main.c

本源码是将述嵌入式LINUX驱动程序例程

/* -*- C -*-
 * main.c -- the bare scullc char module
 *
 * 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: _main.c.in,v 1.19 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>

/* modversion stuff: no #ifdef needed if 2.0 support is not needed */
#ifdef CONFIG_MODVERSIONS
#  include <linux/modversions.h>
#endif

#include <linux/kernel.h> /* printk() */
#include <linux/malloc.h> /* kmalloc() */
#include <linux/fs.h>     /* everything... */
#include <linux/errno.h>  /* error codes */
#include <linux/types.h>  /* size_t */
#include <linux/proc_fs.h>
#include <linux/fcntl.h>        /* O_ACCMODE */

#include <asm/system.h>   /* cli(), *_flags */

#include "scullc.h"        /* local definitions */

/* Kmem caches were not available in 2.0. Disallow compilation in that case */
#ifdef LINUX_20
#  error "Kmem_cache functions are not available in Linux-2.0"
#else
#  if defined(LINUX_22) && LINUX_VERSION_CODE < KERNEL_VERSION(2,2,18)
#    error "This module needs at least 2.2.18 to run"
#  endif
/* leave the #ifdef open, so 2.0 won't get other errors */


/*
 * I don't use static symbols here, because register_symtab is called
 */

int scullc_major =   SCULLC_MAJOR;
int scullc_devs =    SCULLC_DEVS;    /* number of bare scullc devices */
int scullc_qset =    SCULLC_QSET;
int scullc_quantum = SCULLC_QUANTUM;

MODULE_PARM(scullc_major, "i");
MODULE_PARM(scullc_devs, "i");
MODULE_PARM(scullc_qset, "i");
MODULE_PARM(scullc_quantum, "i");
MODULE_AUTHOR("Alessandro Rubini");


ScullC_Dev *scullc_devices; /* allocated in scullc_init */

int scullc_trim(ScullC_Dev *dev);

/* declare one cache pointer: use it for all devices */
kmem_cache_t *scullc_cache;

#ifdef SCULLC_USE_PROC /* don't waste space if unused */
/*
 * The proc filesystem: function to read and entry
 */

void scullc_proc_offset(char *buf, char **start, off_t *offset, int *len)
{
    if (*offset == 0)
        return;
    if (*offset >= *len) {      /* Not there yet */
        *offset -= *len;
        *len = 0;
    }
    else {                      /* We're into the interesting stuff now */
        *start = buf + *offset;
        *offset = 0;
    }
}

int scullc_read_procmem(char *buf, char **start, off_t offset,
                   int count, int *eof, void *data)
{
    int i, j, quantum, qset, len = 0;
    int limit = count - 80; /* Don't print more than this */
    ScullC_Dev *d;

    *start = buf;
    for(i=0; i<scullc_devs; i++) {
        d=&scullc_devices[i];
        if (down_interruptible (&d->sem))
                return -ERESTARTSYS;
        qset=d->qset;  /* retrieve the features of each device */
        quantum=d->quantum;
        len += sprintf(buf+len,"\nDevice %i: qset %i, quantum %i, sz %li\n",
                       i, qset, quantum, (long)(d->size));
        for (; d; d=d->next) { /* scan the list */
            len += sprintf(buf+len,"  item at %p, qset at %p\n",d,d->data);
            scullc_proc_offset (buf, start, &offset, &len);
            if (len > limit)
                goto out;
            if (d->data && !d->next) /* dump only the last item - save space */
                for (j=0; j<qset; j++) {
                    if (d->data[j])
                        len += sprintf(buf+len,"    % 4i:%8p\n",j,d->data[j]);
                    scullc_proc_offset (buf, start, &offset, &len);
                    if (len > limit)
                        goto out;
		}
        }
    out:
        up (&scullc_devices[i].sem);
	if (len > limit)
	    break;
    }
    *eof = 1;
    return len;
}

#ifdef USE_PROC_REGISTER

static int scullc_get_info (char *buf, char **start, off_t offset,
                int len, int unused)
{
    int eof = 0;
    return scullc_read_procmem(buf, start, offset, len, &eof, NULL);
}


struct proc_dir_entry scullc_proc_entry = {
        0,                 /* low_ino: the inode -- dynamic */
        9, "scullcmem",     /* len of name and name */
        S_IFREG | S_IRUGO, /* mode */
        1, 0, 0,           /* nlinks, owner, group */
        0, NULL,           /* size - unused; operations -- use default */
        scullc_get_info,   /* function used to read data */
        /* nothing more */
    };


static inline void create_proc_read_entry (const char *name, mode_t mode,
                struct proc_dir_entry *base, void *read_func, void *data)
{
    proc_register_dynamic (&proc_root, &scullc_proc_entry);
}

static inline void remove_proc_entry (char *name, void *parent)
{
    proc_unregister (&proc_root, scullc_proc_entry.low_ino);
}

