Linux学习 :字符设备框架
一.系统功能框架:
U-boot : 启动内核
linux kernel: 启动应用
应用: open,read,write 都是通过C库实现,汇编就相当于swi val,引发中断,通过系统调用接口在异常中断调用不同处理函数(VFS)。
二.字符设备驱动框架:
1.编写驱动:open , read, write 等功能函数的实现:
static int led_drv_open(struct inode *inode, struct file *file){
printk("led_drv_open\n");
return 0;
}
static int led_drv_write(struct file *file, const char __user *buf, size_t count, loff_t* ppos){
printk("led_drv_write\n");
return 0;
}
2.注册驱动:
①构造file_operations结构:
static struct file_operation led_drv_fops = {
.owner = THIS_MODULE,
.open = led_drv_open,
.write = led_drv_write,
}
②注册驱动:
入口函数:
int major;
int led_drv_init(void){
major = register_chrdev(0, "led_drv", &led_drv_fops); //注册字符设备,major-主设备号 mior-次设备号,app根据设备类型和主设备号调用具体驱动。
//创建设备节点:
//... class_create(THIS_MODULE, "led_drv");
//... clase_device_create(...);
return 0;
}
修饰入口函数: module_init(led_drv_init);
出口函数:void led_drv_exit(void){
unregister_chrdev(major, "led_drv");
}
修饰出口函数: module_exit(led_drv_exit);
③编译:
Makefile :
KERN_DIR=/work/system/linux-2.6.22.6 //本地编译过的linux源码目录
all:
make -C $(KERN_DIR) M=`pwd` modules
clean:
make -C $(KERN_DIR) M=`pwd` modules clean
rm -rf modules.order
obj-m += led_drv.o
④加载:
insmod led_drv.ko
cat /proc/devices
三.參考代碼:
驱动程序:first_drv.c
#include <linux/module.h> #include <linux/kernel.h> #include <linux/fs.h> #include <linux/init.h> #include <linux/delay.h> #include <asm/uaccess.h> #include <asm/irq.h> #include <asm/io.h> #include <asm/arch/regs-gpio.h> #include <asm/hardware.h> static struct class *firstdrv_class; static struct class_device *firstdrv_class_dev; volatile unsigned long *gpfcon = NULL; volatile unsigned long *gpfdat = NULL; static int first_drv_open(struct inode *inode, struct file *file) { //printk("first_drv_open\n"); /* 配置GPF4,5,6为输出 */ *gpfcon &= ~((0x3<<(4*2)) | (0x3<<(5*2)) | (0x3<<(6*2))); *gpfcon |= ((0x1<<(4*2)) | (0x1<<(5*2)) | (0x1<<(6*2))); return 0; } static ssize_t first_drv_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos) { int val; //printk("first_drv_write\n"); copy_from_user(&val, buf, count); // copy_to_user(); if (val == 1) { // 点灯 *gpfdat &= ~((1<<4) | (1<<5) | (1<<6)); } else { // 灭灯 *gpfdat |= (1<<4) | (1<<5) | (1<<6); } return 0; } static struct file_operations first_drv_fops = { .owner = THIS_MODULE, /* 这是一个宏,推向编译模块时自动创建的__this_module变量 */ .open = first_drv_open, .write = first_drv_write, }; int major; static int first_drv_init(void) { major = register_chrdev(0, "first_drv", &first_drv_fops); // 注册, 告诉内核 firstdrv_class = class_create(THIS_MODULE, "firstdrv"); firstdrv_class_dev = class_device_create(firstdrv_class, NULL, MKDEV(major, 0), NULL, "xyz"); /* /dev/xyz */ gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16); gpfdat = gpfcon + 1; return 0; } static void first_drv_exit(void) { unregister_chrdev(major, "first_drv"); // 卸载 class_device_unregister(firstdrv_class_dev); class_destroy(firstdrv_class); iounmap(gpfcon); } module_init(first_drv_init); module_exit(first_drv_exit); MODULE_LICENSE("GPL");
测试程序:firstdrvtest.c
#include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <stdio.h> /* firstdrvtest on * firstdrvtest off */ int main(int argc, char **argv) { int fd; int val = 1; fd = open("/dev/xyz", O_RDWR); if (fd < 0) { printf("can't open!\n"); } if (argc != 2) { printf("Usage :\n"); printf("%s <on|off>\n", argv[0]); return 0; } if (strcmp(argv[1], "on") == 0) { val = 1; } else { val = 0; } write(fd, &val, 4); return 0; }
Makefile:
KERN_DIR = /work/system/linux-2.6.22.6 all: make -C $(KERN_DIR) M=`pwd` modules clean: make -C $(KERN_DIR) M=`pwd` modules clean rm -rf modules.order obj-m += first_drv.o
posted on 2016-09-12 17:42 sheldon_blogs 阅读(502) 评论(0) 编辑 收藏 举报