short.c

本源码是将述嵌入式LINUX驱动程序例程

/*
 * 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 1.22 2001/07/18 22:28:18 rubini Exp $
 */

#ifndef __KERNEL__
#  define __KERNEL__
#endif
#ifndef MODULE
#  define MODULE
#endif

#include <linux/config.h>
#include <linux/module.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/malloc.h>
#include <linux/mm.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/tqueue.h>

#include <asm/io.h>

#include "sysdep.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_PARM(major, "i");

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

/* 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_PARM(base, "l");

/* Since short_base is vremapped in case use_mem==1, remember the phys addr. */
unsigned long short_phys;

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

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

static int bh = 0; /* select at load time whether a bottom-half is used */
MODULE_PARM(bh, "i");

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

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

MODULE_AUTHOR ("Alessandro Rubini");




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. */
#ifdef HAVE_TASKLETS
void short_do_tasklet (unsigned long);
DECLARE_TASKLET (short_tasklet, short_do_tasklet, 0);
#endif

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


#ifdef LINUX_20
void short_release (struct inode *inode, struct file *filp)
{
    MOD_DEC_USE_COUNT;
}
#else
int short_release (struct inode *inode, struct file *filp)
{
    MOD_DEC_USE_COUNT;
    return 0;
}
#endif


/* 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 *buf,
                size_t count, loff_t *f_pos)
{
    int retval = count;
    unsigned long address = short_base + (MINOR(inode->i_rdev)&0x0f);
    int mode = (MINOR(inode->i_rdev)&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(address, ptr, count);
	rmb();
        break;

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

      case SHORT_MEMORY:
        while (count--) {
            *(ptr++) = readb(address);
	    rmb();
	}
        break;
      case SHORT_PAUSE:
        while (count--) {
            *(ptr++) = inb_p(address);
	    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.
 */
#ifdef LINUX_20
int short_read(struct inode *inode, struct file *filp, char *buf, int count)
{
    return do_short_read(inode, filp, buf, count, &filp->f_pos);
}

#else
ssize_t short_read(struct file *filp, char *buf, size_t count, loff_t *f_pos)
{
    return do_short_read(filp->f_dentry->d_inode, filp, buf, count, f_pos);
}
#endif



ssize_t do_short_write (struct inode *inode, struct file *filp, const char *buf,
                size_t count, loff_t *f_pos)
{
    int retval = count;
    unsigned long address = short_base + (MINOR(inode->i_rdev)&0x0f);
    int mode = (MINOR(inode->i_rdev)&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++), address);
	    wmb();
	}
        break;

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

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

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

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


#ifdef LINUX_20
int short_write(struct inode *inode, struct file *filp, const char *buf,
                int count)
{
    return do_short_write(inode, filp, buf, count, &filp->f_pos);
}

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



#ifdef __USE_OLD_SELECT__
int short_poll (struct inode *inode, struct file *filp,
                  int mode, select_table *table)
{
    return mode==SEL_EX ? 0 : 1; /* readable, writable, not-exceptionable */
}
#define poll select
#else /* Use poll */

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

#endif /* __USE_OLD_SELECT__ */





struct file_operations short_fops = {
    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 *buf, size_t count, loff_t *f_pos)
{
    int count0;

    while (short_head == short_tail) {
        interruptible_sleep_on(&short_queue);
        if (signal_pending (current))  /* a signal arrived */
          return -ERESTARTSYS; /* tell the fs layer to handle it */
        /* else, loop */
    }
    /* 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 *buf, size_t count,
                loff_t *f_pos)
{
    int written = 0, odd = *f_pos & 1;
    unsigned long address = short_base; /* output to the parallel data latch */

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

    *f_pos += count;
    return written;
}


/*
 * 2.0 wrappers.
 */
#ifdef LINUX_20

int short_i_read_20 (struct inode *inode, struct file *filp, char *buf,
                int count)
{
    return short_i_read (filp, buf, count, &filp->f_pos);
}

int short_i_write_20 (struct inode *inode, struct file *filp, const char *buf,
                int count)
{
    return short_i_write (filp, buf, count, &filp->f_pos);
}

#define short_i_read  short_i_read_20
#define short_i_write short_i_write_20

#endif /* LINUX_20 */


struct file_operations short_i_fops = {
    read: short_i_read,
    write: short_i_write,
    open: short_open,
    release: short_release,