忘記很早以前從哪裡的找到的一個很簡單的C代碼,完成了字元裝置註冊,自動擷取裝置號(主/從),並且自動建立裝置節點。
由於最近好幾個人問我類似的問題,因此在這裡貼出了,供大家參考。
感謝代碼的原作者:zengxiaolong
以下代碼在2..6.35-22核心下編譯通過。
create_chrdev.c:
// create_chrdev.c
// ---------------------------------------------
#include <linux/types.h> //dev_t
#include <linux/cdev.h> //struct cdev
#include <linux/fs.h> //alloc_chrdev_region()
#include <linux/device.h> //class_create()
dev_t devid;
static struct cdev *led_cdev;
static int led_Major = 0;
static int led_Minor = 0;
static struct class *led_class;
static struct file_operations led_fops = {
.owner = THIS_MODULE,
};
static int __init hello_init(void)
{
int err;
//初始化cdev
led_cdev = cdev_alloc();
cdev_init(led_cdev, &led_fops);
led_cdev->owner = THIS_MODULE;
//動態擷取主裝置號(dev_t devid中包含"主裝置號"和"次裝置號"資訊)
alloc_chrdev_region(&devid, 66, 1, "led");//從66開始分配1個裝置號
led_Major = MAJOR(devid);
led_Minor = MINOR(devid);
printk(KERN_INFO "I was assigned major number %d.\n", led_Major);
printk(KERN_INFO "I was assigned minor number %d.\n", led_Minor);
//註冊字元裝置 (1)
err = cdev_add(led_cdev, devid, 1);
if (err) {
printk(KERN_NOTICE "Error %d adding device\n", err);
return -1;
}
led_class = class_create(THIS_MODULE, "led_class1");//在/sys目錄下建立了一個一個led_class1的目錄
if (IS_ERR(led_class)) {
printk(KERN_INFO "create class error\n");
return -1;
}
device_create(led_class,NULL,devid,NULL,"led" "%d", MINOR(devid));
//在2.6早期的版本應該使用class_device_create,早於2.6.27? 2.6.29? 忘記了。這一步在/dev目錄下建立了一個led66的裝置檔案
return 0;
}
static void __exit hello_exit(void)
{
unregister_chrdev_region(devid, 1);
cdev_del(led_cdev);
device_destroy(led_class, devid);//在2.6早期的版本應該使用class_device_destroy,早於2.6.27? 2.6.29? 忘記了。
class_destroy(led_class);
}
module_init(hello_init);
module_exit(hello_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("zengxiaolong ");
MODULE_DESCRIPTION("A sample driver");
MODULE_SUPPORTED_DEVICE("testdevice");
Makefile(for PC):
obj-m := create_chrdev.o
KERNELDIR :=/lib/modules/$(shell uname -r)/build
default:
make -C $(KERNELDIR) M=$(shell pwd) modules
install:
insmod create_chrdev.ko
uninstall:
rmmod create_chrdev
clean:
make -C $(KERNELDIR) M=$(shell pwd) clean
Makefile(for ARM):
obj-m := create_chrdev.o
KERNELDIR := /usr/local/src/ARM2440/kernel-2.6.29 #it is your arm kernel folder
default:
make -C $(KERNELDIR) M=$(shell pwd) modules
install:
insmod create_chrdev.ko
uninstall:
rmmod create_chrdev
clean:
make -C $(KERNELDIR) M=$(shell pwd) clean