linux驱动——dht11温湿度传感器驱动（5.4版本内核）

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/mutex.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/kmod.h>
#include <linux/gfp.h>
#include <asm/mach/map.h>
#include <linux/platform_device.h>
#include <asm/io.h>
#include <linux/mod_devicetable.h>
#include <linux/gpio.h>
#include <linux/delay.h>
#include <linux/timekeeping.h>


static struct cdev dht11_cdev;
static struct class *dht11_class;
struct gpio_desc * dht11_gpio_desc;
static int major;

static unsigned char g_us[40];

static void dht11_reset(void)
{
    gpiod_direction_output(dht11_gpio_desc, 1);
}

// 注意！！！！！！
static void dht11_start(void)
{
    // 不能使用GPIOD_OUT_HIGH，有问题，字节用0,1
    mdelay(30);
    gpiod_set_value(dht11_gpio_desc, 0);
    mdelay(20);
    gpiod_set_value(dht11_gpio_desc, 1);
    udelay(40);
    gpiod_direction_input(dht11_gpio_desc);
    udelay(2);
}

static int dht11_wait_ready(void)
{
    int timeout_us = 20000;
    
    /*  等待低电平   */
    timeout_us = 200;
    while(gpiod_get_value(dht11_gpio_desc) && --timeout_us) {
        udelay(1);
    }
    // 超时
    if (!timeout_us) {
        printk("----debug1-----\n");
        return -1;
    }

    /* 等待高电平    */
    timeout_us = 200;
    while(!gpiod_get_value(dht11_gpio_desc) && --timeout_us) {
        udelay(1);
    }
    if (!timeout_us) {
        printk("----debug2-----\n");
        return -1;
    }
    /*  等待低电平   */
    timeout_us = 200;
    while(gpiod_get_value(dht11_gpio_desc) && --timeout_us) {
        udelay(1);
    }
    // 超时
    if (!timeout_us) {
        printk("----debug3-----\n");
        return -1;
    }

    return 0;
}

static int dht11_read_byte(unsigned char *data)
{
    int i = 0;
    unsigned char buffer;
    int timeout_us = 400;
    int high_us = 0;
    for (i=0;i<8;i++) {

        /* 等待高电平    */
        timeout_us = 400;
        while(!gpiod_get_value(dht11_gpio_desc) && --timeout_us) {
            udelay(1);
        }
        if (!timeout_us) {
            return -1;
        }
        
        udelay(40);
        
        if (gpiod_get_value(dht11_gpio_desc)) {
            buffer = (buffer << 1) | 1;

            /*  等待高电平结束 */
            timeout_us = 400;
            while(gpiod_get_value(dht11_gpio_desc) && --timeout_us) {
                udelay(1);
            }
            if (!timeout_us) {
                return -1;
            }
        } else {
            buffer = (buffer << 1) | 0;
        }
    }

    *data = buffer;
    return 0;
}

/* 写法与协议有关 */
static ssize_t dht11_drv_read(struct file * file, char __user * buf, size_t size, loff_t *offset)
{
    int i = 0;
    unsigned long flags;
    unsigned char kernel_buf[5];
    u64 pre,last;

    if (size !=4 ) {
        return -EINVAL;
    }

    local_irq_save(flags);

    pre = ktime_get_boottime_ns();
    //for(i=0;i<1000;i++)
    //  udelay(1);
    udelay(40);
    last = ktime_get_boottime_ns();

    printk("udelay 1000 times use ns: %lld\n", last-pre);
    
    // 1. 发送高脉冲启动DHT11
    dht11_reset();
    dht11_start();

    // 2. 等待DHT11就绪
    if (0 != dht11_wait_ready()) {
        printk("设备未就绪\n");
        local_irq_restore(flags);
        return -1;
    }

    // 3. 读取5个字节
    for (i=0;i<5;i++) {
        if (dht11_read_byte(&kernel_buf[i]) != 0) {
            local_irq_restore(flags);
            return -1;
        }
    }
    dht11_reset();
    
    local_irq_restore(flags);

    // 4. 根据检验码验证数据
    if (kernel_buf[4] != kernel_buf[0] + kernel_buf[1] + kernel_buf[2] + kernel_buf[3]) {
        printk("验证错误\n");
        local_irq_restore(flags);
        return -1;
    }