#endif /* USE_PROC_REGISTER */
#endif /* SCULLC_USE_PROC */

/*
 * Open and close
 */

int scullc_open (struct inode *inode, struct file *filp)
{
    int num = MINOR(inode->i_rdev);
    ScullC_Dev *dev; /* device information */

    /*  check the device number */
    if (num >= scullc_devs) return -ENODEV;
    dev = &scullc_devices[num];

    /* now trim to 0 the length of the device if open was write-only */
     if ( (filp->f_flags & O_ACCMODE) == O_WRONLY) {
        if (down_interruptible (&dev->sem))
            return -ERESTARTSYS;
        scullc_trim(dev); /* ignore errors */
        up (&dev->sem);
    }

    /* and use filp->private_data to point to the device data */
    filp->private_data = dev;

    MOD_INC_USE_COUNT;
    return 0;          /* success */
}

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

/*
 * Follow the list 
 */
ScullC_Dev *scullc_follow(ScullC_Dev *dev, int n)
{
    while (n--) {
        if (!dev->next) {
            dev->next = kmalloc(sizeof(ScullC_Dev), GFP_KERNEL);
            memset(dev->next, 0, sizeof(ScullC_Dev));
        }
        dev = dev->next;
        continue;
    }
    return dev;
}

/*
 * Data management: read and write
 */

ssize_t scullc_read (struct file *filp, char *buf, size_t count,
                loff_t *f_pos)
{
    ScullC_Dev *dev = filp->private_data; /* the first listitem */
    ScullC_Dev *dptr;
    int quantum = dev->quantum;
    int qset = dev->qset;
    int itemsize = quantum * qset; /* how many bytes in the listitem */
    int item, s_pos, q_pos, rest;
    ssize_t retval = 0;

    if (down_interruptible (&dev->sem))
            return -ERESTARTSYS;
    if (*f_pos > dev->size) 
        goto nothing;
    if (*f_pos + count > dev->size)
        count = dev->size - *f_pos;
    /* find listitem, qset index, and offset in the quantum */
    item = ((long) *f_pos) / itemsize;
    rest = ((long) *f_pos) % itemsize;
    s_pos = rest / quantum; q_pos = rest % quantum;

    /* follow the list up to the right position (defined elsewhere) */
    dptr = scullc_follow(dev, item);

    if (!dptr->data)
        goto nothing; /* don't fill holes */
    if (!dptr->data[s_pos])
        goto nothing;
    if (count > quantum - q_pos)
        count = quantum - q_pos; /* read only up to the end of this quantum */

    if (copy_to_user (buf, dptr->data[s_pos]+q_pos, count)) {
        retval = -EFAULT;
        goto nothing;
    }
    up (&dev->sem);

    *f_pos += count;
    return count;

  nothing:
    up (&dev->sem);
    return retval;
}



ssize_t scullc_write (struct file *filp, const char *buf, size_t count,
                loff_t *f_pos)
{
    ScullC_Dev *dev = filp->private_data;
    ScullC_Dev *dptr;
    int quantum = dev->quantum;
    int qset = dev->qset;
    int itemsize = quantum * qset;
    int item, s_pos, q_pos, rest;
    ssize_t retval = -ENOMEM; /* our most likely error */

    if (down_interruptible (&dev->sem))
            return -ERESTARTSYS;

    /* find listitem, qset index and offset in the quantum */
    item = ((long) *f_pos) / itemsize;
    rest = ((long) *f_pos) % itemsize;
    s_pos = rest / quantum; q_pos = rest % quantum;

    /* follow the list up to the right position */
    dptr = scullc_follow(dev, item);
    if (!dptr->data) {
        dptr->data = kmalloc(qset * sizeof(void *), GFP_KERNEL);
        if (!dptr->data)
            goto nomem;
        memset(dptr->data, 0, qset * sizeof(char *));
    }
    /* Allocate a quantum using the memory cache */
    if (!dptr->data[s_pos]) {
        dptr->data[s_pos] =
	    kmem_cache_alloc(scullc_cache, GFP_KERNEL);