d lx_write %d\n",
	chan->lx_read, chan->lx_write);

	printk(" rt_buffer <%s>\n", chan->rt_buffer);
	printk(" lx_buffer <%s>\n", chan->lx_buffer);
	}
	}

	/* call when we have the address of the shared structure from the SP side. */
	static int rtlx_init(struct rtlx_info *rtlxi)
	{
	if (rtlxi->id != RTLX_ID) {
	printk(KERN_ERR "no valid RTLX id at 0x%p 0x%x\n", rtlxi, rtlxi->id);
	return -ENOEXEC;
	}

	rtlx = rtlxi;

	return 0;
	}

	/* notifications */
	static void starting(int vpe)
	{
	int i;
	sp_stopping = 0;

	/* force a reload of rtlx */
	rtlx=NULL;

	/* wake up any sleeping rtlx_open's */
	for (i = 0; i < RTLX_CHANNELS; i++)
	wake_up_interruptible(&channel_wqs[i].lx_queue);
	}

	static void stopping(int vpe)
	{
	int i;

	sp_stopping = 1;
	for (i = 0; i < RTLX_CHANNELS; i++)
	wake_up_interruptible(&channel_wqs[i].lx_queue);
	}


	int rtlx_open(int index, int can_sleep)
	{
	int ret;
	struct rtlx_channel *chan;
	volatile struct rtlx_info **p;

	if (index >= RTLX_CHANNELS) {
	printk(KERN_DEBUG "rtlx_open index out of range\n");
	return -ENOSYS;
	}

	if (channel_wqs[index].in_open) {
	printk(KERN_DEBUG "rtlx_open channel %d already opened\n", index);
	return -EBUSY;
	}

	channel_wqs[index].in_open++;

	if (rtlx == NULL) {
	if( (p = vpe_get_shared(RTLX_TARG_VPE)) == NULL) {
	if (can_sleep) {
	DECLARE_WAITQUEUE(wait, current);

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

	set_current_state(TASK_INTERRUPTIBLE);
	while ((p = vpe_get_shared(RTLX_TARG_VPE)) == NULL) {
	schedule();
	set_current_state(TASK_INTERRUPTIBLE);
	}

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

	/* back running */
	} else {
	printk( KERN_DEBUG "No SP program loaded, and device "
	"opened with O_NONBLOCK\n");
	channel_wqs[index].in_open = 0;
	return -ENOSYS;
	}
	}

	if (*p == NULL) {
	if (can_sleep) {
	DECLARE_WAITQUEUE(wait, current);

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

	set_current_state(TASK_INTERRUPTIBLE);
	while (*p == NULL) {
	schedule();

	/* reset task state to interruptable otherwise
	we'll whizz round here like a very fast loopy
	thing. schedule() appears to return with state
	set to TASK_RUNNING.

	If the loaded SP program, for whatever reason,
	doesn't set up the shared structure *p will never
	become true. So whoever connected to either /dev/rt?
	or if it was kspd, will then take up rather a lot of
	processor cycles.
	*/

	set_current_state(TASK_INTERRUPTIBLE);
	}

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

	/* back running */
	}
	else {
	printk(" *vpe_get_shared is NULL. "
	"Has an SP program been loaded?\n");
	channel_wqs[index].in_open = 0;
	return -ENOSYS;
	}
	}

	if ((unsigned int)*p < KSEG0) {
	printk(KERN_WARNING "vpe_get_shared returned an invalid pointer "
	"maybe an error code %d\n", (int)*p);
	channel_wqs[index].in_open = 0;
	return -ENOSYS;
	}

	if ((ret = rtlx_init(*p)) < 0) {
	channel_wqs[index].in_open = 0;
	return ret;
	}
	}

	chan = &rtlx->channel[index];

	if (chan->lx_state == RTLX_STATE_OPENED) {
	channel_wqs[index].in_open = 0;
	return -EBUSY;
	}

	chan->lx_state = RTLX_STATE_OPENED;
	channel_wqs[index].in_open = 0;
	return 0;
	}

	int rtlx_release(int index)
	{
	rtlx->channel[index].lx_state = RTLX_STATE_UNUSED;
	return 0;
	}

	unsigned int rtlx_read_poll(int index, int can_sleep)
	{
	struct rtlx_channel *chan;

	if (rtlx == NULL)
	return 0;

	chan = &rtlx->channel[index];

	/* data available to read? */
	if (chan->lx_read == chan->lx_write) {
	if (can_sleep) {
	DECLARE_WAITQUEUE(wait, current);

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

	set_current_state(TASK_INTERRUPTIBLE);
	while (chan->lx_read == chan->lx_write) {
	schedule();

	set_current_state(TASK_INTERRUPTIBLE);

	if (sp_stopping) {
	set_current_state(TASK_RUNNING);
	remove_wait_queue(&channel_wqs[index].lx_queue, &wait);
	return 0;
	}
	}

