sbull.c

本源码是将述嵌入式LINUX驱动程序例程

/*
 * sbull.c -- the Simple Block Utility
 *
 * 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: sbull.c,v 1.32 2001/07/18 22:28:16 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/malloc.h> /* kmalloc() */
#include <linux/fs.h>     /* everything... */
#include <linux/errno.h>  /* error codes */
#include <linux/timer.h>
#include <linux/types.h>  /* size_t */
#include <linux/fcntl.h>        /* O_ACCMODE */
#include <linux/hdreg.h>  /* HDIO_GETGEO */

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

#define MAJOR_NR sbull_major /* force definitions on in blk.h */
static int sbull_major; /* must be declared before including blk.h */

#define DEVICE_NR(device) MINOR(device)   /* sbull has no partition bits */
#define DEVICE_NAME "sbull"               /* name for messaging */
#define DEVICE_INTR sbull_intrptr         /* pointer to the bottom half */
#define DEVICE_NO_RANDOM                  /* no entropy to contribute */
#define DEVICE_REQUEST sbull_request
#define DEVICE_OFF(d) /* do-nothing */

#include <linux/blk.h>

#include "sbull.h"        /* local definitions */
#ifdef HAVE_BLKPG_H
#include <linux/blkpg.h>  /* blk_ioctl() */
#endif

/*
 * Do the raw char interface in 2.4.
 */
#ifdef LINUX_24
#  define DO_RAW_INTERFACE
#  include <linux/iobuf.h>
static void sbullr_init();
static void sbullr_release();
#  define SBULLR_SECTOR 512  /* insist on this */
#  define SBULLR_SECTOR_MASK (SBULLR_SECTOR - 1)
#  define SBULLR_SECTOR_SHIFT 9
#endif

/*
 * Non-prefixed symbols are static. They are meant to be assigned at
 * load time. Prefixed symbols are not static, so they can be used in
 * debugging. They are hidden anyways by register_symtab() unless
 * SBULL_DEBUG is defined.
 */
static int major    = SBULL_MAJOR;
static int devs     = SBULL_DEVS;
static int rahead   = SBULL_RAHEAD;
static int size     = SBULL_SIZE;
static int blksize  = SBULL_BLKSIZE;
static int hardsect = SBULL_HARDSECT;

MODULE_PARM(major, "i");
MODULE_PARM(devs, "i");
MODULE_PARM(rahead, "i");
MODULE_PARM(size, "i");
MODULE_PARM(blksize, "i");
MODULE_PARM(hardsect, "i");
MODULE_AUTHOR("Alessandro Rubini");


int sbull_devs, sbull_rahead, sbull_size;
int sbull_blksize, sbull_hardsect;

/* The following items are obtained through kmalloc() in sbull_init() */

Sbull_Dev *sbull_devices = NULL;
int *sbull_blksizes = NULL;
int *sbull_sizes = NULL;
int *sbull_hardsects = NULL;

/*
 * We can do without a request queue, but only in 2.4
 */
#if defined(LINUX_24) && !defined(SBULL_MULTIQUEUE)
static int noqueue = 0;         /* Use request queue by default */
MODULE_PARM(noqueue, "i");
#endif

#ifdef DO_RAW_INTERFACE
int sbullr_major = SBULLR_MAJOR;
MODULE_PARM(sbullr_major, "i");
#endif


int sbull_revalidate(kdev_t i_rdev);


/*
 * Open and close
 */

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

    if (num >= sbull_devs) return -ENODEV;
    dev = sbull_devices + num;
    /* kill the timer associated to the device: it might be active */
    del_timer(&dev->timer);


    spin_lock(&dev->lock);
    /* revalidate on first open and fail if no data is there */
    if (!dev->usage) {
        check_disk_change(inode->i_rdev);
        if (!dev->data)
        {
            spin_unlock (&dev->lock);
            return -ENOMEM;
        }
    }
    dev->usage++;
    spin_unlock(&dev->lock);
    MOD_INC_USE_COUNT;
    return 0;          /* success */
}

int sbull_release (struct inode *inode, struct file *filp)
{
    Sbull_Dev *dev = sbull_devices + MINOR(inode->i_rdev);

    spin_lock(&dev->lock);
    dev->usage--;
    /*
     * If the device is closed for the last time, start a timer
     * to release RAM in half a minute. The function and argument
     * for the timer have been setup in sbull_init()
     */
    if (!dev->usage) {
        dev->timer.expires = jiffies + 30 * HZ;
        add_timer(&dev->timer);
        /* but flush it right now */
        fsync_dev(inode->i_rdev);
        invalidate_buffers(inode->i_rdev);
    }
    MOD_DEC_USE_COUNT;
    spin_unlock(&dev->lock);
    return 0;
}


