8.荔枝派 zero(全志V3S)-字符驱动
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1.驱动程序
#include
#include
#include
#include
#include
static int major = 232; /* 静态设备号方式的默认值 */
static int minor = 0; /* 静态设备号方式的默认值 */
module_param(major, int, S_IRUGO);
module_param(minor, int, S_IRUGO);
struct cdev *char_cdev; /* cdev 数据结构 */
static dev_t devno; /* 设备编号 */
static struct class *char_cdev_class;
#define DEVICE_NAME "char_cdev"
static int char_cdev_open(struct inode *inode, struct file *file )
{
try_module_get(THIS_MODULE);
printk(KERN_INFO DEVICE_NAME " opened!\n");
return 0;
}
static int char_cdev_release(struct inode *inode, struct file *file )
{
printk(KERN_INFO DEVICE_NAME " closed!\n");
module_put(THIS_MODULE);
return 0;
}
static ssize_t char_cdev_read(struct file *file, char *buf,size_t count, loff_t *f_pos)
{
printk(KERN_INFO DEVICE_NAME " read method!\n");
return count;
}
static ssize_t char_cdev_write(struct file *file, const char *buf, size_t count, loff_t *f_pos)
{
printk(KERN_INFO DEVICE_NAME " write method!\n");
return count;
}
static long char_cdev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
printk(KERN_INFO DEVICE_NAME " ioctl method!\n");
return 0;
}
struct file_operations char_cdev_fops = {
.owner = THIS_MODULE,
.read = char_cdev_read,
.write = char_cdev_write,
.open = char_cdev_open,
.release = char_cdev_release,
.unlocked_ioctl = char_cdev_ioctl
};
static int __init char_cdev_init(void)
{
int ret;
if (major > 0) { /* 静态设备号 */
devno = MKDEV(major, minor);
ret = register_chrdev_region(devno, 1, "char_cdev");
} else { /* 动态设备号 */
ret = alloc_chrdev_region(&devno, minor, 1, "char_cdev"); /* 从系统获取主设备号 */
major = MAJOR(devno);
}
if (ret < 0) {
printk(KERN_ERR "cannot get major %d \n", major);
return -1;
}
char_cdev = cdev_alloc(); /* 分配 char_cdev 结构 */
if (char_cdev != NULL) {
cdev_init(char_cdev, &char_cdev_fops); /* 初始化 char_cdev 结构 */
char_cdev->owner = THIS_MODULE;
if (cdev_add(char_cdev, devno, 1) != 0) { /* 增加 char_cdev 到系统中 */
printk(KERN_ERR "add cdev error!\n");
goto error;
}
} else {
printk(KERN_ERR "cdev_alloc error!\n");
return -1;
}
char_cdev_class = class_create(THIS_MODULE, "char_cdev_class");
if (IS_ERR(char_cdev_class)) {
printk(KERN_INFO "create class error\n");
return -1;
}
device_create(char_cdev_class, NULL, devno, NULL, "char_cdev" "%d", MINOR(devno));
printk(KERN_ERR "Init drive!\n");
return 0;
error:
unregister_chrdev_region(devno, 1); /* 释放已经获得的设备号 */
return ret;
}
static void __exit char_cdev_exit(void)
{
cdev_del(char_cdev); /* 移除字符设备 */
unregister_chrdev_region(devno, 1); /* 释放设备号 */
device_destroy(char_cdev_class, devno);
class_destroy(char_cdev_class);
printk(KERN_ERR "Exit drive!\n");
}
module_init(char_cdev_init);
module_exit(char_cdev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("JUN, [email protected]"); 2.驱动makefile
# Makefile
ifneq ($(KERNELRELEASE),)
#kbuild syntax. dependency relationshsip of files and target modules are listed here.
obj-m := char_dev.o
else
PWD:= $(shell pwd)
KDIR := /home/jun/v3s/linux-zero-4.10.y
all:
$(MAKE) -C $(KDIR) M=$(PWD) modules
clean:
rm -rf .*.cmd *.o *.mod.c *.ko .tmp_versions
endif3.测试程序
#include
#include
#include
#include
#include
#include
#define DEV_NAME "/dev/char_cdev0"
int main(int argc, char *argv[])
{
int i;
int fd = 0;
int dat = 0;
system("insmod char_cdev.ko");
system("mknod /dev/char_cdev c 200 0"); //create the file
fd = open (DEV_NAME, O_RDWR);
if (fd < 0) {
perror("Open "DEV_NAME" Failed!\n");
exit(1);
}
i = read(fd, &dat, 1);
if (!i) {
perror("read "DEV_NAME" Failed!\n");
exit(1);
}
dat = 0;
i = write(fd, &dat, 1);
if (!i) {
perror("write "DEV_NAME" Failed!\n");
exit(1);
}
ioctl(fd, 0);
close(fd);
return 0;
} 4.测试makefile
EXEC = ./bin/char_test
OBJS = char_test.o
CROSS = arm-linux-gnueabihf-
CC = $(CROSS)gcc
STRIP = $(CROSS)strip
CFLAGS = -Wall -g -O2
all: clean $(EXEC)
$(EXEC):$(OBJS)
$(CC) $(CFLAGS) -o $@ $(OBJS)
$(STRIP) $@
clean:
-rm -f $(EXEC) *.o5.测试
将驱动和测试程序编译出来
拷贝到设备
