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linux-2.6内核驱动学习——jz2440之按键

//以下是学习完韦东山老师视屏教程后所做学习记录
中断方式取得按键值：

  1 #include <linux/module.h>
  2 #include <linux/kernel.h>
  3 #include <linux/fs.h>
  4 #include <linux/init.h>
  5 #include <linux/delay.h>
  6 #include <linux/irq.h>
  7 #include <asm/uaccess.h>
  8 #include <asm/irq.h>
  9 #include <asm/io.h>
 10 #include <asm/arch/regs-gpio.h>
 11 #include <asm/hardware.h>
 12 
 13 
 14 static struct class *thirddrv_class;
 15 static struct class_device    *thirddrv_class_dev;
 16 
 17 volatile unsigned long *gpfcon;
 18 volatile unsigned long *gpfdat;
 19 
 20 volatile unsigned long *gpgcon;
 21 volatile unsigned long *gpgdat;
 22 
 23 
 24 static DECLARE_WAIT_QUEUE_HEAD(button_waitq);
 25 
 26 /* 中断事件标志, 中断服务程序将它置1，third_drv_read将它清0 */
 27 static volatile int ev_press = 0;
 28 
 29 
 30 struct pin_desc{
 31     unsigned int pin;
 32     unsigned int key_val;
 33 };
 34 
 35 
 36 /* 键值: 按下时, 0x01, 0x02, 0x03, 0x04 */
 37 /* 键值: 松开时, 0x81, 0x82, 0x83, 0x84 */
 38 static unsigned char key_val;
 39 
 40 struct pin_desc pins_desc[4] = {
 41     {S3C2410_GPF0, 0x01},
 42     {S3C2410_GPF2, 0x02},
 43     {S3C2410_GPG3, 0x03},
 44     {S3C2410_GPG11, 0x04},
 45 };
 46 
 47 
 48 /*
 49   * 确定按键值
 50   */
 51 static irqreturn_t buttons_irq(int irq, void *dev_id)
 52 {
 53     struct pin_desc * pindesc = (struct pin_desc *)dev_id;
 54     unsigned int pinval;
 55     
 56     pinval = s3c2410_gpio_getpin(pindesc->pin);
 57 
 58     if (pinval)
 59     {
 60         /* 松开 */
 61         key_val = 0x80 | pindesc->key_val;
 62     }
 63     else
 64     {
 65         /* 按下 */
 66         key_val = pindesc->key_val;
 67     }
 68 
 69     ev_press = 1;                  /* 表示中断发生了 */
 70     wake_up_interruptible(&button_waitq);   /* 唤醒休眠的进程 */
 71 
 72     
 73     return IRQ_RETVAL(IRQ_HANDLED);
 74 }
 75 
 76 static int third_drv_open(struct inode *inode, struct file *file)
 77 {
 78     /* 配置GPF0,2为输入引脚 */
 79     /* 配置GPG3,11为输入引脚 */
 80     request_irq(IRQ_EINT0,  buttons_irq, IRQT_BOTHEDGE, "S2", &pins_desc[0]);
 81     request_irq(IRQ_EINT2,  buttons_irq, IRQT_BOTHEDGE, "S3", &pins_desc[1]);
 82     request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "S4", &pins_desc[2]);
 83     request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "S5", &pins_desc[3]);    
 84 
 85     return 0;
 86 }
 87 
 88 ssize_t third_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
 89 {
 90     if (size != 1)
 91         return -EINVAL;
 92 
 93     /* 如果没有按键动作, 休眠 */
 94     wait_event_interruptible(button_waitq, ev_press);
 95 
 96     /* 如果有按键动作, 返回键值 */
 97     copy_to_user(buf, &key_val, 1);
 98     ev_press = 0;
 99     
100     return 1;
101 }
102 
103 
104 int third_drv_close(struct inode *inode, struct file *file)
105 {
106     free_irq(IRQ_EINT0, &pins_desc[0]);
107     free_irq(IRQ_EINT2, &pins_desc[1]);
108     free_irq(IRQ_EINT11, &pins_desc[2]);
109     free_irq(IRQ_EINT19, &pins_desc[3]);
110     return 0;
111 }
112 
113 
114 static struct file_operations sencod_drv_fops = {
115     .owner   =  THIS_MODULE,    /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */
116     .open    =  third_drv_open,     
117     .read     =    third_drv_read,       
118     .release =  third_drv_close,       
119 };
120 
121 
122 int major;
123 static int third_drv_init(void)
124 {
125     major = register_chrdev(0, "third_drv", &sencod_drv_fops);
126 
127     thirddrv_class = class_create(THIS_MODULE, "third_drv");
128 
129     thirddrv_class_dev = class_device_create(thirddrv_class, NULL, MKDEV(major, 0), NULL, "buttons"); /* /dev/buttons */
130 
131     gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);
132     gpfdat = gpfcon + 1;
133 
134     gpgcon = (volatile unsigned long *)ioremap(0x56000060, 16);
135     gpgdat = gpgcon + 1;
136 
137     return 0;
138 }
139 
140 static void third_drv_exit(void)
141 {
142     unregister_chrdev(major, "third_drv");
143     class_device_unregister(thirddrv_class_dev);
144     class_destroy(thirddrv_class);
145     iounmap(gpfcon);
146     iounmap(gpgcon);
147     return 0;
148 }
149 
150 
151 module_init(third_drv_init);
152 
153 module_exit(third_drv_exit);
154 
155 MODULE_LICENSE("GPL");

