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嵌入式Linux驱动开发笔记（未完待续。。。）
一、Git仓库用法
1、linu终端输入下面命令安装
git clone https://e.coding.net/weidongshan/linux_course/linux_basic_develop.git- 1
2、
进入到GIT仓库目录cd /D/abc/doc_and_source_for_mcu_mpu- 1
在doc_and_source_for_mcu_mpu目录下，执行以下命令获得资料的最新版本。
git pull origin- 1
二、字符设备驱动开发
1、hello驱动程序步骤
- 创建
file_operations结构体（字符设备驱动的核心） - 注册字符设备设备
- 写入口函数（相当于main）
- 写退出函数
三、字符设备驱动程序源码
#include#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static int major; static int hello_open (struct inode *node, struct file *filp) { printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__); return 0; } static ssize_t hello_read (struct file *filp, char __user *buf, size_t size, loff_t *offset) { printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__); return size; } static ssize_t hello_write(struct file *filp, const char __user *buf, size_t size, loff_t *offset) { printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__); return size; } static int hello_release (struct inode *node, struct file *filp) { printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__); return 0; } /* 1. create file_operations */ static const struct file_operations hello_drv = { .owner = THIS_MODULE, .read = hello_read, .write = hello_write, .open = hello_open, .release = hello_release, }; /* 2. register_chrdev */ /* 3. entry function */ static int hello_init(void) { major = register_chrdev(0, "100ask_hello", &hello_drv); return 0; } /* 4. exit function */ static void hello_exit(void) { unregister_chrdev(major, "100ask_hello"); } module_init(hello_init); module_exit(hello_exit); MODULE_LICENSE("GPL"); - 1
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用户与内核传数据和创建设备文件驱动程序#include "asm/cacheflush.h" #include#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static struct class *hello_class; //定义一个类型，用于创建设备 static int major; //主设备号 static unsigned char hello_buf[100]; //内核数据缓存 static int hello_open (struct inode *node, struct file *filp) { printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__); return 0; } static ssize_t hello_read (struct file *filp, char __user *buf, size_t size, loff_t *offset) { unsigned long len = size > 100 ? 100 : size; printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__); copy_to_user(buf, hello_buf, len); //将内核数据发送给用户 return len; } static ssize_t hello_write(struct file *filp, const char __user *buf, size_t size, loff_t *offset) { unsigned long len = size > 100 ? 100 : size; printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__); copy_from_user(hello_buf, buf, len); return len; } static int hello_release(struct inode *node, struct file *filp) { printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__); return 0; } /* 1. create file_operations */ static const struct file_operations hello_drv = { .owner = THIS_MODULE, .read = hello_read, .write = hello_write, .open = hello_open, .release = hello_release, }; /* 2. register_chrdev */ /* 3. entry function */ static int hello_init(void) { //申请设备号，只能进行注测主设备号0-255个设备，次设备号全部被占用 major = register_chrdev(0, "100ask_hello", &hello_drv); //0代表自动寻找设备号， hello_class = class_create(THIS_MODULE, "hello_class"); //创建一个类型 if (IS_ERR(hello_class)) { printk("failed to allocate class\n"); return PTR_ERR(hello_class); } //创建一个名字为hello的设备 device_create(hello_class, NULL, MKDEV(major, 0), NULL, "hello"); /* /dev/hello */ return 0; } /* 4. exit function */ static void hello_exit(void) { device_destroy(hello_class, MKDEV(major, 0)); class_destroy(hello_class); unregister_chrdev(major, "100ask_hello"); } module_init(hello_init); module_exit(hello_exit); MODULE_LICENSE("GPL"); - 1
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应用
#include#include #include #include #include #include /* 写: ./hello_test /dev/xxx 100ask * 读: ./hello_test /dev/xxx */ int main(int argc, char **argv) { int fd; int len; char buf[100]; if (argc < 2) { printf("Usage: \n"); printf("%s [string]\n" , argv[0]); return -1; } // open fd = open(argv[1], O_RDWR); if (fd < 0) { printf("can not open file %s\n", argv[1]); return -1; } if (argc == 3) { // write len = write(fd, argv[2], strlen(argv[2])+1); printf("write ret = %d\n", len); } else { // read len = read(fd, buf, 100); buf[99] = '\0'; printf("read str : %s\n", buf); } // close close(fd); return 0; }- 1
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四、 APP使用驱动的4种方式
1、驱动程序：提供能力，不提供策略
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非阻塞(查询)
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阻塞(休眠-唤醒)
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poll(定个闹钟)
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异步通知
妈妈怎么知道卧室里小孩醒了？ -
时不时进房间看一下： 查询方式
- 简单，但是累
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进去房间陪小孩一起睡觉，小孩醒了会吵醒她： 休眠-唤醒
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不累，但是妈妈干不了活了
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妈妈要干很多活，但是可以陪小孩睡一会，定个闹钟： poll 方式
- 要浪费点时间， 但是可以继续干活。
- 妈妈要么是被小孩吵醒，要么是被闹钟吵醒。
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妈妈在客厅干活，小孩醒了他会自己走出房门告诉妈妈： 异步通知
- 妈妈、小孩互不耽误
2、中断的引入
- 非阻塞：没有解除睡眠立即返回错误
- 阻塞如下图：
- poll机制如下图
- 异步通知
五、 字符设备的另一种注册方法cdev
驱动程序
