嵌入式Linux驱动学习之路(十四)按键驱动-同步、互斥、阻塞

目的：同一个时刻，只能有一个应用程序打开我们的驱动程序。

①原子操作：

v = ATOMIC_INIT( i ) 　　定义原子变量v并初始化为i

atomic_read(v)        返回原子变量的值
atomic_set(v,i)        设置原子变量的值      

atomic_inc_and_test(v)     自加后和测试是否为0  为0则返回true

atomic_dec_and_test(v)     自减后和测试是否为0  为0则返回true

atomic_inc(v)　　　　　　自加
#atomic_dec(v)　　　　　自减

驱动代码：

#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/spinlock.h>
#include <linux/errno.h>
#include <linux/random.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/wait.h>
#include <linux/mutex.h>
#include <linux/io.h>
#include <asm/irq.h>
#include <linux/irq.h>
#include <linux/fs.h>
#include <asm/arch/regs-gpio.h>
#include <linux/interrupt.h>
#include <linux/poll.h>


static struct class *key_class;     //创建类
static struct class_device *key_class_devs;   //创建类对应的设备


struct pin_desc{
    unsigned int pin;
    unsigned int key_val;
};
struct pin_desc pins_desc[4] = {
    {S3C2410_GPF0,0X01},
    {S3C2410_GPF2,0X02},
    {S3C2410_GPG3,0X03},
    {S3C2410_GPG11,0X04},
};
unsigned char keyvals=0;

static volatile int ev_press = 0;
static DECLARE_WAIT_QUEUE_HEAD(button_waitq);

static struct fasync_struct *key_async_queue;

atomic_t canopen = ATOMIC_INIT(1); 

static irqreturn_t keys_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)
    {
        keyvals = pindesc->key_val|0x80;
    }
    else
    {
        keyvals = pindesc->key_val;
    }
    ev_press = 1;
    wake_up_interruptible(&button_waitq);

    kill_fasync (&key_async_queue, SIGIO, POLL_IN);

    return IRQ_HANDLED;
}


int key_open(struct inode *inode, struct file *fp)
{
    if(!atomic_dec_and_test(&canopen))  //if --canopen==0 return ture  /*自减后和0相比 如果等于0 则返回true*/
    {
        atomic_inc(&canopen);
        return -EBUSY;
    }

    request_irq( IRQ_EINT0, keys_irq, IRQT_BOTHEDGE, "key2", &pins_desc[0]);
    request_irq( IRQ_EINT2, keys_irq, IRQT_BOTHEDGE, "key3", &pins_desc[1]);
    request_irq( IRQ_EINT11, keys_irq, IRQT_BOTHEDGE, "key4", &pins_desc[2]);
    request_irq( IRQ_EINT19, keys_irq, IRQT_BOTHEDGE, "key5", &pins_desc[3]);
    return 0;
}

ssize_t key_read(struct file *fp, char __user *buff, size_t count, loff_t *offp){

    if(count != 1)
    {
        return -EINVAL;
    }
    wait_event_interruptible(button_waitq,ev_press);
    
    copy_to_user(buff,&keyvals,1);
    ev_press = 0;
    return 0;
}

ssize_t key_write(struct file *fp, const char __user *buf, size_t count, loff_t *ppos){
}

int key_close(struct inode *inode, struct file *file)
{
    atomic_inc(&canopen);
    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]);
}

static unsigned int key_poll(struct file *file, struct poll_table_struct *wait)
{
    unsigned int mask = 0;
    poll_wait(file, &button_waitq,wait);
    if(ev_press)
        mask |= POLLIN|POLLRDNORM;
    return mask;
}

static int key_fsync (int fd, struct file *filp, int on)
{
    printk("ok
");
    return fasync_helper (fd, filp, on, &key_async_queue);
}

struct file_operations led_fops={
    .owner = THIS_MODULE,
    .open = key_open,
    .write  = key_write,
    .read   = key_read,
    .release = key_close,
    .poll = key_poll,
    .fasync = key_fsync,
};

int major;
static int key_init(void)
{
    major = register_chrdev( 0,"key_drv", &led_fops );
    key_class = class_create(THIS_MODULE,"key_class");
    key_class_devs = class_device_create(key_class,NULL,MKDEV(major,0),NULL,"my_keys");
    
    printk("key install Module
");
    return 0;
}

static void key_exit(void)
{
    unregister_chrdev( major, "key_drv" );
    class_device_unregister(key_class_devs);
    class_destroy(key_class);
    printk("key Module exit
");
}

module_init(key_init);
module_exit(key_exit);
MODULE_LICENSE("GPL");