driver Code

测试用例：

 1 #include <sys/types.h>
 2 #include <sys/stat.h>
 3 #include <fcntl.h>
 4 #include <stdio.h>
 5 
 6 /* thirddrvtest 
 7   */
 8 int main(int argc, char **argv)
 9 {
10     int fd;
11     unsigned char key_val;
12     
13     fd = open("/dev/buttons", O_RDWR);
14     if (fd < 0)
15     {
16         printf("can't open!
");
17     }
18 
19     while (1)
20     {
21         read(fd, &key_val, 1);
22         printf("key_val = 0x%x
", key_val);
23     }
24     
25     return 0;
26 }

drvtest Code

以上是采用中断方式的写法。

下面学习了poll机制后，做了改进：

drv Code

测试用例如下：

 1 #include <sys/types.h>
 2 #include <sys/stat.h>
 3 #include <fcntl.h>
 4 #include <stdio.h>
 5 #include <poll.h>
 6 
 7 
 8 /* forthdrvtest 
 9   */
10 int main(int argc, char **argv)
11 {
12     int fd;
13     unsigned char key_val;
14     int ret;
15 
16     struct pollfd fds[1];
17     
18     fd = open("/dev/buttons", O_RDWR);
19     if (fd < 0)
20     {
21         printf("can't open!
");
22     }
23 
24     fds[0].fd     = fd;
25     fds[0].events = POLLIN;
26     while (1)
27     {
28         ret = poll(fds, 1, 5000);
29         if (ret == 0)
30         {
31             printf("time out
");
32         }
33         else
34         {
35             read(fd, &key_val, 1);
36             printf("key_val = 0x%x
", key_val);
37         }
38     }
39     
40     return 0;
41 }

drvtest view

小总结：

　　查询方式：消耗资源，高达90%以上

　　中断：read（）

　　poll：指定超时时间

都是应用程序主动去读。

下面通过异步通知来改进。

先做一个简单的测试

 1 #include <stdio.h>
 2 #include <signal.h>
 3 void my_signal_fun(int signum)
 4 {
 5     static int cnt = 0;
 6     printf("signal = %d,%d times",signum,++cnt);
 7 }
 8 
 9 int main(int argc,char *argv)
10 {
11     signal(SIGUSR1,my_signal_fun);
12     while(1)
13     {
14         sleep(1000);        
15     }
16     return 0;
17 }

signal Code

要点：　　1.注册一个信号处理函数

　　　　　2.谁发？发给谁？怎么发？

目标：按下按键是，驱动程序通知应用程序，

　　　　1、应用程序要注册信号处理函数。

　　　　2、驱动程序发信号给应用程序（应用程序要告诉驱动PID号）

　　　　3、怎么发？

用到signal、fcntl

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <asm/arch/regs-gpio.h>
#include <asm/hardware.h>
#include <linux/poll.h>


static struct class *fifthdrv_class;
static struct class_device    *fifthdrv_class_dev;

volatile unsigned long *gpfcon;
volatile unsigned long *gpfdat;

volatile unsigned long *gpgcon;
volatile unsigned long *gpgdat;


static DECLARE_WAIT_QUEUE_HEAD(button_waitq);