#include "asm-generic/errno-base.h" #include "asm/cacheflush.h" #include "linux/cdev.h" #include "linux/fs.h" #include#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static struct class *hello_class; static struct cdev hello_cdev; static dev_t dev; static unsigned char hello_buf[100]; static int hello_open (struct inode *node, struct file *filp) { printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__); return 0; } static ssize_t hello_read (struct file *filp, char __user *buf, size_t size, loff_t *offset) { unsigned long len = size > 100 ? 100 : size; printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__); copy_to_user(buf, hello_buf, len); return len; } static ssize_t hello_write(struct file *filp, const char __user *buf, size_t size, loff_t *offset) { unsigned long len = size > 100 ? 100 : size; printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__); copy_from_user(hello_buf, buf, len); return len; } static int hello_release (struct inode *node, struct file *filp) { printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__); return 0; } /* 1. create file_operations */ static const struct file_operations hello_drv = { .owner = THIS_MODULE, .read = hello_read, .write = hello_write, .open = hello_open, .release = hello_release, }; /* 2. register_chrdev */ /* 3. entry function */ static int hello_init(void) { int ret; // register_chrdev //参数一：分配设备号成功后用来存放分配到的设备号，分配结束后要把主设备号提取出来（major = MAJOR(devno);)因为主设备号会变所以要将变得重新赋值 //参数二：起始的次设备号，一般为0 //参数三：count：申请的设备数量，从起始设备号累加。如果在创建一个设备，主设备号跟前一个一样，次设备号为1的设备，依然可以访问，就是同一个设备。 //参数四：/proc/devices文件中与该设备对应的名字，方便用户层查询主次设备号 ret = alloc_chrdev_region(&dev, 0, 2, "hello"); //自动注册设备 if (ret < 0) { printk(KERN_ERR "alloc_chrdev_region() failed for hello\n"); return -EINVAL; } cdev_init(&hello_cdev, &hello_drv); //将hello_drv与hello_cdev链接起来 ret = cdev_add(&hello_cdev, dev, 2);//将设备号添加到设备结构体 if (ret) { printk(KERN_ERR "cdev_add() failed for hello\n"); return -EINVAL; } hello_class = class_create(THIS_MODULE, "hello_class"); if (IS_ERR(hello_class)) { printk("failed to allocate class\n"); return PTR_ERR(hello_class); } //创建一名字为hello的设备 device_create(hello_class, NULL, dev, NULL, "hello"); /* /dev/hello */ return 0; } /* 4. exit function */ static void hello_exit(void) { device_destroy(hello_class, dev); class_destroy(hello_class); //unregister_chrdev(major, "100ask_hello"); cdev_del(&hello_cdev); unregister_chrdev_region(dev, 2); } module_init(hello_init); module_exit(hello_exit); MODULE_LICENSE("GPL"); - 1
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app
#include#include #include #include #include #include /* 写: ./hello_test /dev/xxx 100ask * 读: ./hello_test /dev/xxx */ int main(int argc, char **argv) { int fd; int len; char buf[100]; if (argc < 2) { printf("Usage: \n"); printf("%s [string]\n" , argv[0]); return -1; } // open fd = open(argv[1], O_RDWR); if (fd < 0) { printf("can not open file %s\n", argv[1]); return -1; } if (argc == 3) { // write len = write(fd, argv[2], strlen(argv[2])+1); printf("write ret = %d\n", len); } else { // read len = read(fd, buf, 100); buf[99] = '\0'; printf("read str : %s\n", buf); } // close close(fd); return 0; }- 1
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六、 通用框架1
1、GPIO子系统
在开发板上执行如下命令查看已经在使用的GPIO状态：# cat /sys/kernel/debug/gpio gpiochip0: GPIOs 0-15, parent: platform/soc:pin-controller@50002000, GPIOA: gpio-10 ( |heartbeat ) out lo gpio-14 ( |shutdown ) out hi gpiochip1: GPIOs 16-31, parent: platform/soc:pin-controller@50002000, GPIOB: gpio-26 ( |reset ) out hi ACTIVE LOW gpiochip2: GPIOs 32-47, parent: platform/soc:pin-controller@50002000, GPIOC: gpiochip3: GPIOs 48-63, parent: platform/soc:pin-controller@50002000, GPIOD:- 1
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怎么确定GPIO引脚的编号？方法如下：
① 先在开发板的/sys/class/gpio目录下，找到各个gpiochipXXX目录：（这个后面的数是起始地址，不跟上面那个查到的组数一样）
② 然后进入某个gpiochipXXX目录，查看文件label的内容，就可以知道起始号码XXX对于哪组GPIO
那么GPIO4_14的号码是96+14=110，可以如下操作读取按键值：[root@100ask:~]# echo 110 > /sys/class/gpio/export // gpio_request [root@100ask:~]# echo in > /sys/class/gpio/gpio110/direction // gpio_direction_input [root@100ask:~]# cat /sys/class/gpio/gpio110/value // gpio_get_value [root@100ask:~]# echo 110 > /sys/class/gpio/unexport // gpio_free- 1
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GPIO子系统函数有新、老两套：
descriptor-based legacy 获得GPIO gpiod_get gpio_request gpiod_get_index gpiod_get_array gpio_request_array devm_gpiod_get devm_gpiod_get_index devm_gpiod_get_array 设置方向 gpiod_direction_input gpio_direction_input gpiod_direction_output gpio_direction_output 读值、写值 gpiod_get_value gpio_get_value gpiod_set_value gpio_set_value 释放GPIO gpio_free gpio_free gpiod_put gpio_free_array gpiod_put_array devm_gpiod_put devm_gpiod_put_array 2、中断函数
2.1 使用中断的流程
在驱动程序里使用中断的流程如下：
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确定中断号
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注册中断处理函数，函数原型如下：
int request_irq(unsigned int irq, irq_handler_t handler, unsigned long flags, const char *name, void *dev);- 1
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在中断处理函数里
- 分辨中断
- 处理中断
- 清除中断
2.2 函数细节
request_irq函数的第1个参数是中断号，可以根据GPIO函数获得中断号：
int gpio_to_irq(unsigned int gpio); int gpiod_to_irq(const struct gpio_desc *desc);- 1
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request_irq函数的第2个参数是函数指针：
enum irqreturn { IRQ_NONE = (0 << 0), IRQ_HANDLED = (1 << 0), IRQ_WAKE_THREAD = (1 << 1), }; typedef enum irqreturn irqreturn_t; typedef irqreturn_t (*irq_handler_t)(int irq, void *dev);- 1
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request_irq函数的第3个参数有如下取值：
（上升沿触发、下降沿触发…）#define IRQF_TRIGGER_NONE 0x00000000 #define IRQF_TRIGGER_RISING 0x00000001 #define IRQF_TRIGGER_FALLING 0x00000002 #define IRQF_TRIGGER_HIGH 0x00000004 #define IRQF_TRIGGER_LOW 0x00000008 #define IRQF_SHARED 0x00000080- 1
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request_irq函数的第4个参数是中断的名字，可以在执行
cat /proc/interrupts的结果里查看。request_irq函数的第5个参数是给中断处理函数使用的。
2.3 代码driver