    // 5. 返回给用户
    size = copy_to_user(buf, kernel_buf, size);

    return size;
}

static ssize_t dht11_drv_write(struct file *file, const char __user *buf, size_t size, loff_t *offset)
{

    return 0;
}

static int dht11_drv_open(struct inode *node, struct file *file)
{

    return 0;
}
static int dht11_drv_close(struct inode *node, struct file *file)
{

    return 0;
}
static struct file_operations dht11_opr = {
    .open = dht11_drv_open,
    .release = dht11_drv_close,
    .read = dht11_drv_read,
    .write = dht11_drv_write,
};

static int dht11_probe(struct platform_device *pdev)
{
    int err;
    dev_t devid;
    printk("====%s====\n", __FUNCTION__);
    // 从设备树获取资源
    dht11_gpio_desc = gpiod_get(&pdev->dev, NULL, GPIOD_OUT_HIGH);
    //dht11_data_pin = gpiod_get(&pdev->dev, NULL, GPIOD_OUT_HIGH);
    if (IS_ERR(dht11_gpio_desc))    {
        printk("get gpiod_desc error");
        return -1;
    }
    
    // 设置/注册cdev
    err = alloc_chrdev_region(&devid, 0, 1, "dht11");
    major = MAJOR(devid);
    cdev_init(&dht11_cdev, &dht11_opr);
    cdev_add(&dht11_cdev, devid, 1);

    // 建立class
    dht11_class = class_create(THIS_MODULE, "dht11_class");
    // 建立device
    device_create(dht11_class, NULL, MKDEV(major, 0), NULL, "dht11"); // 创建节点/dev/dht11

    return 0;
}

static int dht11_remove(struct platform_device *pdev)
{
    // 释放class,device
    printk("======%s=======\n", __FUNCTION__);
    
    device_destroy(dht11_class, MKDEV(major, 0));
    class_destroy(dht11_class);
    unregister_chrdev(major, "dht11");
    gpiod_put(dht11_gpio_desc);
    return 0;
}

static const struct of_device_id dht11_match[] = {
    { .compatible = "fire,dht11" },
    { },
};

struct platform_driver dht11_driver = {
    .probe = dht11_probe,
    .remove = dht11_remove,
    .driver = {
        .name = "my_dht11_driver",
        .of_match_table = dht11_match,
    },
};

// 入口函数
static int dht11_platform_driver_init(void)
{
    int ret = 0;
    printk("====%s====\n", __FUNCTION__);
    ret = platform_driver_register(&dht11_driver);  // 注册设备信息
    return ret;
}

// 出口函数
static void dht11_platform_driver_exit(void)
{
    printk("====%s====\n", __FUNCTION__);
    platform_driver_unregister(&dht11_driver);  // 注册设备信息
}

module_init(dht11_platform_driver_init);
module_exit(dht11_platform_driver_exit);
MODULE_LICENSE("GPL");

dht11:fire_dht11 {
    compatible = "fire,dht11";
    gpios = <&gpio4 28 GPIO_ACTIVE_HIGH>;   // 填写你使用的引脚
};

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

int main(int argn, char **argv)
{
    int fd;
    int ret = 0;
    unsigned char data[4];
    if (argn !=2) {
        printf("Usage: %s /dev/xxx\n", argv[0]);
        return -1;
    }

    fd = open(argv[1], O_RDONLY);
    if (fd < 0) {
        perror("open error");
        return -1;
    }

    while(1) {
        ret = read(fd, data, 4);
        if (ret < 0) {
            perror("read error");
            return -1;
        }
        printf("temperature: %d.%d\t", data[0], data[1]);
        printf("humidity: %d.%d\n", data[2], data[3]);
        
        sleep(1);
    }
}

# 指定架构
ARCH=arm
# 指定编译工具链
CROSS_COMPILE=arm-linux-gnueabihf-
export  ARCH  CROSS_COMPILE

# 指定内核根目录，需要和板子上运行的驱动一致
KERN_DIR = /home/hxd/linux_kernel/kernel_5.4

name=dht11

all:
    make -C $(KERN_DIR) M=`pwd` modules 
    $(CROSS_COMPILE)gcc -o $(name)_test $(name)_test.c 

clean:
    make -C $(KERN_DIR) M=`pwd` modules clean
    rm -rf modules.order
    rm -f $(name)_test

obj-m   += $(name)_drv.o

#include <linux/timekeeping.h>

u64 pre,last;
pre = ktime_get_boottime_ns();
// 测试代码
for(i=0;i<1000;i++)
    udelay(40);
last = ktime_get_boottime_ns();

printk("udelay 1000 times use ns: %lld\n", last-pre);