Linux字符设备驱动编写和测试

 1 struct cdev{
 3 　　struct kobject kobj;
 5 　　struct module *owner;//所说模块
 7 　　struct file_operations *ops;//字符设备操作方法
 9 　　struct list_head list; 
11 　　dev_t dev;     //设备
13 　　unsigned int count;
15 }

1 void cdev_init(struct cdev *, struct file_operations *); //用于初始化cdev的成员，并建立cdev和file_operation之间的连接
2 struct cdev *cdev_alloc(void);//用于动态申请一个cdev内存
3 void cdev_put(struct cdev *p);
4 int cdev_add(struct cdev *, dev_t, unsigned);//向系统添加一个cdev，完成字符设备的注册，对cdev_add()的调用通常发生在字符设备驱动模块加载函数中
5 void cdev_del(struct cdev *);//删除一个cdev,完成字符设备的注销,对cdev_del()函数的调用则通常发生在字符设备驱动模块卸载函数中

1 int register_chrdev_region(dev_t from, unsigned count, const char *name); //已知起始设备号
2 int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,const char *name);//位置起始设备号

  1 #include <linux/module.h>
  2 #include <linux/fs.h>
  3 #include <linux/init.h>
  4 #include <linux/cdev.h>
  5 #include <linux/slab.h>
  6 #include <linux/uaccess.h>
  7 
  8 #define GLOBALMEM_SIZE 0x1000
  9 #define MEM_CLEAR 0x1
 10 #define GLOBALMEM_MAJOR 230
 11 
 12 static int globalmem_major = GLOBALMEM_MAJOR; //定义主设备号
 13 module_param(globalmem_major, int, S_IRUGO);//模块传参
 14 
 15 struct globalmem_dev {   //定义globalmen_dev结构体
 16  struct cdev cdev;//字符结构体
 17  unsigned char mem[GLOBALMEM_SIZE];//使用内存
 18 };
 19 
 20 struct globalmem_dev *globalmem_devp;//申明globalmem结构对象
 21 
 22 
 23 //globalmem设备驱动的读函数
 24 static ssize_t globalmem_read(struct file *filp, char __user * buf, size_t size,
 25  loff_t * ppos)
 26 {
 27  unsigned long p = *ppos;
 28  unsigned int count = size;
 29  int ret = 0;
 30  struct globalmem_dev *dev = filp->private_data;
 31 
 32  if (p >= GLOBALMEM_SIZE)
 33  return 0;
 34  if (count > GLOBALMEM_SIZE - p)
 35  count = GLOBALMEM_SIZE - p;
 36  if (copy_to_user(buf, dev->mem + p, count)) {
 37  ret = -EFAULT;
 38  } else {
 39  *ppos += count;
 40  ret = count;
 41  printk(KERN_INFO "read %u bytes(s) from %lu\n", count, p);
 42  }
 43  return ret;
 44 }
 45 //globalmem设备驱动的写函数
 46 static ssize_t globalmem_write(struct file *filp, const char __user * buf,
 47  size_t size, loff_t * ppos)
 48 {
 49  unsigned long p = *ppos;
 50  unsigned int count = size;
 51  int ret = 0;
 52  struct globalmem_dev *dev = filp->private_data;
 53 
 54 
 55  if (p >= GLOBALMEM_SIZE)
 56  return 0;
 57  if (count > GLOBALMEM_SIZE - p)
 58  count = GLOBALMEM_SIZE - p;
 59 
 60  if (copy_from_user(dev->mem + p, buf, count))
 61  ret = -EFAULT;
 62  else {
 63  *ppos += count;
 64  ret = count;
 65  
 66  printk(KERN_INFO "written %u bytes(s) from %lu\n", count, p);
 67  }
 68  return ret;
 69 }
 70 //寻址函数
 71 static loff_t globalmem_llseek(struct file *filp, loff_t offset, int orig)
 72 {
 73  loff_t ret = 0;
 74  switch (orig) {
 75  case 0: /* 从文件开头位置seek */
 76  if (offset< 0) {
 77  ret = -EINVAL;
 78  break;
 79  }
 80  if ((unsigned int)offset > GLOBALMEM_SIZE) {
 81  ret = -EINVAL;
 82  break;
 83  }
 84  filp->f_pos = (unsigned int)offset;
 85  ret = filp->f_pos;
 86  break;
 87  case 1: /* 从文件当前位置开始seek */
 88  if ((filp->f_pos + offset) > GLOBALMEM_SIZE) {
 89  ret = -EINVAL;
 90  break;
 91  }
 92  if ((filp->f_pos + offset) < 0) {
 93  ret = -EINVAL;
 94  break;
 95  }
 96  filp->f_pos += offset;
 97  ret = filp->f_pos;
 98  break;
 99  default:
100  ret = -EINVAL;
101  break;
102  }
103  return ret;
104 }
105 
