编写LED灯的驱动，创建三个设备文件，每个设备文件和一个LED灯绑定，当操作这个设备文件时只能控制设备文件对应的这盏灯。文章来源地址https://www.toymoban.com/news/detail-545255.html
- 完整目录，查看这个仓库
- 注册设备驱动对象
cdev_add也需要对三个 LED 分别添加，否则LED2和LED3的设备文件虽然生成，但是无法被用户空间打开
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/uacce.h>
#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/io.h>
#include "head.h"
struct cdev *cdev;
unsigned int major = 0; // 自动分配主设备号
unsigned int minor = 0; // 次设备号的起始值
dev_t devno;
struct class *cls;
struct device *dev;
gpio_t *vir_gpioe;
gpio_t *vir_gpiof;
rcc_t *vir_rcc;
int all_led_init(void)
{
// 地址映射
vir_gpioe = (gpio_t *)ioremap((unsigned int)GPIOE, sizeof(gpio_t));
if (vir_gpioe == NULL) {
printk("GPIOE地址映射失败\n");
return -1;
}
vir_gpiof = (gpio_t *)ioremap((unsigned int)GPIOF, sizeof(gpio_t));
if (vir_gpiof == NULL) {
printk("GPIOF地址映射失败\n");
return -1;
}
vir_rcc = (rcc_t *)ioremap((unsigned int)RCC, sizeof(rcc_t));
if (vir_rcc == NULL) {
printk("RCC地址映射失败\n");
return -1;
}
// 寄存器初始化
vir_rcc->MP_AHB4ENSETR |= (1 << 4) | (1 << 5); // 使能GPIOE和GPIOF时钟
// LED1
vir_gpioe->MODER &= (~(0x3 << 20));
vir_gpioe->MODER |= (0x1 << 20); // 设置PE10为输出模式
vir_gpioe->ODR &= (~(1 << 10)); // 默认PE10输出低电平
// LED2
vir_gpiof->MODER &= (~(0x3 << 20));
vir_gpiof->MODER |= (0x1 << 20); // 设置PF10为输出模式
vir_gpiof->ODR &= (~(1 << 10)); // 默认PF10输出低电平
// LED3
vir_gpioe->MODER &= (~(0x3 << 16));
vir_gpioe->MODER |= (0x1 << 16); // 设置PE8为输出模式
vir_gpioe->ODR &= (~(1 << 8)); // 默认PE8输出低电平
return 0;
}
int mycdev_open(struct inode *inode, struct file *file)
{
unsigned int aaa = MINOR(inode->i_rdev); // 得到次设备号
file->private_data = (void *)aaa; // 将次设备号保存到file->private_data
printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);
return 0;
}
long mycdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
unsigned int _minor = (unsigned int)file->private_data;
switch (_minor) {
case 0: // 对应 LED1
switch (cmd) {
case LED_ON:
vir_gpioe->ODR |= (1 << 10);
break;
case LED_OFF:
vir_gpioe->ODR &= ~(1 << 10);
break;
}
break;
case 1: // 对应 LED2
switch (cmd) {
case LED_ON:
vir_gpiof->ODR |= (1 << 10);
break;
case LED_OFF:
vir_gpiof->ODR &= ~(1 << 10);
break;
}
break;
case 2: // 对应 LED3
switch (cmd) {
case LED_ON:
vir_gpioe->ODR |= (1 << 8);
break;
case LED_OFF:
vir_gpioe->ODR &= ~(1 << 8);
break;
}
break;
}
return 0;
}
int mycdev_close(struct inode *inode, struct file *file)
{
printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);
return 0;
}
struct file_operations fops = {
.open = mycdev_open,
.unlocked_ioctl = mycdev_ioctl,
.release = mycdev_close,
};
static int __init mycdev_init(void)
{
int ret, i;
//1.分配字符设备驱动对象空间 cdev_alloc
cdev = cdev_alloc();
if (cdev == NULL) {
printk("字符设备驱动对象申请空间失败\n");
return -EFAULT;
goto out1;
}
printk("字符设备驱动对象申请空间成功\n");
//2.字符设备驱动对象部分初始化 cdev_init
cdev_init(cdev, &fops);
//3.申请设备号 register_chrdev_region/alloc_chrdev_region
if (major > 0) { // 静态指定设备号
ret = register_chrdev_region(MKDEV(major, minor), 3, "myled");
if (ret) {
printk("静态指定设备号失败\n");
goto out2;
}
} else { // 动态申请设备号
ret = alloc_chrdev_region(&devno, minor, 3, "myled");
if (ret) {
printk("动态申请设备号失败\n");
goto out2;
}
major = MAJOR(devno); // 根据设备号获取主设备号
minor = MINOR(devno); // 根据设备号获取次设备号
}
printk("申请设备号成功——主设备号:%d, 次设备号:%d\n", major, minor);
//4.注册字符设备驱动对象 cdev_add()
for (i = 0; i < 3; i++) {
ret = cdev_add(cdev, MKDEV(major, minor + i), 1);
if (ret) {
printk("注册字符设备驱动对象失败\n");
goto out3;
}
}
printk("注册字符设备驱动对象成功\n");
//5.向上提交目录
cls = class_create(THIS_MODULE, "myled");
if (IS_ERR(cls)) {
printk("向上提交目录失败\n");
ret = -PTR_ERR(cls);
goto out4;
}
printk("向上提交目录成功\n");
//6.向上提交设备节点
for (i = 0; i < 3; i++) {
dev = device_create(cls, NULL, MKDEV(major, minor + i), NULL,
"myled%d", i);
if (IS_ERR(dev)) {
printk("向上提交设备节点失败\n");
ret = -PTR_ERR(dev);
goto out5;
}
}
printk("向上提交设备节点成功\n");
all_led_init();
return 0;
out5:
for (--i; i >= 0; i--) { // 从失败的位置开始回退
device_destroy(cls, MKDEV(major, minor + i));
}
class_destroy(cls);
out4:
cdev_del(cdev);
out3:
unregister_chrdev_region(MKDEV(major, minor), 3);
out2:
kfree(cdev);
out1:
return ret;
}
static void __exit mycdev_exit(void)
{
//1.销毁设备信息 device_destroy
int i;
for (i = 0; i < 3; i++)
device_destroy(cls, MKDEV(major, minor + i));
//2.销毁目录 class_destroy
class_destroy(cls);
//3.注销对象 cdev_del()
cdev_del(cdev);
//4.释放设备号 unregister_chrdev_region()
unregister_chrdev_region(MKDEV(major, minor), 3);
//5.释放对象空间 kfree()
kfree(cdev);
}
module_init(mycdev_init);
module_exit(mycdev_exit);
MODULE_LICENSE("GPL");
文章来源：https://www.toymoban.com/news/detail-545255.html
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