嵌入式：驱动开发 Day9

作业：通过platform总线驱动实现

a.应用程序通过阻塞的io模型来读取number变量的值
b.number是内核驱动中的一个变量
c.number的值随着按键按下而改变（按键中断）例如number=0 按下按键number=1 ,再次按下按键number=0
d.在按下按键的时候需要同时将led1的状态取反
e.驱动中需要编写字符设备驱动
f.驱动中需要自动创建设备节点
g.这个驱动需要的所有设备信息放在设备树的同一个节点中

驱动程序：my_platform.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/platform_device.h>
#include <linux/mod_devicetable.h>
#include <linux/of_gpio.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/interrupt.h>
#include <linux/wait.h>struct cdev *cdev;
unsigned int major = 0;
unsigned int minor = 0;
dev_t devno;
module_param(major, uint, 0664); //方便命令行传递major的值
struct class *cls;
struct device *dev;
struct resource *res;
unsigned int irqno;
struct gpio_desc *gpiono;
wait_queue_head_t wq_head; //定义一个等待队列头
unsigned int number = 0;
unsigned int condition = 0;//定义中断处理函数
irqreturn_t key_handler(int irq, void *dev)
{gpiod_set_value(gpiono, !gpiod_get_value(gpiono));if (number == 0){number = 1;condition = 1;wake_up_interruptible(&wq_head);}else{number = 0;condition = 1;wake_up_interruptible(&wq_head);}return IRQ_HANDLED;
}//封装操作方法
int mycdev_open(struct inode *inode, struct file *file)
{printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);return 0;
}ssize_t mycdev_read(struct file *file, char *ubuf, size_t size, loff_t *lof)
{int ret;//判断IO方式if (file->f_flags & O_NONBLOCK) //非阻塞{}else{                                                 //阻塞wait_event_interruptible(wq_head, condition); //先检查condition再将进程休眠}ret = copy_to_user(ubuf, &number, size);if (ret){printk("copy_to_user err\n");return -EIO;}condition = 0; //下一次硬件数据没有就绪return 0;
}ssize_t mycdev_write(struct file *file, const char *ubuf, size_t size, loff_t *lof)
{return 0;
}int mycdev_close(struct inode *inode, struct file *file)
{printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);return 0;
}//定义一个操作方法结构体对象并初始化
struct file_operations fops = {.open = mycdev_open,.read = mycdev_read,.write = mycdev_write,.release = mycdev_close,
};//封装probe函数
int pdrv_probe(struct platform_device *pdev)
{//初始化等待队列init_waitqueue_head(&wq_head);int ret;//1.为字符设备驱动对象申请空间cdev = cdev_alloc();if (cdev == NULL){printk("申请字符设备驱动对象空间失败\n");ret = -EFAULT;goto out1;}printk("申请字符设备驱动对象空间成功\n");//2.初始化字符设备驱动对象cdev_init(cdev, &fops);printk("初始化字符设备驱动对象成功\n");//3.申请设备号if (major > 0) //静态指定设备号{ret = register_chrdev_region(MKDEV(major, minor), 3, "myled");if (ret){printk("静态申请设备号失败\n");goto out2;}}else if (major == 0){ //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); //获取主设备号minor = MINOR(devno); //获取次设备号}printk("申请设备号成功\n");//4.注册字符设备驱动对象ret = cdev_add(cdev, MKDEV(major, minor), 3);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");//向上提交目录信息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");//向上提交设备节点信息int i;for (i = 0; i < 3; i++){dev = device_create(cls, NULL, MKDEV(major, i), NULL, "myled%d", i);if (IS_ERR(dev)){printk("向上提交设备节点信息失败\n");ret = -PTR_ERR(dev);goto out5;}}printk("向上提交设备信息成功\n");//platform//获取MEM类型的资源res = platform_get_resource(pdev, IORESOURCE_MEM, 0);if (res == NULL){printk("获取MEM类型资源失败\n");return -ENXIO;}//获取中断类型的资源irqno = platform_get_irq(pdev, 0);if (irqno < 0){printk("获取中断类型资源失败\n");return -ENXIO;}//设备树匹配成功后，设备树结点指针可以通过pdev->dev.of_node获取//基于设备树节点信息获取gpio_desc对象指针gpiono = gpiod_get_from_of_node(pdev->dev.of_node, "led1-gpio", 0, GPIOD_OUT_LOW, NULL);if (IS_ERR(gpiono)){printk("解析GPIO管脚信息失败\n");return -ENXIO;}printk("解析GPIO管脚信息成功\n");//注册按键中断ret = request_irq(irqno, key_handler, IRQF_TRIGGER_FALLING, "key_init", NULL);if (ret < 0){printk("注册按键%d中断失败\n", i);return ret;}printk("注册按键中断成功\n");return 0;out5://释放前一次提交成功的设备信息for (--i; i >= 0; i--){device_destroy(cls, MKDEV(major, i));}class_destroy(cls); //释放目录
out4://注销字符设备驱动对象cdev_del(cdev);
out3://释放设备号unregister_chrdev_region(MKDEV(major, minor), 3);
out2://释放设备驱动对象空间kfree(cdev);
out1:return ret;
}//封装remove函数
int pdrv_remove(struct platform_device *pdev)
{//注销中断free_irq(irqno, NULL);//释放GPIO信息gpiod_put(gpiono);int i;//释放设备节点信息for (i = 0; i < 3; i++){device_destroy(cls, MKDEV(major, i));}//销毁目录class_destroy(cls);//注销字符设备驱动对象cdev_del(cdev);//释放设备号unregister_chrdev_region(MKDEV(major, minor), 3);//释放设备驱动对象空间kfree(cdev);return 0;
}//构建设备树匹配表
struct of_device_id oftable[] = {{.compatible = "hqyj,myplatform"},{}, //防止数组越界
};//定义platform驱动信息对象并初始化
struct platform_driver pdrv = {.probe = pdrv_probe,.remove = pdrv_remove,.driver = {.name = "bbbbb",.of_match_table = oftable, //用于设备树匹配},
};//一键注册platform宏
module_platform_driver(pdrv);
MODULE_LICENSE("GPL");

应用程序：test.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
int main(){unsigned int number;int fd = open("/dev/myled0", O_RDWR);if(fd < 0){printf("设备文件打开失败\n");exit(-1);}while(1){read(fd, &number, sizeof(number));printf("number = %d\n", number);}close(fd);return 0;
}