/*
 * The timer function. As argument it receives the device
 */
void sbull_expires(unsigned long data)
{
    Sbull_Dev *dev = (Sbull_Dev *)data;

    spin_lock(&dev->lock);
    if (dev->usage || !dev->data) {
        spin_unlock(&dev->lock);
        printk(KERN_WARNING "sbull: timer mismatch for device %i\n",
               dev - sbull_devices);
        return;
    }
    PDEBUG("freeing device %i\n",dev - sbull_devices);
    vfree(dev->data);
    dev->data=0;
    spin_unlock(&dev->lock);
    return;
}    

/*
 * The ioctl() implementation
 */

int sbull_ioctl (struct inode *inode, struct file *filp,
                 unsigned int cmd, unsigned long arg)
{
    int err;
    long size;
    struct hd_geometry geo;

    PDEBUG("ioctl 0x%x 0x%lx\n", cmd, arg);
    switch(cmd) {

      case BLKGETSIZE:
        /* Return the device size, expressed in sectors */
        if (!arg) return -EINVAL; /* NULL pointer: not valid */
        err = ! access_ok (VERIFY_WRITE, arg, sizeof(long));
        if (err) return -EFAULT;
        size = blksize*sbull_sizes[MINOR(inode->i_rdev)]
		/ sbull_hardsects[MINOR(inode->i_rdev)];
	if (copy_to_user((long *) arg, &size, sizeof (long)))
	    return -EFAULT;
        return 0;

      case BLKRRPART: /* re-read partition table: can't do it */
        return -ENOTTY;

      case HDIO_GETGEO:
        /*
	 * Get geometry: since we are a virtual device, we have to make
	 * up something plausible.  So we claim 16 sectors, four heads,
	 * and calculate the corresponding number of cylinders.  We set the
	 * start of data at sector four.
         */
        err = ! access_ok(VERIFY_WRITE, arg, sizeof(geo));
        if (err) return -EFAULT;
        size = sbull_size * blksize / sbull_hardsect;
        geo.cylinders = (size & ~0x3f) >> 6;
	geo.heads = 4;
	geo.sectors = 16;
	geo.start = 4;
	if (copy_to_user((void *) arg, &geo, sizeof(geo)))
	    return -EFAULT;
        return 0;

      default:
        /*
         * For ioctls we don't understand, let the block layer handle them.
         */
        return blk_ioctl(inode->i_rdev, cmd, arg);
    }

    return -ENOTTY; /* unknown command */
}

/*
 * Support for removable devices
 */

int sbull_check_change(kdev_t i_rdev)
{
    int minor = MINOR(i_rdev);
    Sbull_Dev *dev = sbull_devices + minor;

    if (minor >= sbull_devs) /* paranoid */ 
        return 0;                           
                                            
    PDEBUG("check_change for dev %i\n",minor);
    if (dev->data)
        return 0; /* still valid */
    return 1; /* expired */
}


/*
 * Note no locks taken out here.  In a worst case scenario, we could drop
 * a chunk of system memory.  But that should never happen, since validation
 * happens at open or mount time, when locks are held.
 */
int sbull_revalidate(kdev_t i_rdev)
{
    Sbull_Dev *dev = sbull_devices + MINOR(i_rdev);

    PDEBUG("revalidate for dev %i\n",MINOR(i_rdev));
    if (dev->data)
        return 0;
    dev->data = vmalloc(dev->size);
    if (!dev->data)
        return -ENOMEM;
    return 0;
}

/*
 * The file operations
 */

#ifdef LINUX_24
struct block_device_operations sbull_bdops = {
    open:               sbull_open,
    release:            sbull_release,
    ioctl:              sbull_ioctl,
    check_media_change: sbull_check_change,
    revalidate:         sbull_revalidate,
};
#else