/* 中断事件标志, 中断服务程序将它置1，fifth_drv_read将它清0 */
static volatile int ev_press = 0;

static struct fasync_struct *button_async;


struct pin_desc{
    unsigned int pin;
    unsigned int key_val;
};


/* 键值: 按下时, 0x01, 0x02, 0x03, 0x04 */
/* 键值: 松开时, 0x81, 0x82, 0x83, 0x84 */
static unsigned char key_val;

struct pin_desc pins_desc[4] = {
    {S3C2410_GPF0, 0x01},
    {S3C2410_GPF2, 0x02},
    {S3C2410_GPG3, 0x03},
    {S3C2410_GPG11, 0x04},
};


/*
  * 确定按键值
  */
static irqreturn_t buttons_irq(int irq, void *dev_id)
{
    struct pin_desc * pindesc = (struct pin_desc *)dev_id;
    unsigned int pinval;
    
    pinval = s3c2410_gpio_getpin(pindesc->pin);

    if (pinval)
    {
        /* 松开 */
        key_val = 0x80 | pindesc->key_val;
    }
    else
    {
        /* 按下 */
        key_val = pindesc->key_val;
    }

    ev_press = 1;                  /* 表示中断发生了 */
    wake_up_interruptible(&button_waitq);   /* 唤醒休眠的进程 */
    
    kill_fasync (&button_async, SIGIO, POLL_IN);
    
    return IRQ_RETVAL(IRQ_HANDLED);
}

static int fifth_drv_open(struct inode *inode, struct file *file)
{
    /* 配置GPF0,2为输入引脚 */
    /* 配置GPG3,11为输入引脚 */
    request_irq(IRQ_EINT0,  buttons_irq, IRQT_BOTHEDGE, "S2", &pins_desc[0]);
    request_irq(IRQ_EINT2,  buttons_irq, IRQT_BOTHEDGE, "S3", &pins_desc[1]);
    request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "S4", &pins_desc[2]);
    request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "S5", &pins_desc[3]);    

    return 0;
}

ssize_t fifth_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
{
    if (size != 1)
        return -EINVAL;

    /* 如果没有按键动作, 休眠 */
    wait_event_interruptible(button_waitq, ev_press);

    /* 如果有按键动作, 返回键值 */
    copy_to_user(buf, &key_val, 1);
    ev_press = 0;
    
    return 1;
}


int fifth_drv_close(struct inode *inode, struct file *file)
{
    free_irq(IRQ_EINT0, &pins_desc[0]);
    free_irq(IRQ_EINT2, &pins_desc[1]);
    free_irq(IRQ_EINT11, &pins_desc[2]);
    free_irq(IRQ_EINT19, &pins_desc[3]);
    return 0;
}

static unsigned fifth_drv_poll(struct file *file, poll_table *wait)
{
    unsigned int mask = 0;
    poll_wait(file, &button_waitq, wait); // 不会立即休眠

    if (ev_press)
        mask |= POLLIN | POLLRDNORM;

    return mask;
}

static int fifth_drv_fasync (int fd, struct file *filp, int on)
{
    printk("driver: fifth_drv_fasync
");
    return fasync_helper (fd, filp, on, &button_async);
}


static struct file_operations sencod_drv_fops = {
    .owner   =  THIS_MODULE,    /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */
    .open    =  fifth_drv_open,     
    .read     =    fifth_drv_read,       
    .release =  fifth_drv_close,
    .poll    =  fifth_drv_poll,
    .fasync     =  fifth_drv_fasync,
};


int major;
static int fifth_drv_init(void)
{
    major = register_chrdev(0, "fifth_drv", &sencod_drv_fops);

    fifthdrv_class = class_create(THIS_MODULE, "fifth_drv");

    fifthdrv_class_dev = class_device_create(fifthdrv_class, NULL, MKDEV(major, 0), NULL, "buttons"); /* /dev/buttons */

    gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);
    gpfdat = gpfcon + 1;

    gpgcon = (volatile unsigned long *)ioremap(0x56000060, 16);
    gpgdat = gpgcon + 1;

    return 0;
}

static void fifth_drv_exit(void)
{
    unregister_chrdev(major, "fifth_drv");
    class_device_unregister(fifthdrv_class_dev);
    class_destroy(fifthdrv_class);
    iounmap(gpfcon);
    iounmap(gpgcon);
    return 0;
}


module_init(fifth_drv_init);

module_exit(fifth_drv_exit);

