short.c

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/*
 * short.c -- Simple Hardware Operations and Raw Tests
 * short.c -- also a brief example of interrupt handling ("short int")
 *
 * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet
 * Copyright (C) 2001 O'Reilly & Associates
 *
 * The source code in this file can be freely used, adapted,
 * and redistributed in source or binary form, so long as an
 * acknowledgment appears in derived source files.  The citation
 * should list that the code comes from the book "Linux Device
 * Drivers" by Alessandro Rubini and Jonathan Corbet, published
 * by O'Reilly & Associates.   No warranty is attached;
 * we cannot take responsibility for errors or fitness for use.
 *
 * $Id: short.c,v 1.16 2004/10/29 16:45:40 corbet Exp $
 */

/*
 * FIXME: this driver is not safe with concurrent readers or
 * writers.
 */

#include <linux/config.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>

#include <linux/sched.h>
#include <linux/kernel.h>	/* printk() */
#include <linux/fs.h>		/* everything... */
#include <linux/errno.h>	/* error codes */
#include <linux/delay.h>	/* udelay */
#include <linux/kdev_t.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/workqueue.h>
#include <linux/poll.h>
#include <linux/wait.h>

#include <asm/io.h>

#define SHORT_NR_PORTS	8	/* use 8 ports by default */

/*
 * all of the parameters have no "short_" prefix, to save typing when
 * specifying them at load time
 */
static int major = 0;	/* dynamic by default */
module_param(major, int, 0);

static int use_mem = 0;	/* default is I/O-mapped */
module_param(use_mem, int, 0);

/* default is the first printer port on PC's. "short_base" is there too
   because it's what we want to use in the code */
static unsigned long base = 0x378;
unsigned long short_base = 0;
module_param(base, long, 0);

/* The interrupt line is undefined by default. "short_irq" is as above */
static int irq = -1;
volatile int short_irq = -1;
module_param(irq, int, 0);

static int probe = 0;	/* select at load time how to probe irq line */
module_param(probe, int, 0);

static int wq = 0;	/* select at load time whether a workqueue is used */
module_param(wq, int, 0);

static int tasklet = 0;	/* select whether a tasklet is used */
module_param(tasklet, int, 0);

static int share = 0;	/* select at load time whether install a shared irq */
module_param(share, int, 0);

MODULE_AUTHOR ("Alessandro Rubini");
MODULE_LICENSE("Dual BSD/GPL");


unsigned long short_buffer = 0;
unsigned long volatile short_head;
volatile unsigned long short_tail;
DECLARE_WAIT_QUEUE_HEAD(short_queue);

/* Set up our tasklet if we're doing that. */
void short_do_tasklet(unsigned long);
DECLARE_TASKLET(short_tasklet, short_do_tasklet, 0);

/*
 * Atomicly increment an index into short_buffer
 */
static inline void short_incr_bp(volatile unsigned long *index, int delta)
{
	unsigned long new = *index + delta;
	barrier();  /* Don't optimize these two together */
	*index = (new >= (short_buffer + PAGE_SIZE)) ? short_buffer : new;
}


/*
 * The devices with low minor numbers write/read burst of data to/from
 * specific I/O ports (by default the parallel ones).
 * 
 * The device with 128 as minor number returns ascii strings telling
 * when interrupts have been received. Writing to the device toggles
 * 00/FF on the parallel data lines. If there is a loopback wire, this
 * generates interrupts.  
 */

int short_open (struct inode *inode, struct file *filp)
{
	extern struct file_operations short_i_fops;

	if (iminor (inode) & 0x80)
		filp->f_op = &short_i_fops; /* the interrupt-driven node */
	return 0;
}


int short_release (struct inode *inode, struct file *filp)
{
	return 0;
}


/* first, the port-oriented device */

enum short_modes {SHORT_DEFAULT=0, SHORT_PAUSE, SHORT_STRING, SHORT_MEMORY};

ssize_t do_short_read (struct inode *inode, struct file *filp, char __user *buf,
		size_t count, loff_t *f_pos)
{
	int retval = count, minor = iminor (inode);
	unsigned long port = short_base + (minor&0x0f);
	void *address = (void *) short_base + (minor&0x0f);
	int mode = (minor&0x70) >> 4;
	unsigned char *kbuf = kmalloc(count, GFP_KERNEL), *ptr;
    
	if (!kbuf)
		return -ENOMEM;
	ptr = kbuf;

	if (use_mem)
		mode = SHORT_MEMORY;
	
	switch(mode) {
	    case SHORT_STRING:
		insb(port, ptr, count);
		rmb();
		break;

	    case SHORT_DEFAULT:
		while (count--) {
			*(ptr++) = inb(port);
			rmb();
		}
		break;

	    case SHORT_MEMORY:
		while (count--) {
			*ptr++ = ioread8(address);
			rmb();
		}
		break;
	    case SHORT_PAUSE:
		while (count--) {
			*(ptr++) = inb_p(port);
			rmb();
		}
		break;

	    default: /* no more modes defined by now */
		retval = -EINVAL;
		break;
	}
	if ((retval > 0) && copy_to_user(buf, kbuf, retval))
		retval = -EFAULT;
	kfree(kbuf);
	return retval;
}


