基于linux 3.10.49内核添加字符驱动

基于linux 3.10.49内核添加字符驱动

linux kernel 3.10.49+

字符驱动编译进内核.

1.在drivers目录下新建MyDemo目录.

2.MyDemo目录新建三个文件:demo.c  Kconfig  Makefile

3.修改Kconfig文件:

MyDemo-> cat Kconfig

## TPM device configuration#config MY_DEMO bool "my demo test driver!!!"    default y---help---  If you have a TPM security chip that is compliant with the  TCG TIS 1.2 TPM specification say Yes and it will be accessible  from within Linux.  To compile this driver as a module, choose  M here; the module will be called tpm_tis.

这个Kconfig会生成CONFIG_MY_DEMO这个宏, 且默认会生成这个宏, 因为default     y

4.修改Makefile:

MyDemo-> cat Makefile 

obj-$(CONFIG_MY_DEMO) += demo.o

5.修改demo.c:

MyDemo-> cat demo.c

/// @file demo.c/// @brief /// @author EastonWoo <[e-mail]>/// 0.01/// @date 2016-05-26#include <linux/module.h>  #include <linux/cdev.h>  #include <linux/fs.h>  #include <linux/slab.h>  #include <linux/uaccess.h>  #include <linux/types.h>  #include <linux/ioctl.h>    #include <linux/device.h>#define MYDEMO_MAJOR 105#define MYDEMO_MINNOR 9 #define MYDEMO_BUF_LEN 100static loff_t g_llMyDemoPos = 0;static int mydemodev_open(struct inode *inode, struct file *file){unsigned int minor = iminor(inode);    char *demo_buf;demo_buf = kzalloc(MYDEMO_BUF_LEN, GFP_KERNEL);    memset(demo_buf, 0, MYDEMO_BUF_LEN);if (!demo_buf) {return -ENOMEM;}file->private_data = demo_buf;    printk(KERN_WARNING "[%s %s %d] minor = %u\n", __FILE__, __func__, __LINE__, minor);return 0;}static int mydemodev_release(struct inode *inode, struct file *file){unsigned int minor = iminor(inode);    char *demo_buf = file->private_data;kfree(demo_buf);file->private_data = NULL;    printk(KERN_WARNING "[%s %s %d] minor = %u\n", __FILE__, __func__, __LINE__, minor);return 0;}/// @brief ////// @param file/// @param buf          :上层应用read(int fildes, void *buf, size_t nbyte)的buf/// @param count        :上层应用read(int fildes, void *buf, size_t nbyte)的nbyte/// @param offset       :驱动层的 不是 &file->f_pos, 只是一个file->f_pos的数值地址////// @return             :上层应用read(int fildes, void *buf, size_t nbyte)的返回值ssize_t mydemodev_read(struct file *file, char __user *buf, size_t count, loff_t *offset) {    loff_t pos = file->f_pos + count;    size_t really_cnt = count;    int ret = 0;        if (NULL == buf) {        return -EINVAL;    }    if (pos >= MYDEMO_BUF_LEN) {        really_cnt = MYDEMO_BUF_LEN - 1 - file->f_pos;    }    /* ret = copy_to_user(buf, file->private_data + file->f_pos, really_cnt) ? -EFAULT : ret; */  // 不清楚为什么, file->f_pos这个不会变    ret = copy_to_user(buf, file->private_data + g_llMyDemoPos, really_cnt) ? -EFAULT : ret;    if (ret != -EFAULT)        file->f_pos += really_cnt;    printk(KERN_WARNING "[%s %s %d] really_cnt = %d\n", __FILE__, __func__, __LINE__, really_cnt);    g_llMyDemoPos = file->f_pos;    return really_cnt;}/// @brief ////// @param file/// @param buf          :上层应用write(int fildes, const void *buf, size_t nbyte)的buf/// @param count        :上层应用write(int fildes, const void *buf, size_t nbyte)的nbyte/// @param offset       :驱动层的 不是 &file->f_pos, 只是一个file->f_pos的数值地址////// @return             :上层应用write(int fildes, const void *buf, size_t nbyte)的返回值ssize_t mydemodev_write(struct file *file, const char __user *buf, size_t count, loff_t *offset) {    int