MODULE_LICENSE("GPL");

driver Code

测试用例：

 1 #include <sys/types.h>
 2 #include <sys/stat.h>
 3 #include <fcntl.h>
 4 #include <stdio.h>
 5 #include <poll.h>
 6 #include <signal.h>
 7 #include <sys/types.h>
 8 #include <unistd.h>
 9 #include <fcntl.h>
10 
11 
12 /* fifthdrvtest 
13   */
14 int fd;
15 
16 void my_signal_fun(int signum)
17 {
18     unsigned char key_val;
19     read(fd, &key_val, 1);
20     printf("key_val: 0x%x
", key_val);
21 }
22 
23 int main(int argc, char **argv)
24 {
25     unsigned char key_val;
26     int ret;
27     int Oflags;
28 
29     signal(SIGIO, my_signal_fun);
30     
31     fd = open("/dev/buttons", O_RDWR);
32     if (fd < 0)
33     {
34         printf("can't open!
");
35     }
36 
37     fcntl(fd, F_SETOWN, getpid());
38     
39     Oflags = fcntl(fd, F_GETFL); 
40     
41     fcntl(fd, F_SETFL, Oflags | FASYNC);
42 
43 
44     while (1)
45     {
46         sleep(1000);
47     }
48     
49     return 0;
50 }

drvtest code

fcntl(fd, F_SETOWN, getpid()); //告诉内核，发给谁

Oflags = fcntl(fd, F_GETFL);
fcntl(fd, F_SETFL, Oflags | FASYNC); //改变fasync标记，最终会调用驱动的faync>faync_helper : 初始化/释放fasync_struct

目前，我们这个按键驱动程序已经较完善。

现在我们想让这个驱动同一时间只有一个app可以打开。

如果用一个变量来控制的话，会存在漏洞，分析：

linux是一个多任务的系统，修改一个值的时候有三个过程：1、读出；2、修改；3、写回

修改代码不是一个原子操作，引入原子变量。

笔记如下：

1. 原子操作
原子操作指的是在执行过程中不会被别的代码路径所中断的操作。
常用原子操作函数举例：
atomic_t v = ATOMIC_INIT(0); //定义原子变量v并初始化为0
atomic_read(atomic_t *v); //返回原子变量的值
void atomic_inc(atomic_t *v); //原子变量增加1
void atomic_dec(atomic_t *v); //原子变量减少1
int atomic_dec_and_test(atomic_t *v); //自减操作后测试其是否为0，为0则返回true，否则返回false。

2. 信号量
信号量（semaphore）是用于保护临界区的一种常用方法，只有得到信号量的进程才能执行临界区代码。
当获取不到信号量时，进程进入休眠等待状态。

定义信号量
struct semaphore sem;
初始化信号量
void sema_init (struct semaphore *sem, int val);
void init_MUTEX(struct semaphore *sem);//初始化为0

static DECLARE_MUTEX(button_lock); //定义互斥锁

获得信号量
void down(struct semaphore * sem);
int down_interruptible(struct semaphore * sem);
int down_trylock(struct semaphore * sem);
释放信号量
void up(struct semaphore * sem);

3. 阻塞
阻塞操作
是指在执行设备操作时若不能获得资源则挂起进程，直到满足可操作的条件后再进行操作。
被挂起的进程进入休眠状态，被从调度器的运行队列移走，直到等待的条件被满足。

非阻塞操作
进程在不能进行设备操作时并不挂起，它或者放弃，或者不停地查询，直至可以进行操作为止。

fd = open("...", O_RDWR | O_NONBLOCK);