#include#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include struct gpio_desc{ //定义一个中断结构体 int gpio; int irq; char *name; int key; struct timer_list key_timer; } ; static struct gpio_desc gpios[2] = { //中断结构体赋初值 {131, 0, "gpio_100ask_1", 1,}, {132, 0, "gpio_100ask_2", 2,}, }; /* 主设备号 */ static int major = 0; static struct class *gpio_class; /* 环形缓冲区 */ #define BUF_LEN 128 static int g_keys[BUF_LEN]; static int r, w; struct fasync_struct *button_fasync; #define NEXT_POS(x) ((x+1) % BUF_LEN) static int is_key_buf_empty(void) { return (r == w); } static int is_key_buf_full(void) { return (r == NEXT_POS(w)); } static void put_key(int key) { if (!is_key_buf_full()) { g_keys[w] = key; w = NEXT_POS(w); } } static int get_key(void) { int key = 0; if (!is_key_buf_empty()) { key = g_keys[r]; r = NEXT_POS(r); } return key; } static DECLARE_WAIT_QUEUE_HEAD(gpio_wait); // static void key_timer_expire(struct timer_list *t) static void key_timer_expire(unsigned long data) { /* data ==> gpio */ // struct gpio_desc *gpio_desc = from_timer(gpio_desc, t, key_timer); struct gpio_desc *gpio_desc = (struct gpio_desc *)data; int val; int key; val = gpio_get_value(gpio_desc->gpio); //读取引脚 0或1 //printk("key_timer_expire key %d %d\n", gpio_desc->gpio, val); key = (gpio_desc->key) | (val<<8); //key值用来放在环形数组中，用key第八位看按键是否按下 put_key(key);//放入环形数组 wake_up_interruptible(&gpio_wait); kill_fasync(&button_fasync, SIGIO, POLL_IN); } /* 实现对应的open/read/write等函数，填入file_operations结构体 */ static ssize_t gpio_drv_read (struct file *file, char __user *buf, size_t size, loff_t *offset) { //printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); int err; int key; if (is_key_buf_empty() && (file->f_flags & O_NONBLOCK)) return -EAGAIN; wait_event_interruptible(gpio_wait,!is_key_buf_empty()); key = get_key(); err = copy_to_user(buf, &key, 4); return 4; } static ssize_t gpio_drv_write(struct file *file, const char __user *buf, size_t size, loff_t *offset) { unsigned char ker_buf[2]; int err; if (size != 2) return -EINVAL; err = copy_from_user(ker_buf, buf, size); if (ker_buf[0] >= sizeof(gpios)/sizeof(gpios[0])) return -EINVAL; gpio_set_value(gpios[ker_buf[0]].gpio, ker_buf[1]); return 2; } static unsigned int gpio_drv_poll(struct file *fp, poll_table * wait) { //printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); poll_wait(fp, &gpio_wait, wait); return is_key_buf_empty() ? 0 : POLLIN | POLLRDNORM; } static int gpio_drv_fasync(int fd, struct file *file, int on) { if (fasync_helper(fd, file, on, &button_fasync) >= 0) return 0; else return -EIO; } /* 定义自己的file_operations结构体 */ static struct file_operations gpio_key_drv = { .owner = THIS_MODULE, .read = gpio_drv_read, .write = gpio_drv_write, .poll = gpio_drv_poll, .fasync = gpio_drv_fasync, }; static irqreturn_t gpio_key_isr(int irq, void *dev_id) { struct gpio_desc *gpio_desc = dev_id; printk("gpio_key_isr key %d irq happened\n", gpio_desc->gpio); //jiffies是全局变量 mod_timer(&gpio_desc->key_timer, jiffies + HZ/5); //消抖，每次抖动时长小于（HZ/5）*Tms，都会推迟进入中断服务程序 return IRQ_HANDLED; } /* 在入口函数 */ static int __init gpio_drv_init(void) { int err; int i; int count = sizeof(gpios)/sizeof(gpios[0]); printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); for (i = 0; i < count; i++) { gpios[i].irq = gpio_to_irq(gpios[i].gpio); //调用函数获得中断号 //定时器初始化函数 参数一：定时器时间 参数二：中断服务程序 参数三：传入中断服务程序的参数 setup_timer(&gpios[i].key_timer, key_timer_expire, (unsigned long)&gpios[i]); //timer_setup(&gpios[i].key_timer, key_timer_expire, 0); gpios[i].key_timer.expires = ~0; add_timer(&gpios[i].key_timer); err = request_irq(gpios[i].irq, gpio_key_isr, IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING, "100ask_gpio_key", &gpios[i]); //注册中断 } /* 注册file_operations */ major = register_chrdev(0, "100ask_gpio_key", &gpio_key_drv); /* /dev/gpio_desc */ gpio_class = class_create(THIS_MODULE, "100ask_gpio_key_class"); if (IS_ERR(gpio_class)) { printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); unregister_chrdev(major, "100ask_gpio_key"); return PTR_ERR(gpio_class); } device_create(gpio_class, NULL, MKDEV(major, 0), NULL, "100ask_gpio"); /* /dev/100ask_gpio */ return err; } /* 有入口函数就应该有出口函数：卸载驱动程序时，就会去调用这个出口函数 */ static void __exit gpio_drv_exit(void) { int i; int count = sizeof(gpios)/sizeof(gpios[0]); printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); device_destroy(gpio_class, MKDEV(major, 0)); class_destroy(gpio_class); unregister_chrdev(major, "100ask_gpio_key"); for (i = 0; i < count; i++) { free_irq(gpios[i].irq, &gpios[i]); del_timer(&gpios[i].key_timer); } } /* 7. 其他完善：提供设备信息，自动创建设备节点 */ module_init(gpio_drv_init); module_exit(gpio_drv_exit); MODULE_LICENSE("GPL"); - 1
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app
#include#include #include #include #include #include #include #include static int fd; /* * ./button_test /dev/100ask_button0 * */ int main(int argc, char **argv) { int val; struct pollfd fds[1]; int timeout_ms = 5000; int ret; int flags; int i; /* 1. 判断参数 */ if (argc != 2) { printf("Usage: %s \n" , argv[0]); return -1; } /* 2. 打开文件 */ fd = open(argv[1], O_RDWR | O_NONBLOCK); if (fd == -1) { printf("can not open file %s\n", argv[1]); return -1; } for (i = 0; i < 10; i++) { if (read(fd, &val, 4) == 4) printf("get button: 0x%x\n", val); else printf("get button: -1\n"); } flags = fcntl(fd, F_GETFL); fcntl(fd, F_SETFL, flags & ~O_NONBLOCK); while(1) { if (read(fd, &val, 4) == 4) printf("get button: 0x%x\n", val); else printf("while get button: -1\n"); } close(fd); return 0; }- 1
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非阻塞及环形读写
阻塞访问
POLL机制
异步通知
LED驱动编写（imx6ull）