信号量：

#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/spinlock.h>
#include <linux/errno.h>
#include <linux/random.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/wait.h>
#include <linux/mutex.h>
#include <linux/io.h>
#include <asm/irq.h>
#include <linux/irq.h>
#include <linux/fs.h>
#include <asm/arch/regs-gpio.h>
#include <linux/interrupt.h>
#include <linux/poll.h>


static struct class *key_class;     //创建类
static struct class_device *key_class_devs;   //创建类对应的设备


struct pin_desc{
    unsigned int pin;
    unsigned int key_val;
};
struct pin_desc pins_desc[4] = {
    {S3C2410_GPF0,0X01},
    {S3C2410_GPF2,0X02},
    {S3C2410_GPG3,0X03},
    {S3C2410_GPG11,0X04},
};
unsigned char keyvals=0;

static volatile int ev_press = 0;
static DECLARE_WAIT_QUEUE_HEAD(button_waitq);

static struct fasync_struct *key_async_queue;

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

static irqreturn_t keys_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)
    {
        keyvals = pindesc->key_val|0x80;
    }
    else
    {
        keyvals = pindesc->key_val;
    }
    ev_press = 1;
    wake_up_interruptible(&button_waitq);

    kill_fasync (&key_async_queue, SIGIO, POLL_IN);

    return IRQ_HANDLED;
}


int key_open(struct inode *inode, struct file *fp)
{
    /*获取信号量*/
    down(&canopen);　　　　　　//如果设备已经被打开，那么程序将会一直停在这里知道信号量被释放。

    request_irq( IRQ_EINT0, keys_irq, IRQT_BOTHEDGE, "key2", &pins_desc[0]);
    request_irq( IRQ_EINT2, keys_irq, IRQT_BOTHEDGE, "key3", &pins_desc[1]);
    request_irq( IRQ_EINT11, keys_irq, IRQT_BOTHEDGE, "key4", &pins_desc[2]);
    request_irq( IRQ_EINT19, keys_irq, IRQT_BOTHEDGE, "key5", &pins_desc[3]);
    return 0;
}

ssize_t key_read(struct file *fp, char __user *buff, size_t count, loff_t *offp){

    if(count != 1)
    {
        return -EINVAL;
    }
    wait_event_interruptible(button_waitq,ev_press);
    
    copy_to_user(buff,&keyvals,1);
    ev_press = 0;
    return 0;
}

ssize_t key_write(struct file *fp, const char __user *buf, size_t count, loff_t *ppos){
}

int key_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]);
    up(&canopen);
}

static unsigned int key_poll(struct file *file, struct poll_table_struct *wait)
{
    unsigned int mask = 0;
    poll_wait(file, &button_waitq,wait);
    if(ev_press)
        mask |= POLLIN|POLLRDNORM;
    return mask;
}

static int key_fsync (int fd, struct file *filp, int on)
{
    printk("ok
");
    return fasync_helper (fd, filp, on, &key_async_queue);
}

struct file_operations led_fops={
    .owner = THIS_MODULE,
    .open = key_open,
    .write  = key_write,
    .read   = key_read,
    .release = key_close,
    .poll = key_poll,
    .fasync = key_fsync,
};

int major;
static int key_init(void)
{
    major = register_chrdev( 0,"key_drv", &led_fops );
    key_class = class_create(THIS_MODULE,"key_class");
    key_class_devs = class_device_create(key_class,NULL,MKDEV(major,0),NULL,"my_keys");
    
    printk("key install Module
");
    return 0;
}

static void key_exit(void)
{
    unregister_chrdev( major, "key_drv" );
    class_device_unregister(key_class_devs);
    class_destroy(key_class);
    printk("key Module exit
");
}



module_init(key_init);
module_exit(key_exit);
MODULE_LICENSE("GPL");