加上按键防抖动就完美：

  1 #include <linux/module.h>
  2 #include <linux/kernel.h>
  3 #include <linux/fs.h>
  4 #include <linux/init.h>
  5 #include <linux/delay.h>
  6 #include <linux/irq.h>
  7 #include <asm/uaccess.h>
  8 #include <asm/irq.h>
  9 #include <asm/io.h>
 10 #include <asm/arch/regs-gpio.h>
 11 #include <asm/hardware.h>
 12 #include <linux/poll.h>
 13 
 14 
 15 static struct class *sixthdrv_class;
 16 static struct class_device    *sixthdrv_class_dev;
 17 
 18 volatile unsigned long *gpfcon;
 19 volatile unsigned long *gpfdat;
 20 
 21 volatile unsigned long *gpgcon;
 22 volatile unsigned long *gpgdat;
 23 
 24 static struct timer_list buttons_timer;
 25 
 26 
 27 static DECLARE_WAIT_QUEUE_HEAD(button_waitq);
 28 
 29 /* 中断事件标志, 中断服务程序将它置1，sixth_drv_read将它清0 */
 30 static volatile int ev_press = 0;
 31 
 32 static struct fasync_struct *button_async;
 33 
 34 
 35 struct pin_desc{
 36     unsigned int pin;
 37     unsigned int key_val;
 38 };
 39 
 40 
 41 /* 键值: 按下时, 0x01, 0x02, 0x03, 0x04 */
 42 /* 键值: 松开时, 0x81, 0x82, 0x83, 0x84 */
 43 static unsigned char key_val;
 44 
 45 struct pin_desc pins_desc[4] = {
 46     {S3C2410_GPF0, 0x01},
 47     {S3C2410_GPF2, 0x02},
 48     {S3C2410_GPG3, 0x03},
 49     {S3C2410_GPG11, 0x04},
 50 };
 51 
 52 static struct pin_desc *irq_pd;
 53 
 54 //static atomic_t canopen = ATOMIC_INIT(1);     //定义原子变量并初始化为1
 55 
 56 static DECLARE_MUTEX(button_lock);     //定义互斥锁
 57 
 58 /*
 59   * 确定按键值
 60   */
 61 static irqreturn_t buttons_irq(int irq, void *dev_id)
 62 {
 63     /* 10ms后启动定时器 */
 64     irq_pd = (struct pin_desc *)dev_id;
 65     mod_timer(&buttons_timer, jiffies+HZ/100);
 66     return IRQ_RETVAL(IRQ_HANDLED);
 67 }
 68 
 69 static int sixth_drv_open(struct inode *inode, struct file *file)
 70 {
 71 #if 0    
 72     if (!atomic_dec_and_test(&canopen))
 73     {
 74         atomic_inc(&canopen);
 75         return -EBUSY;
 76     }
 77 #endif        
 78 
 79     if (file->f_flags & O_NONBLOCK)
 80     {
 81         if (down_trylock(&button_lock))
 82             return -EBUSY;
 83     }
 84     else
 85     {
 86         /* 获取信号量 */
 87         down(&button_lock);
 88     }
 89 
 90     /* 配置GPF0,2为输入引脚 */
 91     /* 配置GPG3,11为输入引脚 */
 92     request_irq(IRQ_EINT0,  buttons_irq, IRQT_BOTHEDGE, "S2", &pins_desc[0]);
 93     request_irq(IRQ_EINT2,  buttons_irq, IRQT_BOTHEDGE, "S3", &pins_desc[1]);
 94     request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "S4", &pins_desc[2]);
 95     request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "S5", &pins_desc[3]);    
 96 
 97     return 0;
 98 }
 99 
100 ssize_t sixth_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
101 {
102     if (size != 1)
103         return -EINVAL;
104 
105     if (file->f_flags & O_NONBLOCK)
106     {
107         if (!ev_press)
108             return -EAGAIN;
109     }
110     else
111     {
112         /* 如果没有按键动作, 休眠 */
113         wait_event_interruptible(button_waitq, ev_press);
114     }
115 
116     /* 如果有按键动作, 返回键值 */
117     copy_to_user(buf, &key_val, 1);
118     ev_press = 0;
119     
120     return 1;
121 }
122 
123 
124 int sixth_drv_close(struct inode *inode, struct file *file)
125 {
126     //atomic_inc(&canopen);
127     free_irq(IRQ_EINT0, &pins_desc[0]);
128     free_irq(IRQ_EINT2, &pins_desc[1]);
129     free_irq(IRQ_EINT11, &pins_desc[2]);
130     free_irq(IRQ_EINT19, &pins_desc[3]);
131     up(&button_lock);
132     return 0;
133 }
134 
135 static unsigned sixth_drv_poll(struct file *file, poll_table *wait)
136 {
137     unsigned int mask = 0;
138     poll_wait(file, &button_waitq, wait); // 不会立即休眠
139 
140     if (ev_press)
141         mask |= POLLIN | POLLRDNORM;
142 
143     return mask;
144 }
145 
146 static int sixth_drv_fasync (int fd, struct file *filp, int on)
147 {
148     printk("driver: sixth_drv_fasync
");
149     return fasync_helper (fd, filp, on, &button_async);
150 }
151 
152 
153 static struct file_operations sencod_drv_fops = {
154     .owner   =  THIS_MODULE,    /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */
155     .open    =  sixth_drv_open,     
156     .read     =    sixth_drv_read,       
157     .release =  sixth_drv_close,
158     .poll    =  sixth_drv_poll,
159     .fasync     =  sixth_drv_fasync,
160 };
161 
162 
163 int major;
164 
165 static void buttons_timer_function(unsigned long data)
166 {
167     struct pin_desc * pindesc = irq_pd;
168     unsigned int pinval;
169 
170     if (!pindesc)
171         return;
172     
173     pinval = s3c2410_gpio_getpin(pindesc->pin);
174 
175     if (pinval)
176     {
177         /* 松开 */
178         key_val = 0x80 | pindesc->key_val;
179     }
180     else
181     {
182         /* 按下 */
183         key_val = pindesc->key_val;
184     }
185 
186     ev_press = 1;                  /* 表示中断发生了 */
187     wake_up_interruptible(&button_waitq);   /* 唤醒休眠的进程 */
188     
189     kill_fasync (&button_async, SIGIO, POLL_IN);
190 }
191 
192 
193 static int sixth_drv_init(void)
194 {
195     init_timer(&buttons_timer);
196     buttons_timer.function = buttons_timer_function;
197     //buttons_timer.expires  = 0;
198     add_timer(&buttons_timer); 
199 
200     major = register_chrdev(0, "sixth_drv", &sencod_drv_fops);
201 
202     sixthdrv_class = class_create(THIS_MODULE, "sixth_drv");
203 
204     /* 为了让mdev根据这些信息来创建设备节点 */
205     sixthdrv_class_dev = class_device_create(sixthdrv_class, NULL, MKDEV(major, 0), NULL, "buttons"); /* /dev/buttons */
206 
207     gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);
208     gpfdat = gpfcon + 1;
209 
210     gpgcon = (volatile unsigned long *)ioremap(0x56000060, 16);
211     gpgdat = gpgcon + 1;
212 
213     return 0;
214 }
215 
216 static void sixth_drv_exit(void)
217 {
218     unregister_chrdev(major, "sixth_drv");
219     class_device_unregister(sixthdrv_class_dev);
220     class_destroy(sixthdrv_class);
221     iounmap(gpfcon);
222     iounmap(gpgcon);
223     return 0;
224 }
225 
226 
227 module_init(sixth_drv_init);
228 
229 module_exit(sixth_drv_exit);
230 
231 MODULE_LICENSE("GPL");