driver#include "asm-generic/errno-base.h" #include "asm-generic/gpio.h" #include "asm/uaccess.h" #include#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include struct gpio_desc{ int gpio; int irq; char *name; int key; struct timer_list key_timer; } ; static struct gpio_desc gpios[2] = { {131, 0, "led0", }, //{132, 0, "led1", }, }; /* 主设备号 */ static int major = 0; static struct class *gpio_class; /* 实现对应的open/read/write等函数，填入file_operations结构体 */ static ssize_t gpio_drv_read (struct file *file, char __user *buf, size_t size, loff_t *offset) { char tmp_buf[2]; int err; int count = sizeof(gpios)/sizeof(gpios[0]); //表示有多少可操作引脚 if (size != 2) return -EINVAL; err = copy_from_user(tmp_buf, buf, 1); if (tmp_buf[0] >= count) //大于可操作数量报错 return -EINVAL; tmp_buf[1] = gpio_get_value(gpios[tmp_buf[0]].gpio); err = copy_to_user(buf, tmp_buf, 2); return 2; } static ssize_t gpio_drv_write(struct file *file, const char __user *buf, size_t size, loff_t *offset) { unsigned char ker_buf[2]; //内核数组 int err; if (size != 2) //传入的参数不是2直接退出 return -EINVAL; err = copy_from_user(ker_buf, buf, size); //将用户数据拷贝到内核 if (ker_buf[0] >= sizeof(gpios)/sizeof(gpios[0])) //大于课操作引脚报错 return -EINVAL; gpio_set_value(gpios[ker_buf[0]].gpio, ker_buf[1]); return 2; } /* 定义自己的file_operations结构体 */ static struct file_operations gpio_key_drv = { .owner = THIS_MODULE, .read = gpio_drv_read, .write = gpio_drv_write, }; /* 在入口函数 */ static int __init gpio_drv_init(void) { int err; int i; int count = sizeof(gpios)/sizeof(gpios[0]); printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); for (i = 0; i < count; i++) { /* set pin as output */ err = gpio_request(gpios[i].gpio, gpios[i].name);//其实就是让内核检查一下该GPIO引脚是否被其它设备占用，如果没有占用则返回0并用label做一下标记，表示被本设备占用，否则返回负数 if (err < 0) { printk("can not request gpio %s %d\n", gpios[i].name, gpios[i].gpio); return -ENODEV; } (gpios[i].gpio, 1); //设置gpio输出为1 } /* 注册file_operations */ major = register_chrdev(0, "100ask_led", &gpio_key_drv); /* /dev/gpio_desc */ gpio_class = class_create(THIS_MODULE, "100ask_led_class"); if (IS_ERR(gpio_class)) { printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); unregister_chrdev(major, "100ask_led_class"); return PTR_ERR(gpio_class); } device_create(gpio_class, NULL, MKDEV(major, 0), NULL, "100ask_led"); /* /dev/100ask_gpio */ return err; } /* 有入口函数就应该有出口函数：卸载驱动程序时，就会去调用这个出口函数 */ static void __exit gpio_drv_exit(void) { int i; int count = sizeof(gpios)/sizeof(gpios[0]); printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); device_destroy(gpio_class, MKDEV(major, 0)); class_destroy(gpio_class); unregister_chrdev(major, "100ask_led"); for (i = 0; i < count; i++) { gpio_free(gpios[i].gpio); } } /* 7. 其他完善：提供设备信息，自动创建设备节点 */ module_init(gpio_drv_init); module_exit(gpio_drv_exit); MODULE_LICENSE("GPL"); - 1
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#include#include #include #include #include #include #include #include #include static int fd; //int led_on(int which); //int led_off(int which); //int led_status(int which); /* * ./led_test <0|1|2|..> on * ./led_test <0|1|2|..> off * ./led_test <0|1|2|..> */ int main(int argc, char **argv) { int ret; char buf[2]; int i; /* 1. 判断参数 */ if (argc < 2) { printf("Usage: %s <0|1|2|...> [on | off]\n", argv[0]); return -1; } /* 2. 打开文件 */ fd = open("/dev/100ask_led", O_RDWR); if (fd == -1) { printf("can not open file /dev/100ask_led\n"); return -1; } if (argc == 3) { /* write */ buf[0] = strtol(argv[1], NULL, 0); //将字符串内容转化成整数 if (strcmp(argv[2], "on") == 0) //strcmp字符串比较，如果相等返回0 buf[1] = 0; else buf[1] = 1; ret = write(fd, buf, 2); } else { buf[0] = strtol(argv[1], NULL, 0); ret = read(fd, buf, 2); if (ret == 2) { printf("led %d status is %s\n", buf[0], buf[1] == 0 ? "on" : "off"); } } close(fd); return 0; } - 1
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SR501红外模块驱动编写（imx6ull）
驱动#include#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include struct gpio_desc{ //定义一个gpio结构体 int gpio; int irq; char *name; int key; struct timer_list key_timer; } ; static struct gpio_desc gpios[2] = { //赋初值 {115, 0, "sr501", }, //io口的编号，0号中断，名称 }; /* 主设备号 */ static int major = 0; static struct class *gpio_class; //定义一个设备类结构体 /* 环形缓冲区 */ #define BUF_LEN 128 // static int g_keys[BUF_LEN]; //内核数据接收缓冲区 static int r, w; struct fasync_struct *button_fasync; //异步通信用的信号结构体，他可以提供一个pid用于信号通信 #define NEXT_POS(x) ((x+1) % BUF_LEN) //环形接收对数组的下标操作 static int is_key_buf_empty(void) //接收数组为空 { return (r == w); } static int is_key_buf_full(void) //如果接收数组已满将 { return (r == NEXT_POS(w)); //读下标等于写下标(x)+1就代表满了 } static void put_key(int key) //按键按下 { if (!is_key_buf_full()) //没满 { g_keys[w] = key; //存按键值 w = NEXT_POS(w); //写下标加一 } } static int get_key(void) //获得按键值 { int key = 0; if (!is_key_buf_empty()) //不为空 { key = g_keys[r]; //读取按键键值 r = NEXT_POS(r); //读下标加一 } return key; //返回按键键值 } static DECLARE_WAIT_QUEUE_HEAD(gpio_wait); //初始化gpio休眠队列 /* 实现对应的open/read/write等函数，填入file_operations结构体 */ static ssize_t gpio_drv_read (struct file *file, char __user *buf, size_t size, loff_t *offset) //按键读取驱动程序，因为是电子按键所以不用消抖 { //printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); int err; int key; if (is_key_buf_empty() && (file->f_flags & O_NONBLOCK)) //如果非阻塞还为空直接返回 return -EAGAIN; wait_event_interruptible(gpio_wait, !is_key_buf_empty()); //等待如果不为空进行下一步 key = get_key(); //获取键值 err = copy_to_user(buf, &key, 4); //将键值发送给用户 return 4; } static unsigned int gpio_drv_poll(struct file *fp, poll_table * wait) //poll机制，这次没用着 { //printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); poll_wait(fp, &gpio_wait, wait); //加入等待队列 return is_key_buf_empty() ? 