linux驱动9--ldd中第三章scull

一. 一个简洁的scull_ch3
在看的第三章 字符设备驱动程序时,发现源码中没有比较简洁的scull,(类似于helloworld,只包含所讲的内容的代码).
下面就整一个scull_ch3,
         a. 只包含所讲的内容,文件操作接口只有 open read write release
         b. 删去了 proc pipe等以后章节讲的代码
         c. 增加了自动创建设备节点,省去了手动mknod的麻烦.

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>    /* printk() */
#include <linux/slab.h>      /* kmalloc() */
#include <linux/fs.h>        /* everything... */
#include <linux/errno.h>     /* error codes */
#include <linux/types.h>     /* size_t */
#include <linux/seq_file.h>
#include <linux/cdev.h>
#include <linux/device.h>    /*class device*/

#include <asm/uaccess.h>     /*copy_from_user*/

#define SCULL_MAJOR 0        /* dynamic major by default */
#define SCULL_NR_DEVS 4      /* scull0 through scull3 */
#define SCULL_QUANTUM 4000
#define SCULL_QSET    1000

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;

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 */
    struct cdev cdev;            /* Char device structure        */
    struct class *cls;
};
struct scull_dev *scull_devices;

int scull_trim(struct scull_dev *dev)
{
    struct scull_qset *next, *dptr;
    int qset = dev->qset;      /* "dev" is not-null */
    int i;
    /* all the list items */
    for (dptr = dev->data; dptr; dptr = next) {
        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->quantum = scull_quantum;
    dev->qset = scull_qset;
    dev->data = NULL;
    return 0;
}
static int scull_open(struct inode* node, struct file *filp)
{
    struct scull_dev *dev; /* device information */

    dev = container_of(node->i_cdev, struct scull_dev, cdev);
    filp->private_data = dev;
    return 0; /* success */
}

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;
}


static 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 (*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:
    return retval;
}

static 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 */


    /* 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:
    return retval;
}

static int scull_release(struct inode *node, struct file* filp)
{
    printk(KERN_ALERT "scull release!\n");
    return 0;
}
static const struct file_operations scull_fops =
{
    .owner = THIS_MODULE,
    .open = scull_open,
    .read = scull_read,
    .write = scull_write,
    .release = scull_release,
};

static void __exit scull_exit(void)
{
    int i;
    dev_t devno = MKDEV(scull_major, scull_minor);

    printk(KERN_ALERT "goodbye scull dirver\n");
    /* 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);
            //以下去掉增加自动创建的设备结点
            device_destroy(scull_devices[i].cls, MKDEV(scull_major, i));
            class_destroy(scull_devices[i].cls);
        }
        kfree(scull_devices);
    }
    unregister_chrdev_region(devno, scull_nr_devs);
    return ;
}

static void scull_setup_cdev(struct scull_dev *dev, int index)
{
    int err, devno = MKDEV(scull_major, scull_minor + index);
    char buf[128];
    memset(buf, 0, sizeof(buf));

    cdev_init(&dev->cdev, &scull_fops);
    dev->cdev.owner = THIS_MODULE;
    dev->cdev.ops = &scull_fops;
    err = cdev_add (&dev->cdev, devno, 1);
    if (err)
        printk(KERN_NOTICE "Error %d adding scull%d", err, index);
    //以下增加自动创建设备结点
    sprintf(buf, "scull_class%d", index);
    dev->cls = class_create(THIS_MODULE, buf);
    if(IS_ERR(dev->cls))
        printk(KERN_ALERT "class create error!\n");

    device_create(dev->cls, NULL, devno, NULL, buf);
}

static int __init scull_init(void)
{
    int result, i;
    dev_t dev = 0;
    printk(KERN_NOTICE "scull_init\n");
    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);
        goto fail;
    }

    /* 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;
        scull_setup_cdev(&scull_devices[i], i);
    }
    return 0;
fail:
  scull_exit();
  return result;
}

MODULE_LICENSE("GPL");
MODULE_AUTHOR("wangcong02345");
module_init(scull_init);
module_exit(scull_exit);

附代码下载:
ch3_scull.rar 
下载后改名: ch3_scull.tar.gz