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

	/* back running */
	}
	else
	return 0;
	}

	return (chan->lx_write + chan->buffer_size - chan->lx_read)
	% chan->buffer_size;
	}

	static inline int write_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;
	}

	unsigned int rtlx_write_poll(int index)
	{
	struct rtlx_channel *chan = &rtlx->channel[index];
	return write_spacefree(chan->rt_read, chan->rt_write, chan->buffer_size);
	}

	static inline void copy_to(void dst, void src, size_t count, int user)
	{
	if (user)
	copy_to_user(dst, src, count);
	else
	memcpy(dst, src, count);
	}

	static inline void copy_from(void dst, void src, size_t count, int user)
	{
	if (user)
	copy_from_user(dst, src, count);
	else
	memcpy(dst, src, count);
	}

	ssize_t rtlx_read(int index, void *buff, size_t count, int user)
	{
	size_t fl = 0L;
	struct rtlx_channel *lx;

	if (rtlx == NULL)
	return -ENOSYS;

	lx = &rtlx->channel[index];

	/* 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);

	copy_to(buff, &lx->lx_buffer[lx->lx_read], fl, user);

	/* and if there is anything left at the beginning of the buffer */
	if ( count - fl )
	copy_to (buff + fl, lx->lx_buffer, count - fl, user);

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

	return count;
	}

	ssize_t rtlx_write(int index, void *buffer, size_t count, int user)
	{
	struct rtlx_channel *rt;
	size_t fl;

	if (rtlx == NULL)
	return(-ENOSYS);

	rt = &rtlx->channel[index];

	/* total number of bytes to copy */
	count = min(count,
	(size_t)write_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);

	copy_from (&rt->rt_buffer[rt->rt_write], buffer, fl, user);

	/* if there's any left copy to the beginning of the buffer */
	if( count - fl )
	copy_from (rt->rt_buffer, buffer + fl, count - fl, user);

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

	return(count);
	}


	static int file_open(struct inode inode, struct file filp)
	{
	int minor = iminor(inode);

	return rtlx_open(minor, (filp->f_flags & O_NONBLOCK) ? 0 : 1);
	}

	static int file_release(struct inode inode, struct file filp)
	{
	int minor = iminor(inode);

	return rtlx_release(minor);
	}

	static unsigned int file_poll(struct file file, poll_table wait)
	{
	int minor;
	unsigned int mask = 0;

	minor = iminor(file->f_path.dentry->d_inode);

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

	if (rtlx == NULL)
	return 0;

	/* data available to read? */
	if (rtlx_read_poll(minor, 0))
	mask \|= POLLIN \| POLLRDNORM;

	/* space to write */
	if (rtlx_write_poll(minor))
	mask \|= POLLOUT \| POLLWRNORM;

	return mask;
	}

	static ssize_t file_read(struct file file, char __user buffer, size_t count,
	loff_t * ppos)
	{
	int minor = iminor(file->f_path.dentry->d_inode);

	/* data available? */
	if (!rtlx_read_poll(minor, (file->f_flags & O_NONBLOCK) ? 0 : 1)) {
	return 0; // -EAGAIN makes cat whinge
	}

	return rtlx_read(minor, buffer, count, 1);
	}

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

	minor = iminor(file->f_path.dentry->d_inode);
	rt = &rtlx->channel[minor];

	/* any space left... */
	if (!rtlx_write_poll(minor)) {

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

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

	while (!rtlx_write_poll(minor))
	schedule();

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

	return rtlx_write(minor, (void *)buffer, count, 1);
	}

	static struct file_operations rtlx_fops = {
	.owner = THIS_MODULE,
	.open = file_open,
	.release = file_release,
	.write = file_write,
	.read = file_read,
	.poll = file_poll
	};

	static struct irqaction rtlx_irq = {
	.handler = rtlx_interrupt,
	.flags = IRQF_DISABLED,
	.name = "RTLX",
	};

	static int rtlx_irq_num = MIPSCPU_INT_BASE + MIPS_CPU_RTLX_IRQ;

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

	static int rtlx_module_init(void)
	{
	int i;

	major = register_chrdev(0, module_name, &rtlx_fops);
	if (major < 0) {
	printk(register_chrdev_failed);
	return major;
	}

	/* 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);
	channel_wqs[i].in_open = 0;
	}

	/* set up notifiers */
	notify.start = starting;
	notify.stop = stopping;
	vpe_notify(RTLX_TARG_VPE, &notify);

	if (cpu_has_vint)
	set_vi_handler(MIPS_CPU_RTLX_IRQ, rtlx_dispatch);

	rtlx_irq.dev_id = rtlx;
	setup_irq(rtlx_irq_num, &rtlx_irq);

	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 Oldham, MIPS Technologies, Inc.");
	MODULE_LICENSE("GPL");