driver Code

测试程序：

 1 #include <sys/types.h>
 2 #include <sys/stat.h>
 3 #include <fcntl.h>
 4 #include <stdio.h>
 5 #include <poll.h>
 6 #include <signal.h>
 7 #include <sys/types.h>
 8 #include <unistd.h>
 9 #include <fcntl.h>
10 
11 
12 /* sixthdrvtest 
13   */
14 int fd;
15 
16 void my_signal_fun(int signum)
17 {
18     unsigned char key_val;
19     read(fd, &key_val, 1);
20     printf("key_val: 0x%x
", key_val);
21 }
22 
23 int main(int argc, char **argv)
24 {
25     unsigned char key_val;
26     int ret;
27     int Oflags;
28 
29     //signal(SIGIO, my_signal_fun);
30     
31     fd = open("/dev/buttons", O_RDWR);
32     if (fd < 0)
33     {
34         printf("can't open!
");
35         return -1;
36     }
37 
38     //fcntl(fd, F_SETOWN, getpid());
39     
40     //Oflags = fcntl(fd, F_GETFL); 
41     
42     //fcntl(fd, F_SETFL, Oflags | FASYNC);
43 
44 
45     while (1)
46     {
47         ret = read(fd, &key_val, 1);
48         printf("key_val: 0x%x, ret = %d
", key_val, ret);
49         //sleep(5);
50     }
51     
52     return 0;
53 }

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原文地址：https://www.cnblogs.com/jason-linux/p/10280844.html