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分类: LINUX

2010-10-19 17:32:51




/*
* scull.h
*/


#ifndef _SCULL_H_
#define _SCULL_H_

#undef PDEBUG

#ifdef SCULL_DEBUG
    #ifdef __KERNEL__ /* just in kernel space */
        #define PDEBUG(fmt, args...) printk( KERN_DEBUG "scull: " fmt, ## args)
    #else /* debug on in user space */
        #define PDEBUG(fmt, args...) fprintf(stderr, fmt, ## args)
    #endif
#else /* #ifndef SCULL_DEBUG */
    #define PDEBUG(fmt, args...) /* not debugging: nothing */
#endif /* SCULL_DEBUG */

#ifndef SCULL_MAJOR
#define SCULL_MAJOR        0 /* dynamic major by default */
#endif

#ifndef SCULL_NR_DEVS
#define SCULL_NR_DEVS 4 /* scull0 through scull3 */
#endif

#ifndef SCULL_P_NR_DEVS
#define SCULL_P_NR_DEVS 4 /* scullpipe0 through scullpipe3 */
#endif

/*
 * The bare device is a variable-length region of memory.
 * Use a linked list of indirect blocks.
 *
 * "scull_dev->data" points to an array of pointers
 * The array (quantum-set) is SCULL_QSET long.
 * each pointer refers to a memory area of SCULL_QUANTUM bytes.
 */

#ifndef SCULL_QSET
#define SCULL_QSET 1000
#endif

#ifndef SCULL_QUANTUM
#define SCULL_QUANTUM 4000
#endif

/*
 * The pipe device is a simple circular buffer. Here its default size
 */

#ifndef SCULL_P_BUFFER
#define SCULL_P_BUFFER 4000
#endif

/*
 * Representation of scull quantum sets.
 */

struct scull_qset {
    void **data;
    struct scull_qset *next;
};

struct scull_dev {
    struct scull_qset *data; /* Pointer to first quantum set */
    int quantum; /* the current quantum size */
    int qset; /* the current array size */
    unsigned long size; /* amount of data stored here */
    unsigned int access_key; /* used by sculluid and scullpriv */
    struct semaphore sem; /* mutual exclusion semaphore */
    struct cdev cdev;     /* Char device structure        */
};

/*
 * The different configurable parameters
 */

extern int scull_major;
extern int scull_nr_devs;
extern int scull_quantum;
extern int scull_qset;

/*
 * Prototypes for shared functions
 */

int scull_trim(struct scull_dev *dev);

ssize_t scull_read(struct file *filp, char __user *buf, size_t count,
                   loff_t *f_pos);
ssize_t scull_write(struct file *filp, const char __user *buf, size_t count,
                    loff_t *f_pos);

#endif


/*
* scull.c
* 4 个设备, scrull0 - scrull3.
    每个设备由一个全局永久的内存区组成,全局代表能重入,永久代表设备关闭和重新打开不会引起数据丢失。
* 4 个FIFO scrullpipe0 - scrullpipe3
    设备重入时可能引起多进程的数据竞争, FIFO代替终中断描述阻塞和非阻塞读写的实现。
* scrullsingle
    只允许一次一个进程使用驱动
* scrullpriv
    每个设备的私有数据
* scrulluid / scrullwuid
    设置设备可以多次打开,但一次只能是一个用户, 否则scrulluid返回设备忙。 scrullwuid实现阻塞打开。
*/


#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/errno.h>    /* error codes */
#include <linux/kernel.h>    /* printk() */
#include <linux/types.h> /* dev_t */
#include <asm/uaccess.h>    /* copy_*_user */

#include <linux/fs.h> /* file_operations file inode*/
#include <linux/cdev.h> /* struct cdev */
#include <linux/slab.h>        /* kmalloc() */
#include <linux/fcntl.h>    /* O_ACCMODE */

