[Linux下menuconfig與Kconfig基礎知識概要](https://www.cnblogs.com/chorm590/p/13977818.html)
[編譯器](https://hackmd.io/@ofAlpaca/ryNNXAuoQ/https%3A%2F%2Fhackmd.io%2Fs%2FB1aGFRW6Q?type=book)
[Android makefile 變數名稱定義](https://www.cnblogs.com/chenbin7/archive/2013/01/05/2846863.html)
[Linux 基本觀念](https://dywang.csie.cyut.edu.tw/dywang/linuxSystem/linuxSystem.html)
[HAL - 硬體驅動](https://hackmd.io/@AlienHackMd/B1rTpFrxi)
[Android編譯系統](https://hackmd.io/@AlienHackMd/SJ_1iUIw_#Android-%E7%B7%A8%E8%AD%AF%E7%B3%BB%E7%B5%B11)
[跟我一起寫makefile PDF版](https://seisman.github.io/how-to-write-makefile/Makefile.pdf)
[跟我一起寫makefile 網頁版](https://seisman.github.io/how-to-write-makefile/introduction.html)
[【小常識】從按鈕開關看上拉pull-up電阻下拉電阻是蝦密碗糕](https://www.arduino.cn/thread-13186-1-1.html)
[探討Designated Initializers](https://meetonfriday.com/posts/39485259/)

之後有空可以玩玩看 -> [可编程像素屏](https://www.youtube.com/watch?v=ExfKmG-m1SY)

---

[溫濕度datasheet](https://cdn-shop.adafruit.com/datasheets/DHT11-chinese.pdf)

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/input.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/serio.h>
#include <linux/delay.h>
#include <linux/clk.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/cdev.h>
#include <linux/miscdevice.h>
#include <linux/gpio.h>
#include <mach/gpio.h>
#include <asm-generic/uaccess.h>
#include <linux/spinlock.h>

#define DEVICE_MAJOR 232
#define DEVICE_NAME "dht11"
#define PIN	EXYNOS4_GPX0(6)

typedef unsigned char  U8;
unsigned char buf[6];
//DEFINE_SPINLOCK(lock);
unsigned char check_flag;

int data_in(void)
{
	gpio_direction_input(PIN);
	return gpio_get_value(PIN);
}
void gpio_out(int value)   //set gpio is output
{
    gpio_direction_output(PIN,value);
}

void humidity_read_data(void)
{
	int i=0,j=0;
	int num; 
    unsigned char flag=0;
	unsigned char data=0;
	gpio_out(0);
	mdelay(30);
	gpio_out(1);
	udelay(40);    
	if(data_in() == 0)
	{ 
		while(!gpio_get_value(PIN))
		{
			udelay(5);
			i++;
			if(i>20)
			{
				printk("error data!\n");
				break;
        	}
		}
		i=0;
		while(gpio_get_value(PIN))
		{
        	udelay(5);
        	i++;
        	if(i>20)
        	{
				printk("error data!\n");
				break;
			}
		}
	}
	for(i = 0;i < 5;i++)
	{
		for(num = 0;num < 8;num++)
		{              
			j = 0;
			while( !gpio_get_value(PIN) )
			{
				udelay(10);
				j++;
				if(j > 40)
				break;
			}
			flag = 0x0;
			udelay(28);
			if( gpio_get_value(PIN) )
			{
				flag = 0x01;			
			}
			j = 0;
			while( gpio_get_value(PIN) )
			{
				udelay(10);
				j++;
				if(j > 60)
				break;
			}
			data<<=1;
			data|=flag;
		}
		buf[i] = data;
	}
	buf[5] = buf[0] + buf[1] + buf[2] + buf[3];
	if(buf[4] == buf[5])
	{
		check_flag = 0xff;
		printk("humidity check pass\n");
		printk("humidity=[%d],temp=[%d]\n", buf[0], buf[2]);
	}
	else
	{
		check_flag = 0x0;
		printk("humidity check fail\n");           
	}                   
}

static ssize_t humidiy_read(struct file *file, char* buffer, size_t size, loff_t *off)
{
        int ret;
        local_irq_disable();
        humidity_read_data();
        local_irq_enable();
        if(check_flag == 0xff)
		{
			ret = copy_to_user(buffer,buf,sizeof(buf));
			if(ret < 0)
			{
				printk("copy to user err\n");
				return -EAGAIN;
            }
            else
            {
            	return 0;
			}
         }
         else
         {
         	return -EAGAIN;
		 }
}

static int humidiy_open(struct inode *inode, struct file *file)
{
    printk("open in kernel\n");
    return 0;
}

static int humidiy_release(struct inode *inode, struct file *file)
{
    printk("humidity release\n");
    return 0;
}

static struct file_operations humidity_dev_fops={
    owner		:	THIS_MODULE,
    open		:	humidiy_open,
	read		:	humidiy_read,
	release		:	humidiy_release,
};
static struct class *dht_class;

static int __init humidity_dev_init(void) 
{
	/*
 	 * Register device
 	 */
	int	ret;

	ret = register_chrdev(DEVICE_MAJOR, DEVICE_NAME, &humidity_dev_fops);
	if (ret < 0) {
		printk(KERN_INFO "%s: registering device %s with major %d failed with %d\n",
		       __func__, DEVICE_NAME, DEVICE_MAJOR, DEVICE_MAJOR );
		return(ret);
	}
	printk("DHT11 driver register success!\n");
	
	dht_class = class_create(THIS_MODULE, "dht11");
        if (IS_ERR(dht_class))
	{
		printk(KERN_WARNING "Can't make node %d\n", DEVICE_MAJOR);
                return PTR_ERR(dht_class);
	}

    device_create(dht_class, NULL, MKDEV(DEVICE_MAJOR, 0), NULL, DEVICE_NAME);
        
	printk("DHT11 driver make node success!\n");
	
	// Reserve gpios
	if( gpio_request( PIN, DEVICE_NAME ) < 0 )	// request pin 2
	{
		printk( KERN_INFO "%s: %s unable to get TRIG gpio\n", DEVICE_NAME, __func__ );
		ret = -EBUSY;
		return(ret);
	}
	
	// Set gpios directions
	if( gpio_direction_output( PIN, 1) < 0 )	// Set pin 2 as output with default value 0
	{
		printk( KERN_INFO "%s: %s unable to set TRIG gpio as output\n", DEVICE_NAME, __func__ );
		ret = -EBUSY;
		return(ret);
	}
	
    return 0;
}

static void __exit humidity_dev_exit(void)
{
    gpio_free(PIN);
    unregister_chrdev(DEVICE_MAJOR, DEVICE_NAME);
}

module_init(humidity_dev_init);
module_exit(humidity_dev_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("WWW");