0 : POLLIN | POLLRDNORM; } static int gpio_drv_fasync(int fd, struct file *file, int on) //构造button_fasync结构体，方便后面程序寻找pid { if (fasync_helper(fd, file, on, &button_fasync) >= 0) return 0; else return -EIO; } /* 定义自己的file_operations结构体 */ static struct file_operations gpio_key_drv = { .owner = THIS_MODULE, .read = gpio_drv_read, .poll = gpio_drv_poll, .fasync = gpio_drv_fasync, }; static irqreturn_t gpio_key_isr(int irq, void *dev_id) //按键中断 { struct gpio_desc *gpio_desc = dev_id; int val; int key; printk("gpio_key_isr key %d irq happened\n", gpio_desc->gpio); val = gpio_get_value(gpio_desc->gpio); //printk("key_timer_expire key %d %d\n", gpio_desc->gpio, val); key = (gpio_desc->key) | (val<<8); put_key(key); wake_up_interruptible(&gpio_wait); kill_fasync(&button_fasync, SIGIO, POLL_IN); return IRQ_HANDLED; } /* 在入口函数 */ static int __init gpio_drv_init(void) { int err; int i; int count = sizeof(gpios)/sizeof(gpios[0]); printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); for (i = 0; i < count; i++) { gpios[i].irq = gpio_to_irq(gpios[i].gpio); err = request_irq(gpios[i].irq, gpio_key_isr, IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING, gpios[i].name, &gpios[i]); //使能按键中断，中断号为gpios[i].irq，中断服务函数gpio_key_isr，触发方式为上升沿下降沿触发IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING } /* 注册file_operations */ major = register_chrdev(0, "100ask_gpio_key", &gpio_key_drv); /* /dev/gpio_desc */ gpio_class = class_create(THIS_MODULE, "100ask_gpio_key_class"); if (IS_ERR(gpio_class)) { printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); unregister_chrdev(major, "100ask_gpio_key"); return PTR_ERR(gpio_class); } device_create(gpio_class, NULL, MKDEV(major, 0), NULL, "sr501"); /* /dev/sr501 */ return err; } /* 有入口函数就应该有出口函数：卸载驱动程序时，就会去调用这个出口函数 */ static void __exit gpio_drv_exit(void) { int i; int count = sizeof(gpios)/sizeof(gpios[0]); printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); device_destroy(gpio_class, MKDEV(major, 0)); class_destroy(gpio_class); unregister_chrdev(major, "100ask_gpio_key"); for (i = 0; i < count; i++) { free_irq(gpios[i].irq, &gpios[i]); } } /* 7. 其他完善：提供设备信息，自动创建设备节点 */ module_init(gpio_drv_init); module_exit(gpio_drv_exit); MODULE_LICENSE("GPL"); - 1
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app
#include#include #include #include #include #include #include #include static int fd; /* * ./button_test /dev/sr501 * */ int main(int argc, char **argv) { int val; struct pollfd fds[1]; int timeout_ms = 5000; int ret; int flags; int i; /* 1. 判断参数 */ if (argc != 2) { printf("Usage: %s \n" , argv[0]); return -1; } /* 2. 打开文件 */ fd = open(argv[1], O_RDWR); if (fd == -1) { printf("can not open file %s\n", argv[1]); return -1; } while (1) { if (read(fd, &val, 4) == 4) printf("get button: 0x%x\n", val); else printf("get button: -1\n"); } close(fd); return 0; }- 1
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SR04超声波测距模块驱动
驱动
#include "asm-generic/gpio.h" #include "asm/delay.h" #include#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define CMD_TRIG 100 //ioctrl任务选择常量 struct gpio_desc{ int gpio; int irq; char *name; int key; struct timer_list key_timer; } ; static struct gpio_desc gpios[2] = { //定义两个io口 {115, 0, "trig", }, {116, 0, "echo", }, }; /* 主设备号 */ static int major = 0; static struct class *gpio_class; /* 环形缓冲区 */ #define BUF_LEN 128 static int g_keys[BUF_LEN]; static int r, w; struct fasync_struct *button_fasync; #define NEXT_POS(x) ((x+1) % BUF_LEN) static int is_key_buf_empty(void) { return (r == w); } static int is_key_buf_full(void) { return (r == NEXT_POS(w)); } static void put_key(int key) { if (!is_key_buf_full()) { g_keys[w] = key; w = NEXT_POS(w); } } static int get_key(void) { int key = 0; if (!is_key_buf_empty()) { key = g_keys[r]; r = NEXT_POS(r); } return key; } static DECLARE_WAIT_QUEUE_HEAD(gpio_wait); /* 实现对应的open/read/write等函数，填入file_operations结构体 */ static ssize_t sr04_read (struct file *file, char __user *buf, size_t size, loff_t *offset) { //printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); int err; int key; if (is_key_buf_empty() && (file->f_flags & O_NONBLOCK)) return -EAGAIN; // printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); 加上这条语句就读不出来数据了，可能是函数内部关了中断 wait_event_interruptible(gpio_wait, !is_key_buf_empty()); key = get_key(); err = copy_to_user(buf, &key, 4); return 4; } static unsigned int sr04_poll(struct file *fp, poll_table * wait) { //printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); poll_wait(fp, &gpio_wait, wait); return is_key_buf_empty() ? 0 : POLLIN | POLLRDNORM; } static int sr04_fasync(int fd, struct file *file, int on) { if (fasync_helper(fd, file, on, &button_fasync) >= 0) return 0; else return -EIO; } // ioctl(fd, CMD, ARG) static long sr04_ioctl(struct file *filp, unsigned int command, unsigned long arg) { // send trig switch (command) { case CMD_TRIG: { //printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); gpio_set_value(gpios[0].gpio, 1); //根据超声波传感器手册启动前要发送一个20us高电平 udelay(20); gpio_set_value(gpios[0].gpio, 0); } } return 0; } /* 定义自己的file_operations结构体 */ static struct file_operations sr04_drv = { .owner = THIS_MODULE, .read = sr04_read, .poll = sr04_poll, .fasync = sr04_fasync, .unlocked_ioctl = sr04_ioctl, }; static irqreturn_t sr04_isr(int irq, void *dev_id) { struct gpio_desc *gpio_desc = dev_id; int val; static u64 rising_time = 0; u64 time; val = gpio_get_value(gpio_desc->gpio); //printk("sr04_isr echo pin %d is %d\n", gpio_desc->gpio, val);如果加上打印会超时 if (val) { /* 上升沿记录起始时间 */ rising_time = ktime_get_ns(); } else { if (rising_time == 0) { //printk("missing rising interrupt\n"); return IRQ_HANDLED; } /* 下降沿记录结束时间, 并计算时间差, 计算距离 */ time = ktime_get_ns() - rising_time; rising_time = 0; put_key(time); wake_up_interruptible(&gpio_wait); kill_fasync(&button_fasync, SIGIO, POLL_IN); } return IRQ_HANDLED; } /* 在入口函数 */ static int __init sr04_init(void) { int err; printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); // trig pin err = gpio_request(gpios[0].gpio, gpios[0].name); gpio_direction_output(gpios[0].gpio, 0); // echo pin { gpios[1].irq = gpio_to_irq(gpios[1].gpio); //获取中断号 err = request_irq(gpios[1].irq, sr04_isr, IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING, gpios[1].name, &gpios[1]); //初始化按键中断 } /* 注册file_operations */ major = register_chrdev(0, "100ask_sr04", &sr04_drv); /* /dev/gpio_desc */ gpio_class = class_create(THIS_MODULE, "100ask_sr04_class"); if (IS_ERR(gpio_class)) { printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); unregister_chrdev(major, "100ask_sr04"); return PTR_ERR(gpio_class); } device_create(gpio_class, NULL, MKDEV(major, 0), NULL, "sr04"); /* /dev/sr04 */ return err; } /* 有入口函数就应该有出口函数：卸载驱动程序时，就会去调用这个出口函数 */ static void __exit sr04_exit(void) { printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); device_destroy(gpio_class, MKDEV(major, 0)); class_destroy(gpio_class); unregister_chrdev(major, "100ask_sr04"); // trig pin gpio_free(gpios[0].gpio); // echo pin { free_irq(gpios[1].irq, &gpios[1]); } } /* 7. 