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

/*
 * Our parameters which can be set at load time.
 */

int scull_major = SCULL_MAJOR;
int scull_minor = 0;
int scull_nr_devs = SCULL_NR_DEVS;    /* number of bare scull devices */
int scull_quantum = SCULL_QUANTUM;
int scull_qset = SCULL_QSET;

module_param(scull_major, int, S_IRUGO);
module_param(scull_minor, int, S_IRUGO);
module_param(scull_nr_devs, int, S_IRUGO);
module_param(scull_quantum, int, S_IRUGO);
module_param(scull_qset, int, S_IRUGO);

struct scull_dev *scull_devices;    /* allocated in scull_init_module */

/*
 * Empty out the scull device; must be called with the device
 * semaphore held.
 */

int scull_trim(struct scull_dev *dev)
{
    struct scull_qset *next, *dptr;
    int qset = dev->qset; /* "dev" is not-null */
    int i;

    for (dptr = dev->data; dptr; dptr = next) { /* all the list items */
        if (dptr->data) {
            for (i = 0; i < qset; i++)
                kfree(dptr->data[i]);
            kfree(dptr->data);
            dptr->data = NULL;
        }
        next = dptr->next;
        kfree(dptr);
    }
    dev->size = 0;
    dev->qset = scull_qset;
    dev->quantum = scull_quantum;
    dev->data = NULL;
    return 0;
}

/*
 * Open and close
 */

int scull_open(struct inode *inode, struct file *filp)
{
    struct scull_dev *dev; /* device information */

    dev = container_of(inode->i_cdev, struct scull_dev, cdev);
    filp->private_data = dev; /* for other methods */

    /* 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;
        scull_trim(dev); /* ignore errors */
        up(&dev->sem);
    }
    return 0; /* success */
}

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

/*
 * Follow the list
 */

struct scull_qset *scull_follow(struct scull_dev *dev, int n)
{
    struct scull_qset *qs = dev->data;

        /* Allocate first qset explicitly if need be */
    if (! qs) {
        qs = dev->data = kmalloc(sizeof(struct scull_qset), GFP_KERNEL);
        if (qs == NULL)
            return NULL; /* Never mind */
        memset(qs, 0, sizeof(struct scull_qset));
    }

    /* Then follow the list */
    while (n--) {
        if (!qs->next) {
            qs->next = kmalloc(sizeof(struct scull_qset), GFP_KERNEL);
            if (qs->next == NULL)
                return NULL; /* Never mind */
            memset(qs->next, 0, sizeof(struct scull_qset));
        }
        qs = qs->next;
        continue;
    }
    return qs;
}

/*
 * Data management: read and write
 */


ssize_t scull_read(struct file *filp, char __user *buf, size_t count,
                loff_t *f_pos)
{
    struct scull_dev *dev = filp->private_data;
    struct scull_qset *dptr;    /* the first listitem */
    int quantum = dev->quantum, 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 out;
    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 = scull_follow(dev, item);

    if (dptr == NULL || !dptr->data || ! dptr->data[s_pos])
        goto out; /* don't fill holes */

    /* read only up to the end of this quantum */
    if (count > quantum - q_pos)
        count = quantum - q_pos;

    if (copy_to_user(buf, dptr->data[s_pos] + q_pos, count)) {
        retval = -EFAULT;
        goto out;
    }
    *f_pos += count;
    retval = count;

  out:
    up(&dev->sem);
    return retval;
}

ssize_t scull_write(struct file *filp, const char __user *buf, size_t count,
                loff_t *f_pos)
{
    struct scull_dev *dev = filp->private_data;
    struct scull_qset *dptr;
    int quantum = dev->quantum, qset = dev->qset;
    int itemsize = quantum * qset;
    int item, s_pos, q_pos, rest;
    ssize_t retval = -ENOMEM; /* value used in "goto out" statements */

    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 = scull_follow(dev, item);
    if (dptr == NULL)
        goto out;
    if (!dptr->data) {
        dptr->data = kmalloc(qset * sizeof(char *), GFP_KERNEL);
        if (!dptr->data)
            goto out;
        memset(dptr->data, 0, qset * sizeof(char *));
    }
    if (!dptr->data[s_pos]) {
        dptr->data[s_pos] = kmalloc(quantum, GFP_KERNEL);
        if (!dptr->data[s_pos])
            goto out;
    }
    /* write only up to the end of this quantum */
    if (count > quantum - q_pos)
        count = quantum - q_pos;

    if (copy_from_user(dptr->data[s_pos]+q_pos, buf, count)) {
        retval = -EFAULT;
        goto out;
    }
    *f_pos += count;
    retval = count;