/*
 * Version-specific methods for the fops structure.  FIXME don't need anymore.
 */
ssize_t short_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
{
	return do_short_read(filp->f_dentry->d_inode, filp, buf, count, f_pos);
}



ssize_t do_short_write (struct inode *inode, struct file *filp, const char __user *buf,
		size_t count, loff_t *f_pos)
{
	int retval = count, minor = iminor(inode);
	unsigned long port = short_base + (minor&0x0f);
	void *address = (void *) short_base + (minor&0x0f);
	int mode = (minor&0x70) >> 4;
	unsigned char *kbuf = kmalloc(count, GFP_KERNEL), *ptr;

	if (!kbuf)
		return -ENOMEM;
	if (copy_from_user(kbuf, buf, count))
		return -EFAULT;
	ptr = kbuf;

	if (use_mem)
		mode = SHORT_MEMORY;

	switch(mode) {
	case SHORT_PAUSE:
		while (count--) {
			outb_p(*(ptr++), port);
			wmb();
		}
		break;

	case SHORT_STRING:
		outsb(port, ptr, count);
		wmb();
		break;

	case SHORT_DEFAULT:
		while (count--) {
			outb(*(ptr++), port);
			wmb();
		}
		break;

	case SHORT_MEMORY:
		while (count--) {
			iowrite8(*ptr++, address);
			wmb();
		}
		break;

	default: /* no more modes defined by now */
		retval = -EINVAL;
		break;
	}
	kfree(kbuf);
	return retval;
}


ssize_t short_write(struct file *filp, const char __user *buf, size_t count,
		loff_t *f_pos)
{
	return do_short_write(filp->f_dentry->d_inode, filp, buf, count, f_pos);
}




unsigned int short_poll(struct file *filp, poll_table *wait)
{
	return POLLIN | POLLRDNORM | POLLOUT | POLLWRNORM;
}






struct file_operations short_fops = {
	.owner	 = THIS_MODULE,
	.read	 = short_read,
	.write	 = short_write,
	.poll	 = short_poll,
	.open	 = short_open,
	.release = short_release,
};

/* then,  the interrupt-related device */

ssize_t short_i_read (struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
{
	int count0;
	DEFINE_WAIT(wait);

	while (short_head == short_tail) {
		prepare_to_wait(&short_queue, &wait, TASK_INTERRUPTIBLE);
		if (short_head == short_tail)
			schedule();
		finish_wait(&short_queue, &wait);
		if (signal_pending (current))  /* a signal arrived */
			return -ERESTARTSYS; /* tell the fs layer to handle it */
	} 
	/* count0 is the number of readable data bytes */
	count0 = short_head - short_tail;
	if (count0 < 0) /* wrapped */
		count0 = short_buffer + PAGE_SIZE - short_tail;
	if (count0 < count) count = count0;

	if (copy_to_user(buf, (char *)short_tail, count))
		return -EFAULT;
	short_incr_bp (&short_tail, count);
	return count;
}

ssize_t short_i_write (struct file *filp, const char __user *buf, size_t count,
		loff_t *f_pos)
{
	int written = 0, odd = *f_pos & 1;
	unsigned long port = short_base; /* output to the parallel data latch */
	void *address = (void *) short_base;

	if (use_mem) {
		while (written < count)
			iowrite8(0xff * ((++written + odd) & 1), address);
	} else {
		while (written < count)
			outb(0xff * ((++written + odd) & 1), port);
	}

	*f_pos += count;
	return written;
}




struct file_operations short_i_fops = {
	.owner	 = THIS_MODULE,
	.read	 = short_i_read,
	.write	 = short_i_write,
	.open	 = short_open,
	.release = short_release,
};

irqreturn_t short_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
	struct timeval tv;
	int written;

	do_gettimeofday(&tv);

	    /* Write a 16 byte record. Assume PAGE_SIZE is a multiple of 16 */
	written = sprintf((char *)short_head,"%08u.%06u\n",
			(int)(tv.tv_sec % 100000000), (int)(tv.tv_usec));
	BUG_ON(written != 16);
	short_incr_bp(&short_head, written);