其他完善：提供设备信息，自动创建设备节点 */ module_init(sr04_init); module_exit(sr04_exit); MODULE_LICENSE("GPL"); - 1
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#include#include #include #include #include #include #include #include #include #define CMD_TRIG 100 static int fd; /* * ./button_test /dev/sr04 * */ int main(int argc, char **argv) { int val; struct pollfd fds[1]; int timeout_ms = 5000; int ret; int flags; int i; /* 1. 判断参数 */ if (argc != 2) { printf("Usage: %s \n" , argv[0]); return -1; } /* 2. 打开文件 */ fd = open(argv[1], O_RDWR); if (fd == -1) { printf("can not open file %s\n", argv[1]); return -1; } while (1) { ioctl(fd, CMD_TRIG); printf("I am goning to read distance: \n"); if (read(fd, &val, 4) == 4) printf("get distance: %d cm\n", val*17/1000000); else printf("get distance err\n"); sleep(1); //根据硬件时序图不能太快发送高电平 } close(fd); return 0; }- 1
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超声波测距程序改进（在app加入poll机制，或在驱动iocontrl里面加一个定时器）
#include "asm-generic/errno.h" #include "asm-generic/gpio.h" #include "asm/delay.h" #include "linux/jiffies.h" #include#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define CMD_TRIG 100 struct gpio_desc{ int gpio; int irq; char *name; int key; struct timer_list key_timer; } ; static struct gpio_desc gpios[2] = { {115, 0, "trig", }, {116, 0, "echo", }, }; /* 主设备号 */ static int major = 0; static struct class *gpio_class; /* 环形缓冲区 */ #define BUF_LEN 128 static int g_keys[BUF_LEN]; static int r, w; struct fasync_struct *button_fasync; #define NEXT_POS(x) ((x+1) % BUF_LEN) static int is_key_buf_empty(void) { return (r == w); } static int is_key_buf_full(void) { return (r == NEXT_POS(w)); } static void put_key(int key) { if (!is_key_buf_full()) { g_keys[w] = key; w = NEXT_POS(w); } } static int get_key(void) { int key = 0; if (!is_key_buf_empty()) { key = g_keys[r]; r = NEXT_POS(r); } return key; } static DECLARE_WAIT_QUEUE_HEAD(gpio_wait); /* 实现对应的open/read/write等函数，填入file_operations结构体 */ static ssize_t sr04_read (struct file *file, char __user *buf, size_t size, loff_t *offset) { //printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); int err; int key; if (is_key_buf_empty() && (file->f_flags & O_NONBLOCK)) return -EAGAIN; // printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); wait_event_interruptible(gpio_wait, !is_key_buf_empty()); key = get_key(); if (key == -1) return -ENODATA; err = copy_to_user(buf, &key, 4); return 4; } static unsigned int sr04_poll(struct file *fp, poll_table * wait) { //printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); poll_wait(fp, &gpio_wait, wait); return is_key_buf_empty() ? 0 : POLLIN | POLLRDNORM; } static int sr04_fasync(int fd, struct file *file, int on) { if (fasync_helper(fd, file, on, &button_fasync) >= 0) return 0; else return -EIO; } // ioctl(fd, CMD, ARG) static long sr04_ioctl(struct file *filp, unsigned int command, unsigned long arg) { // send trig switch (command) { case CMD_TRIG: { //printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); gpio_set_value(gpios[0].gpio, 1); udelay(20); gpio_set_value(gpios[0].gpio, 0); // start timer mod_timer(&gpios[1].key_timer, jiffies + msecs_to_jiffies(50)); //50ms后进入定时器服务程序 } } return 0; } /* 定义自己的file_operations结构体 */ static struct file_operations sr04_drv = { .owner = THIS_MODULE, .read = sr04_read, .poll = sr04_poll, .fasync = sr04_fasync, .unlocked_ioctl = sr04_ioctl, }; static irqreturn_t sr04_isr(int irq, void *dev_id) { struct gpio_desc *gpio_desc = dev_id; int val; static u64 rising_time = 0; u64 time; val = gpio_get_value(gpio_desc->gpio); //printk("sr04_isr echo pin %d is %d\n", gpio_desc->gpio, val); if (val) { /* 上升沿记录起始时间 */ rising_time = ktime_get_ns(); } else { if (rising_time == 0) { //printk("missing rising interrupt\n"); return IRQ_HANDLED; } /* 下降沿记录结束时间, 并计算时间差, 计算距离 */ // stop timer del_timer(&gpios[1].key_timer); time = ktime_get_ns() - rising_time; rising_time = 0; put_key(time); wake_up_interruptible(&gpio_wait); kill_fasync(&button_fasync, SIGIO, POLL_IN); } return IRQ_HANDLED; } static void sr04_timer_func(unsigned long data) //如果超时还没有接收到数据进入此函数 { put_key(-1); //在数组里写入-1 wake_up_interruptible(&gpio_wait); //唤醒睡眠，将-1发出去 kill_fasync(&button_fasync, SIGIO, POLL_IN); } /* 在入口函数 */ static int __init sr04_init(void) { int err; printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); // trig pin err = gpio_request(gpios[0].gpio, gpios[0].name); gpio_direction_output(gpios[0].gpio, 0); // echo pin { gpios[1].irq = gpio_to_irq(gpios[1].gpio); err = request_irq(gpios[1].irq, sr04_isr, IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING, gpios[1].name, &gpios[1]); setup_timer(&gpios[1].key_timer, sr04_timer_func, (unsigned long)&gpios[1]); } /* 注册file_operations */ major = register_chrdev(0, "100ask_sr04", &sr04_drv); /* /dev/gpio_desc */ gpio_class = class_create(THIS_MODULE, "100ask_sr04_class"); if (IS_ERR(gpio_class)) { printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); unregister_chrdev(major, "100ask_sr04"); return PTR_ERR(gpio_class); } device_create(gpio_class, NULL, MKDEV(major, 0), NULL, "sr04"); /* /dev/sr04 */ return err; } /* 有入口函数就应该有出口函数：卸载驱动程序时，就会去调用这个出口函数 */ static void __exit sr04_exit(void) { printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); device_destroy(gpio_class, MKDEV(major, 0)); class_destroy(gpio_class); unregister_chrdev(major, "100ask_sr04"); // trig pin gpio_free(gpios[0].gpio); // echo pin { free_irq(gpios[1].irq, &gpios[1]); del_timer(&gpios[1].key_timer); } } /* 7. 其他完善：提供设备信息，自动创建设备节点 */ module_init(sr04_init); module_exit(sr04_exit); MODULE_LICENSE("GPL"); - 1