106 static long globalmem_ioctl(struct file *filp, unsigned int cmd,
107  unsigned long arg)
108 {
109  struct globalmem_dev *dev = filp->private_data;
110  switch (cmd) {
111  case MEM_CLEAR:
112  memset(dev->mem, 0, GLOBALMEM_SIZE);
113  printk(KERN_INFO "globalmem is set to zero\n");
114  break;
115  default:
116  return -EINVAL;
117  }
118 
119  return 0;
120 }
121 //open函数
122 static int globalmem_open(struct inode *inode, struct file *filp)
123 {
124  filp->private_data = globalmem_devp;
125  return 0;
126 }
127 
128 //release函数
129 static int globalmem_release(struct inode *inode, struct file *filp)
130 {
131  return 0;
132 }
133 
134 /*定义字符结构体方法*/
135 static const struct file_operations globalmem_fops = {
136  .owner = THIS_MODULE,
137  .llseek = globalmem_llseek,
138  .read = globalmem_read,
139  .write = globalmem_write,
140  .unlocked_ioctl = globalmem_ioctl,
141  .open = globalmem_open,
142  .release = globalmem_release,
143 };
144 //字符设备加载函数
145 static void globalmem_setup_cdev(struct globalmem_dev *dev, int index)  
146 {
147  int err, devno = MKDEV(globalmem_major, index);//获取设备结构体dev_t
148 
149 
150  cdev_init(&dev->cdev, &globalmem_fops);//初始化字符设备和字符设备处理方法
151  dev->cdev.owner = THIS_MODULE;//初始化字符设备所属模块
152  err = cdev_add(&dev->cdev, devno, 1);//添加一个字符设备
153  if (err)
154  printk(KERN_NOTICE "Error %d adding globalmem%d", err, index);
155 
156 }
157 
158 
159 
160 //模块初始化
161 static int __init globalmem_init(void) //初始化模块
162 {
163  int ret;
164  dev_t devno = MKDEV(globalmem_major, 0);//获取字符设备结构体
165  if (globalmem_major)
166  ret = register_chrdev_region(devno, 1, "globalmem");//注册此cdev设备
167  else {
168  ret = alloc_chrdev_region(&devno, 0, 1, "globalmem");//申请字符设备cdev空间
169  globalmem_major = MAJOR(devno);//获取主设备号
170  }
171  if (ret < 0)
172  return ret;
173  globalmem_devp = kzalloc(sizeof(struct globalmem_dev), GFP_KERNEL);//分配globalmem结构体内存
174  if (!globalmem_devp) {
175  ret = -ENOMEM;
176  goto fail_malloc;    //分配失败择跳转
177  }
178 
179 //主次设备的不同
180  globalmem_setup_cdev(globalmem_devp, 0);
181  return 0;
182  fail_malloc:
183  unregister_chrdev_region(devno, 1);
184  return ret;
185 }
186 module_init(globalmem_init);
187 
188 
189 //模块卸载函数
190 static void __exit globalmem_exit(void)
191 {
192  cdev_del(&globalmem_devp->cdev);
193  kfree(globalmem_devp);
194  unregister_chrdev_region(MKDEV(globalmem_major, 0), 1);
195 }
196 module_exit(globalmem_exit);
197 
198 MODULE_AUTHOR("Barry Song <baohua@kernel.org>");
199 MODULE_LICENSE("GPL v2");

 1 KVERS = $(shell uname -r)
 2 # Kernel modules
 3 obj-m += globalmem.o
 4 
 5 # Specify flags for the module compilation.
 6 #EXTRA_CFLAGS=-g -O0
 7 build: kernel_modules
 8 kernel_modules:
 9     make -C /lib/modules/$(KVERS)/build M=$(CURDIR) modules
10 clean:
11     make -C /lib/modules/$(KVERS)/build M=$(CURDIR) clean

 1 #include<fcntl.h>
 2 #include<stdio.h>
 3 
 4 
 5 int main(void)
 6 {
 7     char s[] = "Linux Programmer!\n";
 8     char buffer[80];
 9     int fd=open("/dev/globalmem",O_RDWR);//打开globalmem设备，fd返回大于2的数则成功，O_RDWR为权限赋予
10     write(fd,s,sizeof(s));          //将字符串s写入globalmem字符设备中
11     printf("test write %d %s\n",fd,s );  
12         close(fd);  //关闭设备
13     fd=open("/dev/globalmem",O_RDWR);
14     read(fd,buffer,sizeof(buffer));   //读取globalmem设备中存储的数据
15     printf("test read %d %s\n",fd,buffer);  //输出结果显示
16     return 0;
17 
18 }