ret = 0;        if (NULL == buf) {        return -EINVAL;    }    if (file->f_pos + count >= MYDEMO_BUF_LEN) {        return -EINVAL;    }    /* ret = copy_from_user(file->private_data + file->f_pos, buf, count) ? -EFAULT : ret; */ // 不清楚为什么, file->f_pos这个不会变    ret = copy_from_user(file->private_data + g_llMyDemoPos, buf, count) ? -EFAULT : ret;    if (ret != -EFAULT)        file->f_pos += count;    printk(KERN_WARNING "[%s %s %d] count = %d\n", __FILE__, __func__, __LINE__, count);    g_llMyDemoPos = file->f_pos;    return count;}/// @brief ////// @param file/// @param offset   :上层应用lseek(int fd, off_t offset, int whence)的offset/// @param where    :上层应用lseek(int fd, off_t offset, int whence)的whence////// @return         :上层应用lseek(int fd, off_t offset, int whence)的返回值loff_t mydemodev_llseek(struct file *file, loff_t offset, int where) {    // 没有 加锁    loff_t pos = file->f_pos + offset;    switch(where) {        case SEEK_SET:            if (offset >= MYDEMO_BUF_LEN || offset < 0) {                return -EINVAL;            }            file->f_pos = offset;            break;        case SEEK_CUR:        case SEEK_END:            if (pos >= MYDEMO_BUF_LEN || pos < 0) {                return -EINVAL;            }            file->f_pos = pos;            break;        default:            return -EINVAL;            break;    }    printk(KERN_WARNING "[%s %s %d] pos = %lld iminor(file->f_inode) = %u\n", __FILE__, __func__, __LINE__, file->f_pos, iminor(file->f_inode));    g_llMyDemoPos = file->f_pos;    return file->f_pos;}static const struct file_operations mydemodev_fops = {.owner= THIS_MODULE,    .llseek= mydemodev_llseek,                   // 1-2  --|     .read= mydemodev_read,                     // 1-2  --|    .write= mydemodev_write,                    // 1-2  --|这一步写上, 高级操作. // .unlocked_ioctl= i2cdev_ioctl,    .open= mydemodev_open,                     // 1-1  --|    .release= mydemodev_release,                  // 1-1  --| 这一步写上, 基本上就可以看到效果了.};static struct class *mydemo_dev_class;static int __init mydemo_dev_init(void){int res;printk(KERN_INFO "my char dev demo entries driver\n");res = register_chrdev(MYDEMO_MAJOR, "mydemo", &mydemodev_fops);             //1. 注册字符设备if (res)goto out;mydemo_dev_class = class_create(THIS_MODULE, "mydemo-class");               //2. 生成class, 在 /sys/class/ 下生成mydemo-class文件夹if (IS_ERR(mydemo_dev_class)) {res = PTR_ERR(mydemo_dev_class);goto out_unreg_chrdev;}    device_create(mydemo_dev_class,NULL,MKDEV(MYDEMO_MAJOR, MYDEMO_MINNOR),NULL,"mydemo-dev" "%d", MYDEMO_MINNOR); //3. 生成class, 在 /dev/ 下生成mydemo-dev9节点.return 0;class_destroy(mydemo_dev_class);out_unreg_chrdev:unregister_chrdev(MYDEMO_MAJOR, "mydemo");out:printk(KERN_ERR "%s: Driver Initialisation failed\n", __FILE__);return res;}static void __exit mydemo_dev_exit(void){printk(KERN_INFO "my char dev demo out driver\n");class_destroy(mydemo_dev_class);unregister_chrdev(MYDEMO_MAJOR, "mydemo");}MODULE_AUTHOR("EastonWoo <[e-mail]>");MODULE_DESCRIPTION("my char dev demo entries driver");MODULE_LICENSE("GPL");module_init(mydemo_dev_init);module_exit(mydemo_dev_exit);

6. 修改drivers/Makefile:

添加obj-$(CONFIG_MY_DEMO)        += MyDemo/

7. 修改drivers/char/Kconfig:

添加source "drivers/MyDemo/Kconfig"

这样就完成了.可以编译测试了.