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#include#include #include #include #include #include #include #include #include #define CMD_TRIG 100 static int fd; /* * ./button_test /dev/sr04 * */ int main(int argc, char **argv) { int val; struct pollfd fds[1]; int timeout_ms = 5000; int ret; int flags; int i; /* 1. 判断参数 */ if (argc != 2) { printf("Usage: %s \n" , argv[0]); return -1; } /* 2. 打开文件 */ fd = open(argv[1], O_RDWR); if (fd == -1) { printf("can not open file %s\n", argv[1]); return -1; } while (1) { ioctl(fd, CMD_TRIG); printf("I am goning to read distance: \n"); fds[0].fd = fd; fds[0].events = POLLIN; if (1 == poll(fds, 1, 5000)) //poll函数有数据返回的是个正数，数值为设备个数，超过5s会跳出阻塞返回值为0 { if (read(fd, &val, 4) == 4) printf("get distance: %d cm\n", val*17/1000000); else printf("get distance err\n"); } else { printf("get distance poll timeout/err\n"); } sleep(1); } close(fd); return 0; }- 1
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内核不同调用的函数不一样（内核哪里在入门视频第五章有讲）
步进电机控制原理与接线
编程思路
编程#include "asm-generic/gpio.h" #include "asm/gpio.h" #include#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include struct gpio_desc{ int gpio; int irq; char *name; int key; struct timer_list key_timer; } ; static struct gpio_desc gpios[] = { {115, 0, "motor_gpio0", }, {116, 0, "motor_gpio1", }, {117, 0, "motor_gpio2", }, {118, 0, "motor_gpio3", }, }; /* 主设备号 */ static int major = 0; static struct class *gpio_class; /* 马达引脚设置数字 */ static int g_motor_pin_ctrl[8]= {0x2,0x3,0x1,0x9,0x8,0xc,0x4,0x6}; static int g_motor_index = 0; void set_pins_for_motor(int index) { int i; for (i = 0; i < 4; i++) { gpio_set_value(gpios[i].gpio, g_motor_pin_ctrl[index] & (1<<i) ? 1 : 0); } } void disable_motor(void) { int i; for (i = 0; i < 4; i++) { gpio_set_value(gpios[i].gpio, 0); } } /* int buf[2]; * buf[0] = 步进的次数, > 0 : 逆时针步进; < 0 : 顺时针步进 * buf[1] = mdelay的时间 */ static ssize_t motor_write(struct file *file, const char __user *buf, size_t size, loff_t *offset) { int ker_buf[2]; int err; int step; if (size != 8) return -EINVAL; err = copy_from_user(ker_buf, buf, size); if (ker_buf[0] > 0) { /* 逆时针旋转 */ for (step = 0; step < ker_buf[0]; step++) { set_pins_for_motor(g_motor_index); mdelay(ker_buf[1]); g_motor_index--; if (g_motor_index == -1) g_motor_index = 7; } } else { /* 顺时针旋转 */ ker_buf[0] = 0 - ker_buf[0]; for (step = 0; step < ker_buf[0]; step++) { set_pins_for_motor(g_motor_index); mdelay(ker_buf[1]); g_motor_index++; if (g_motor_index == 8) g_motor_index = 0; } } /* 改进：旋转到位后让马达不再消耗电源 */ disable_motor(); return 8; } /* 定义自己的file_operations结构体 */ static struct file_operations gpio_key_drv = { .owner = THIS_MODULE, .write = motor_write, }; /* 在入口函数 */ static int __init motor_init(void) { int err; int i; int count = sizeof(gpios)/sizeof(gpios[0]); printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); for (i = 0; i < count; i++) { err = gpio_request(gpios[i].gpio, gpios[i].name); gpio_direction_output(gpios[i].gpio, 0); } /* 注册file_operations */ major = register_chrdev(0, "100ask_gpio_key", &gpio_key_drv); /* /dev/gpio_desc */ gpio_class = class_create(THIS_MODULE, "100ask_gpio_key_class"); if (IS_ERR(gpio_class)) { printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); unregister_chrdev(major, "100ask_gpio_key"); return PTR_ERR(gpio_class); } device_create(gpio_class, NULL, MKDEV(major, 0), NULL, "motor"); /* /dev/motor */ return err; } /* 有入口函数就应该有出口函数：卸载驱动程序时，就会去调用这个出口函数 */ static void __exit motor_exit(void) { int i; int count = sizeof(gpios)/sizeof(gpios[0]); printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); device_destroy(gpio_class, MKDEV(major, 0)); class_destroy(gpio_class); unregister_chrdev(major, "100ask_gpio_key"); for (i = 0; i < count; i++) { gpio_free(gpios[i].gpio); } } /* 7. 其他完善：提供设备信息，自动创建设备节点 */ module_init(motor_init); module_exit(motor_exit); MODULE_LICENSE("GPL"); - 1
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#include#include #include #include #include #include #include #include #include static int fd; /* * ./button_test /dev/motor -100 1 * */ int main(int argc, char **argv) { int buf[2]; int ret; /* 1. 判断参数 */ if (argc != 4) { printf("Usage: %s \n" - 1
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DHT11驱动程序编写
