自动创建字符设备，不需mknod
自动创建设备文件
1.自动创建设备文件的流程
字符设备驱动模块 --》创建一个设备驱动class--->创建属于class的device--->调用mdev工具(自动完成)--> 生成设备文件
mdev工具会根据/sys下的class找到相对应的device，然后根据device创建设备文件
class /sys/class
device /sys/device
1.1创建class /注销class
struct class * class_create(struct module *owner,const char *name);
参数:
struct module *owner---> class属于哪些一个module --->THIS_MODULE
const char *name --->自定义的类名.
返回值:
NULL -->失败
void class_destroy(struct class * cls)
例:
struct class *led_class=class_create(THIS_MODULE,"led_class");
class_destroy(led_class)
1.2创建device /注销
struct device *device_create(struct class *class, struct device *parent,
dev_t devt, void *drvdata, const char *fmt, ...)
参数:
struct class *class --->当前device属于那个class
struct device *parent --->device的parent,一般为NULL
dev_t devt --->设备号
void *drvdata --->设备的私有数据，一般为NULL
const char *fmt ---》 device的名字，也就是设备文件名
返回值:
struct device *
NULL -->失败
void device_destroy(struct class * class,dev_t devt);
struct device *dp=device_create(led_class,NULL,dev_no,NULL,"led_drv") ---> /dev/led_drv (字符设备)
if(dp==NULL)
{
}
1 #include<linux/module.h> 2 #include<linux/kernel.h> 3 #include<linux/cdev.h> 4 #include<linux/fs.h> 5 #include<linux/kdev_t.h> 6 #include<linux/types.h> 7 #include<linux/uaccess.h> 8 #include<linux/string.h> 9 #include<linux/ioport.h> 10 #include<asm/io.h> 11 #include<linux/init.h> 12 #include<linux/device.h> 13 #define GPJ2CON_PA 0xe0200280 14 #define GPJ2DAT_PA 0xe0200280 15 unsigned int *GPJ2CON_VA; 16 unsigned int *GPJ2DAT_VA; 17 struct cdev chrdev; 18 struct resource *res; 19 struct class *cla; 20 struct device *dev; 21 unsigned int TestMajor=0; 22 unsigned int TestMinor=0; 23 dev_t dev_no; 24 int ret; 25 26 int testopen(struct inode *inode,struct file *file) 27 { 28 unsigned int a = ioread32(GPJ2CON_VA); 29 a |= 0x1111; 30 iowrite32(a,GPJ2CON_VA); 31 printk("cdev init\n"); 32 return 0; 33 34 } 35 ssize_t testwrite(struct file *file, const char __user *usr, size_t len, loff_t *off) 36 { 37 unsigned int a; 38 39 copy_from_user(&a,usr,len); 40 iowrite32(a,GPJ2DAT_VA); 41 42 43 } 44 ssize_t testread(struct file *file, char __user *usr, size_t len, loff_t *off) 45 { 46 unsigned int a = ioread32(GPJ2DAT_VA); 47 copy_to_user(usr,&a,len); 48 49 50 } 51 int testrelease(struct inode *inode, struct file *file) 52 { 53 printk("close\n"); 54 return 0; 55 56 } 57 58 struct file_operations fops= 59 { 60 .owner=THIS_MODULE, 61 .open = testopen, 62 .write = testwrite, 63 .read = testread, 64 .release = testrelease, 65 }; 66 static int __init test_init(void) 67 { 68 dev_no = MKDEV(TestMajor,TestMinor); 69 if(dev_no>0) 70 { 71 ret = register_chrdev_region(dev_no,1,"chrdev_test"); 72 } 73 else 74 { 75 alloc_chrdev_region(&dev_no,0,1,"chrdev_test"); 76 } 77 if(ret<0) 78 { 79 return ret; 80 } 81 cdev_init(&chrdev,&fops); 82 chrdev.owner=THIS_MODULE; 83 cdev_add(&chrdev,dev_no,1); 84 res = request_mem_region(GPJ2CON_PA,8,"gpj2_led"); 85 GPJ2CON_VA = ioremap(GPJ2CON_PA,8); 86 GPJ2DAT_VA = GPJ2CON_VA + 1; 87 cla = class_create(THIS_MODULE,"led_class"); 88 if(cla == NULL) 89 { 90 printk("class_creat() error!\n"); 91 } 92 dev = device_create(cla,NULL,dev_no,NULL,"chrdev_test"); 93 if(dev == NULL) 94 { 95 printk("device_creat() error!\n"); 96 } 97 98 return 0; 99 } 100 101 static int __exit test_exit(void) 102 { 103 unregister_chrdev_region(dev_no,1); 104 cdev_del(&chrdev); 105 iounmap(GPJ2CON_VA); 106 release_mem_region(GPJ2CON_PA,8); 107 device_destroy(cla,dev_no); 108 class_destroy(cla); 109 return 0; 110 } 111 112 module_init(test_init); 113 module_exit(test_exit); 114 115 116 MODULE_AUTHOR("FENG"); 117 MODULE_DESCRIPTION("the first module of char drivers"); 118 MODULE_LICENSE("GPL"); 119 MODULE_VERSION("V1.0");