#ifdef LINUX_20
void sbull_release_20 (struct inode *inode, struct file *filp)
{
        (void) sbull_release (inode, filp);
}
#define sbull_release sbull_release_20
#endif

struct file_operations sbull_bdops = {
    read:       block_read,
    write:      block_write,
    ioctl:      sbull_ioctl,
    open:       sbull_open,
    release:    sbull_release,
    fsync:      block_fsync,
    check_media_change: sbull_check_change,
    revalidate: sbull_revalidate
};
# endif /* LINUX_24 */




/*
 * Block-driver specific functions
 */

/*
 * Find the device for this request.
 */
static Sbull_Dev *sbull_locate_device(const struct request *req)
{
    int devno;
    Sbull_Dev *device;

    /* Check if the minor number is in range */
    devno = DEVICE_NR(req->rq_dev);
    if (devno >= sbull_devs) {
        static int count = 0;
        if (count++ < 5) /* print the message at most five times */
            printk(KERN_WARNING "sbull: request for unknown device\n");
        return NULL;
    }
    device = sbull_devices + devno;  /* Pick it out of our device array */
    return device;
}


/*
 * Perform an actual transfer.
 */
static int sbull_transfer(Sbull_Dev *device, const struct request *req)
{
    int size;
    u8 *ptr;
    
    ptr = device->data + req->sector * sbull_hardsect;
    size = req->current_nr_sectors * sbull_hardsect;

    /* Make sure that the transfer fits within the device. */
    if (ptr + size > device->data + sbull_blksize*sbull_size) {
        static int count = 0;
        if (count++ < 5)
            printk(KERN_WARNING "sbull: request past end of device\n");
        return 0;
    }

    /* Looks good, do the transfer. */
    switch(req->cmd) {
        case READ:
            memcpy(req->buffer, ptr, size); /* from sbull to buffer */
            return 1;
        case WRITE:
            memcpy(ptr, req->buffer, size); /* from buffer to sbull */
            return 1;
        default:
            /* can't happen */
            return 0;
    }
}


#ifdef LINUX_24

/*
 * Transfer a buffer directly, without going through the request queue.
 */
int sbull_make_request(request_queue_t *queue, int rw, struct buffer_head *bh)
{
    u8 *ptr;

    /* Figure out what we are doing */
    Sbull_Dev *device = sbull_devices + MINOR(bh->b_rdev);
    ptr = device->data + bh->b_rsector * sbull_hardsect;

    /* Paranoid check, this apparently can really happen */
    if (ptr + bh->b_size > device->data + sbull_blksize*sbull_size) {
        static int count = 0;
        if (count++ < 5)
            printk(KERN_WARNING "sbull: request past end of device\n");
        bh->b_end_io(bh, 0);
        return 0;
    }

    /* This could be a high memory buffer, shift it down */
#if CONFIG_HIGHMEM
    bh = create_bounce(rw, bh);
#endif

    /* Do the transfer */
    switch(rw) {
        case READ:
        case READA:  /* Readahead */
            memcpy(bh->b_data, ptr, bh->b_size); /* from sbull to buffer */
            bh->b_end_io(bh, 1);
            break;
        case WRITE:
            refile_buffer(bh);
            memcpy(ptr, bh->b_data, bh->b_size); /* from buffer to sbull */
            mark_buffer_uptodate(bh, 1);
            bh->b_end_io(bh, 1);
            break;
        default:
            /* can't happen */
            bh->b_end_io(bh, 0);
            break;
    }

    /* Nonzero return means we're done */
    return 0;
}


void sbull_unused_request(request_queue_t *q)
{
    static int count = 0;
    if (count++ < 5)
        printk(KERN_WARNING "sbull: unused_request called\n");
}
        
#endif /* LINUX_24 */



#if defined(SBULL_EMPTY_REQUEST)
/*
 * This empty request function just prints the interesting items
 * of the current request. The sectors affected by the request
 * are printed as <first-sector>-<number-of-sectors>.
 */
#ifdef LINUX_24
void sbull_request(request_queue_t *q)
#else                                   
void sbull_request()