驱动#include "asm-generic/errno-base.h" #include "asm-generic/gpio.h" #include "linux/jiffies.h" #include#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include struct gpio_desc{ int gpio; int irq; char *name; int key; struct timer_list key_timer; } ; static struct gpio_desc gpios[] = { {115, 0, "dht11", }, }; /* 主设备号 */ static int major = 0; static struct class *gpio_class; static u64 g_dht11_irq_time[84]; static int g_dht11_irq_cnt = 0; /* 环形缓冲区 */ #define BUF_LEN 128 static char g_keys[BUF_LEN]; static int r, w; struct fasync_struct *button_fasync; static irqreturn_t dht11_isr(int irq, void *dev_id); static void parse_dht11_datas(void); #define NEXT_POS(x) ((x+1) % BUF_LEN) static int is_key_buf_empty(void) { return (r == w); } static int is_key_buf_full(void) { return (r == NEXT_POS(w)); } static void put_key(char key) { if (!is_key_buf_full()) { g_keys[w] = key; w = NEXT_POS(w); } } static char get_key(void) { char key = 0; if (!is_key_buf_empty()) { key = g_keys[r]; r = NEXT_POS(r); } return key; } static DECLARE_WAIT_QUEUE_HEAD(gpio_wait); // static void key_timer_expire(struct timer_list *t) static void key_timer_expire(unsigned long data) { // 解析数据, 放入环形buffer, 唤醒APP parse_dht11_datas(); } /* 实现对应的open/read/write等函数，填入file_operations结构体 */ static ssize_t dht11_read (struct file *file, char __user *buf, size_t size, loff_t *offset) { int err; char kern_buf[2]; if (size != 2) return -EINVAL; g_dht11_irq_cnt = 0; /* 1. 发送18ms的低脉冲 */ err = gpio_request(gpios[0].gpio, gpios[0].name); gpio_direction_output(gpios[0].gpio, 0); gpio_free(gpios[0].gpio); mdelay(18); gpio_direction_input(gpios[0].gpio); /* 引脚变为输入方向, 由上拉电阻拉为1 */ /* 2. 注册中断 */ err = request_irq(gpios[0].irq, dht11_isr, IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING, gpios[0].name, &gpios[0]); mod_timer(&gpios[0].key_timer, jiffies + 10); //超时后进入定时器中断服务程序，如果没超时（也就是接收到了84个脉冲）会在外部中断里把这个定时器删除 /* 3. 休眠等待数据 */ wait_event_interruptible(gpio_wait, !is_key_buf_empty()); free_irq(gpios[0].irq, &gpios[0]); //printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__); /* 设置DHT11 GPIO引脚的初始状态: output 1 */ err = gpio_request(gpios[0].gpio, gpios[0].name); if (err) { printk("%s %s %d, gpio_request err\n", __FILE__, __FUNCTION__, __LINE__); } gpio_direction_output(gpios[0].gpio, 1); gpio_free(gpios[0].gpio); /* 4. copy_to_user */ kern_buf[0] = get_key(); //只得到湿度跟温度的整数部分一共两个字节 kern_buf[1] = get_key(); printk("get val : 0x%x, 0x%x\n", kern_buf[0], kern_buf[1]); if ((kern_buf[0] == (char)-1) && (kern_buf[1] == (char)-1)) //必须强转为char因为arm-gcc编译器把char转成unsigned char { printk("get err val\n"); //在终端输入dmesg可以查看 return -EIO; } err = copy_to_user(buf, kern_buf, 2); return 2; } static int dht11_release (struct inode *inode, struct file *filp) { return 0; } /* 定义自己的file_operations结构体 */ static struct file_operations dht11_drv = { .owner = THIS_MODULE, .read = dht11_read, .release = dht11_release, }; static void parse_dht11_datas(void) { int i; u64 high_time; unsigned char data = 0; int bits = 0; unsigned char datas[5]; int byte = 0; unsigned char crc; /* 数据个数: 可能是81、82、83、84 */ if (g_dht11_irq_cnt < 81) { /* 出错 */ put_key(-1); put_key(-1); // 唤醒APP wake_up_interruptible(&gpio_wait); g_dht11_irq_cnt = 0; return; } // 解析数据 for (i = g_dht11_irq_cnt - 80; i < g_dht11_irq_cnt; i+=2) { high_time = g_dht11_irq_time[i] - g_dht11_irq_time[i-1]; data <<= 1; if (high_time > 50000) /* data 1 */ { data |= 1; } bits++; if (bits == 8) { datas[byte] = data; data = 0; bits = 0; byte++; } } // 放入环形buffer crc = datas[0] + datas[1] + datas[2] + datas[3]; if (crc == datas[4]) { put_key(datas[0]); put_key(datas[2]); } else { put_key(-1); put_key(-1); } g_dht11_irq_cnt = 0; // 唤醒APP wake_up_interruptible(&gpio_wait); } static irqreturn_t dht11_isr(int irq, void *dev_id) { struct gpio_desc *gpio_desc = dev_id; u64 time; /* 1. 记录中断发生的时间 */ time = ktime_get_ns(); g_dht11_irq_time[g_dht11_irq_cnt] = time; /* 2. 累计次数 */ g_dht11_irq_cnt++; /* 3. 次数足够: 解析数据, 放入环形buffer, 唤醒APP */ if (g_dht11_irq_cnt == 84) { del_timer(&gpio_desc->key_timer); //干掉超时限制的定时器 parse_dht11_datas(); } return IRQ_HANDLED; } /* 在入口函数 */ static int __init dht11_init(void) { int err; int i; int count = sizeof(gpios)/sizeof(gpios[0]); printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); for (i = 0; i < count; i++) { gpios[i].irq = gpio_to_irq(gpios[i].gpio); /* 设置DHT11 GPIO引脚的初始状态: output 1 */ err = gpio_request(gpios[i].gpio, gpios[i].name); gpio_direction_output(gpios[i].gpio, 1); gpio_free(gpios[i].gpio); setup_timer(&gpios[i].key_timer, key_timer_expire, (unsigned long)&gpios[i]); //timer_setup(&gpios[i].key_timer, key_timer_expire, 0); //gpios[i].key_timer.expires = ~0; //add_timer(&gpios[i].key_timer); //err = request_irq(gpios[i].irq, dht11_isr, IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING, "100ask_gpio_key", &gpios[i]); } /* 注册file_operations */ major = register_chrdev(0, "100ask_dht11", &dht11_drv); /* /dev/gpio_desc */ gpio_class = class_create(THIS_MODULE, "100ask_dht11_class"); if (IS_ERR(gpio_class)) { printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); unregister_chrdev(major, "100ask_dht11"); return PTR_ERR(gpio_class); } device_create(gpio_class, NULL, MKDEV(major, 0), NULL, "mydht11"); /* /dev/mydht11 */ return err; } /* 有入口函数就应该有出口函数：卸载驱动程序时，就会去调用这个出口函数 */ static void __exit dht11_exit(void) { int i; int count = sizeof(gpios)/sizeof(gpios[0]); printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__); device_destroy(gpio_class, MKDEV(major, 0)); class_destroy(gpio_class); unregister_chrdev(major, "100ask_dht11"); for (i = 0; i < count; i++) { //free_irq(gpios[i].irq, &gpios[i]); //del_timer(&gpios[i].key_timer); } } /* 7. 其他完善：提供设备信息，自动创建设备节点 */ module_init(dht11_init); module_exit(dht11_exit); MODULE_LICENSE("GPL"); - 1
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应用
#include#include #include #include #include #include #include #include static int fd; /* * ./button_test /dev/mydht11 * */ int main(int argc, char **argv) { char buf[2]; int ret; int i; /* 1. 判断参数 */ if (argc != 2) { printf("Usage: %s \n" , argv[0]); return -1; } /* 2. 打开文件 */ fd = open(argv[1], O_RDWR | O_NONBLOCK); if (fd == -1) { printf("can not open file %s\n", argv[1]); return -1; } while (1) { if (read(fd, buf, 2) == 2) printf("get Humidity: %d, Temperature : %d\n", buf[0], buf[1]); else printf("get dht11: -1\n"); sleep(5); } close(fd); return 0; }- 1
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- 原文地址：https://blog.csdn.net/afddasfa/article/details/128031288
