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：

 #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>

 static struct class *thirddrv_class;
 static struct class_device    *thirddrv_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，third_drv_read将它清0 */
 static volatile int ev_press = ;

 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[] = {
     {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 = ;                  /* 表示中断发生了 */
     wake_up_interruptible(&button_waitq);   /* 唤醒休眠的进程 */

     return IRQ_RETVAL(IRQ_HANDLED);
 }

 static int third_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[]);
     request_irq(IRQ_EINT2,  buttons_irq, IRQT_BOTHEDGE, "S3", &pins_desc[]);
     request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "S4", &pins_desc[]);
     request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "S5", &pins_desc[]);    

     return ;
 }

 ssize_t third_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
 {
     if (size != )
         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, );
     ev_press = ;

     return ;
 }

 int third_drv_close(struct inode *inode, struct file *file)
 {
     free_irq(IRQ_EINT0, &pins_desc[]);
     free_irq(IRQ_EINT2, &pins_desc[]);
     free_irq(IRQ_EINT11, &pins_desc[]);
     free_irq(IRQ_EINT19, &pins_desc[]);
     return ;
 }

 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    =  third_drv_open,
     .read     =    third_drv_read,
     .release =  third_drv_close,
 };

 int major;
 static int third_drv_init(void)
 {
     major = register_chrdev(, "third_drv", &sencod_drv_fops);

     thirddrv_class = class_create(THIS_MODULE, "third_drv");

     thirddrv_class_dev = class_device_create(thirddrv_class, NULL, MKDEV(major, ), NULL, "buttons"); /* /dev/buttons */

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

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

     return ;
 }

 static void third_drv_exit(void)
 {
     unregister_chrdev(major, "third_drv");
     class_device_unregister(thirddrv_class_dev);
     class_destroy(thirddrv_class);
     iounmap(gpfcon);
     iounmap(gpgcon);
     return ;
 }

 module_init(third_drv_init);

 module_exit(third_drv_exit);

 MODULE_LICENSE("GPL");

driver Code

测试用例：

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

 /* thirddrvtest
   */
 int main(int argc, char **argv)
 {
     int fd;
     unsigned char key_val;

     fd = open("/dev/buttons", O_RDWR);
     if (fd < )
     {
         printf("can't open!\n");
     }

     while ()
     {
         read(fd, &key_val, );
         printf("key_val = 0x%x\n", key_val);
     }

     return ;
 }

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：

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

 /* forthdrvtest
   */
 int main(int argc, char **argv)
 {
     int fd;
     unsigned char key_val;
     int ret;

     struct pollfd fds[];

     fd = open("/dev/buttons", O_RDWR);
     if (fd < )
     {
         printf("can't open!\n");
     }

     fds[].fd     = fd;
     fds[].events = POLLIN;
     while ()
     {
         ret = poll(fds, , );
         if (ret == )
         {
             printf("time out\n");
         }
         else
         {
             read(fd, &key_val, );
             printf("key_val = 0x%x\n", key_val);
         }
     }

     return ;
 }

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

 #include <stdio.h>
 #include <signal.h>
 void my_signal_fun(int signum)
 {
     static int cnt = ;
     printf("signal = %d,%d times",signum,++cnt);
 }

 int main(int argc,char *argv)
 {
     signal(SIGUSR1,my_signal_fun);
     while()
     {
         sleep();
     }
     return ;
 }

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 = ;

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[] = {
    {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 = ;                  /* 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[]);
    request_irq(IRQ_EINT2,  buttons_irq, IRQT_BOTHEDGE, "S3", &pins_desc[]);
    request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "S4", &pins_desc[]);
    request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "S5", &pins_desc[]);    

    return ;
}

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

    return ;
}

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

static unsigned fifth_drv_poll(struct file *file, poll_table *wait)
{
    unsigned int mask = ;
    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\n");
    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(, "fifth_drv", &sencod_drv_fops);

    fifthdrv_class = class_create(THIS_MODULE, "fifth_drv");

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

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

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

    return ;
}

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 ;
}

module_init(fifth_drv_init);

module_exit(fifth_drv_exit);

MODULE_LICENSE("GPL");

driver Code

测试用例：

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

 /* fifthdrvtest
   */
 int fd;

 void my_signal_fun(int signum)
 {
     unsigned char key_val;
     read(fd, &key_val, );
     printf("key_val: 0x%x\n", key_val);
 }

 int main(int argc, char **argv)
 {
     unsigned char key_val;
     int ret;
     int Oflags;

     signal(SIGIO, my_signal_fun);

     fd = open("/dev/buttons", O_RDWR);
     if (fd < )
     {
         printf("can't open!\n");
     }

     fcntl(fd, F_SETOWN, getpid());