        /* update the size */
    if (dev->size < *f_pos)
        dev->size = *f_pos;

  out:
    up(&dev->sem);
    return retval;
}

struct file_operations scull_fops = {
    .owner = THIS_MODULE,
    .read = scull_read,
    .write = scull_write,
    .open = scull_open,
    .release = scull_release,
};

/*
 * Set up the char_dev structure for this device.
 */

static void scull_setup_cdev(struct scull_dev *dev, int index)
{
    int err, devno = MKDEV(scull_major, scull_minor + index);
    
    cdev_init(&dev->cdev, &scull_fops);
    dev->cdev.owner = THIS_MODULE;
    err = cdev_add (&dev->cdev, devno, 1);
    /* Fail gracefully if need be */
    if (err)
        printk(KERN_NOTICE "Error %d adding scull%d", err, index);
}

/*
 * The cleanup function is used to handle initialization failures as well.
 * Thefore, it must be careful to work correctly even if some of the items
 * have not been initialized
 */

void scull_cleanup_module(void)
{
    int i;
    dev_t devno = MKDEV(scull_major, scull_minor);

    /* Get rid of our char dev entries */
    if (scull_devices) {
        for (i = 0; i < scull_nr_devs; i++) {
            scull_trim(scull_devices + i);
            cdev_del(&scull_devices[i].cdev);
        }
        kfree(scull_devices);
    }

    /* cleanup_module is never called if registering failed */
    unregister_chrdev_region(devno, scull_nr_devs);
}

int scull_init_module(void)
{
    int result, i;
    dev_t dev = 0;

    /*
     * Get a range of minor numbers to work with, asking for a dynamic
     * major unless directed otherwise at load time.
     */

    if (scull_major) {
        dev = MKDEV(scull_major, scull_minor);
        result = register_chrdev_region(dev, scull_nr_devs, "scull");
    } else {
        result = alloc_chrdev_region(&dev, scull_minor, scull_nr_devs,
                "scull");
        scull_major = MAJOR(dev);
    }
    if (result < 0) {
        printk(KERN_WARNING "scull: can't get major %d\n", scull_major);
        return result;
    }

    /*
     * allocate the devices -- we can't have them static, as the number
     * can be specified at load time
     */

    scull_devices = kmalloc(scull_nr_devs * sizeof(struct scull_dev), GFP_KERNEL);
    if (!scull_devices) {
        result = -ENOMEM;
        goto fail; /* Make this more graceful */
    }
    memset(scull_devices, 0, scull_nr_devs * sizeof(struct scull_dev));

        /* Initialize each device. */
    for (i = 0; i < scull_nr_devs; i++) {
        scull_devices[i].quantum = scull_quantum;
        scull_devices[i].qset = scull_qset;
        init_MUTEX(&scull_devices[i].sem);
        scull_setup_cdev(&scull_devices[i], i);
    }

    return 0; /* succeed */

fail:
    scull_cleanup_module();
    return result;
}

module_init(scull_init_module);
module_exit(scull_cleanup_module);

MODULE_LICENSE("Dual BSD/GPL");


#Makefile


TARGETOBJ := scull
obj-m := $(TARGETOBJ).o

# If KERNELRELEASE is defined, we've been invoked from the

# kernel build system and can use its language.

ifeq ($(KERNELRELEASE),) # if Make just in current path


#CROSS_COMPILE := arm-none-linux-gnueabi-

#CC := $(CROSS_COMPILE)gcc


KERNELDIR := /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)
BASENAME := $(shell basename $(PWD))

SRCDIR := .
SRCEXT := .c

SOURCEFILE := $(foreach ext,$(SRCEXT), \
    $(foreach sd, $(SRCDIR), $(wildcard $(addprefix $(sd)/*,$(ext)))))

SRCOBJS := $(foreach ext, $(SRCEXT), \
    $(patsubst %$(ext), %.o, $(filter %$(ext),$(SOURCEFILE))))

obj-m := $(TARGETOBJ).o
$(TARGETOBJ)-objs := $(SRCOBJS)

default:
    $(MAKE) -C $(KERNELDIR) M=$(PWD) modules

clean:
    @touch $(TARGETOBJ).ko
    @mv $(TARGETOBJ).ko $(TARGETOBJ).ko.lasted
    $(MAKE) -C $(KERNELDIR) M=$(PWD) clean
       
endif    



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