     Oflags = fcntl(fd, F_GETFL); 

     fcntl(fd, F_SETFL, Oflags | FASYNC);

     while ()
     {
         sleep();
     }

     return ;
 }

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：

 #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 *sixthdrv_class;
 static struct class_device    *sixthdrv_class_dev;

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

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

 static struct timer_list buttons_timer;

 static DECLARE_WAIT_QUEUE_HEAD(button_waitq);

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

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

 static struct pin_desc *irq_pd;

 //static atomic_t canopen = ATOMIC_INIT(1);     //定义原子变量并初始化为1

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

 /*
   * 确定按键值
   */
 static irqreturn_t buttons_irq(int irq, void *dev_id)
 {
     /* 10ms后启动定时器 */
     irq_pd = (struct pin_desc *)dev_id;
     mod_timer(&buttons_timer, jiffies+HZ/);
     return IRQ_RETVAL(IRQ_HANDLED);
 }

 static int sixth_drv_open(struct inode *inode, struct file *file)
 {
 #if 0
     if (!atomic_dec_and_test(&canopen))
     {
         atomic_inc(&canopen);
         return -EBUSY;
     }
 #endif        

     if (file->f_flags & O_NONBLOCK)
     {
         if (down_trylock(&button_lock))
             return -EBUSY;
     }
     else
     {
         /* 获取信号量 */
         down(&button_lock);
     }

     /* 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[]);
     request_irq(IRQ_EINT2,  buttons_irq, IRQT_BOTHEDGE, "S3", &pins_desc[]);
     request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "S4", &pins_desc[]);
     request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "S5", &pins_desc[]);    

     return ;
 }

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

     if (file->f_flags & O_NONBLOCK)
     {
         if (!ev_press)
             return -EAGAIN;
     }
     else
     {
         /* 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, );
     ev_press = ;

     return ;
 }

 int sixth_drv_close(struct inode *inode, struct file *file)
 {
     //atomic_inc(&canopen);
     free_irq(IRQ_EINT0, &pins_desc[]);
     free_irq(IRQ_EINT2, &pins_desc[]);
     free_irq(IRQ_EINT11, &pins_desc[]);
     free_irq(IRQ_EINT19, &pins_desc[]);
     up(&button_lock);
     return ;
 }

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

     if (ev_press)
         mask |= POLLIN | POLLRDNORM;

     return mask;
 }

 static int sixth_drv_fasync (int fd, struct file *filp, int on)
 {
     printk("driver: sixth_drv_fasync\n");
     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    =  sixth_drv_open,
     .read     =    sixth_drv_read,
     .release =  sixth_drv_close,
     .poll    =  sixth_drv_poll,
     .fasync     =  sixth_drv_fasync,
 };

 int major;

 static void buttons_timer_function(unsigned long data)
 {
     struct pin_desc * pindesc = irq_pd;
     unsigned int pinval;

     if (!pindesc)
         return;

     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 = ;                  /* 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);
 }

 static int sixth_drv_init(void)
 {
     init_timer(&buttons_timer);
     buttons_timer.function = buttons_timer_function;
     //buttons_timer.expires  = 0;
     add_timer(&buttons_timer); 

     major = register_chrdev(, "sixth_drv", &sencod_drv_fops);

     sixthdrv_class = class_create(THIS_MODULE, "sixth_drv");

     /* 为了让mdev根据这些信息来创建设备节点 */
     sixthdrv_class_dev = class_device_create(sixthdrv_class, NULL, MKDEV(major, ), NULL, "buttons"); /* /dev/buttons */

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

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

     return ;
 }

 static void sixth_drv_exit(void)
 {
     unregister_chrdev(major, "sixth_drv");
     class_device_unregister(sixthdrv_class_dev);
     class_destroy(sixthdrv_class);
     iounmap(gpfcon);
     iounmap(gpgcon);
     return ;
 }

 module_init(sixth_drv_init);

 module_exit(sixth_drv_exit);

 MODULE_LICENSE("GPL");

driver Code

测试程序：

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

 /* sixthdrvtest
   */
 int fd;

 void my_signal_fun(int signum)
 {
     unsigned char key_val;
     read(fd, &key_val, );
     printf("key_val: 0x%x\n", key_val);
 }

 int main(int argc, char **argv)
 {
     unsigned char key_val;
     int ret;
     int Oflags;

     //signal(SIGIO, my_signal_fun);

     fd = open("/dev/buttons", O_RDWR);
     if (fd < )
     {
         printf("can't open!\n");
         return -;
     }

     //fcntl(fd, F_SETOWN, getpid());

     //Oflags = fcntl(fd, F_GETFL); 

     //fcntl(fd, F_SETFL, Oflags | FASYNC);

     while ()
     {
         ret = read(fd, &key_val, );
         printf("key_val: 0x%x, ret = %d\n", key_val, ret);
         //sleep(5);
     }

     return ;
 }

驱动：