阻塞：分为阻塞和非阻塞

　　如何分辨阻塞和非阻塞呢？则需要在打开设备文件的时候传入一个参数

#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/spinlock.h>
#include <linux/errno.h>
#include <linux/random.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/wait.h>
#include <linux/mutex.h>
#include <linux/io.h>
#include <asm/irq.h>
#include <linux/irq.h>
#include <linux/fs.h>
#include <asm/arch/regs-gpio.h>
#include <linux/interrupt.h>
#include <linux/poll.h>


static struct class *key_class;     //创建类
static struct class_device *key_class_devs;   //创建类对应的设备


struct pin_desc{
    unsigned int pin;
    unsigned int key_val;
};
struct pin_desc pins_desc[4] = {
    {S3C2410_GPF0,0X01},
    {S3C2410_GPF2,0X02},
    {S3C2410_GPG3,0X03},
    {S3C2410_GPG11,0X04},
};
unsigned char keyvals=0;

static volatile int ev_press = 0;
static DECLARE_WAIT_QUEUE_HEAD(button_waitq);

static struct fasync_struct *key_async_queue;

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

static irqreturn_t keys_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)
    {
        keyvals = pindesc->key_val|0x80;
    }
    else
    {
        keyvals = pindesc->key_val;
    }
    ev_press = 1;
    wake_up_interruptible(&button_waitq);

    kill_fasync (&key_async_queue, SIGIO, POLL_IN);

    return IRQ_HANDLED;
}


int key_open(struct inode *inode, struct file *fp)
{
    /*获取信号量*/
    if( fp->f_flags & O_NONBLOCK )
    {
        if(down_trylock(&canopen))
            return -EBUSY;
    }
    else
    {
        down(&canopen);
    }
    request_irq( IRQ_EINT0, keys_irq, IRQT_BOTHEDGE, "key2", &pins_desc[0]);
    request_irq( IRQ_EINT2, keys_irq, IRQT_BOTHEDGE, "key3", &pins_desc[1]);
    request_irq( IRQ_EINT11, keys_irq, IRQT_BOTHEDGE, "key4", &pins_desc[2]);
    request_irq( IRQ_EINT19, keys_irq, IRQT_BOTHEDGE, "key5", &pins_desc[3]);
    return 0;
}

ssize_t key_read(struct file *fp, char __user *buff, size_t count, loff_t *offp){

    if(fp->f_flags & O_NONBLOCK )
    {
        if(!ev_press)
            return -EAGAIN;
    }
    else
    {
        wait_event_interruptible(button_waitq,ev_press);
    }
    if(count != 1)
    {
        return -EINVAL;
    }
    
    copy_to_user(buff,&keyvals,1);
    ev_press = 0;
    return 0;
}

ssize_t key_write(struct file *fp, const char __user *buf, size_t count, loff_t *ppos){
}

int key_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]);
    up(&canopen);
}

static unsigned int key_poll(struct file *file, struct poll_table_struct *wait)
{
    unsigned int mask = 0;
    poll_wait(file, &button_waitq,wait);
    if(ev_press)
        mask |= POLLIN|POLLRDNORM;
    return mask;
}

static int key_fsync (int fd, struct file *filp, int on)
{
    printk("ok
");
    return fasync_helper (fd, filp, on, &key_async_queue);
}

struct file_operations led_fops={
    .owner = THIS_MODULE,
    .open = key_open,
    .write  = key_write,
    .read   = key_read,
    .release = key_close,
    .poll = key_poll,
    .fasync = key_fsync,
};

int major;
static int key_init(void)
{
    major = register_chrdev( 0,"key_drv", &led_fops );
    key_class = class_create(THIS_MODULE,"key_class");
    key_class_devs = class_device_create(key_class,NULL,MKDEV(major,0),NULL,"my_keys");
    
    printk("key install Module
");
    return 0;
}

static void key_exit(void)
{
    unregister_chrdev( major, "key_drv" );
    class_device_unregister(key_class_devs);
    class_destroy(key_class);
    printk("key Module exit
");
}



module_init(key_init);
module_exit(key_exit);
MODULE_LICENSE("GPL");

阻塞测试文件：

#include <stdio.h>
#include <signal.h>
#include <fcntl.h>
#include <unistd.h>

int fd;

static char key_val;
int main( int argc, char **argv )
{
    int oflags;
    fd = open("/dev/my_keys",O_RDWR|O_NONBLOCK);　　/* O_NONBLOCK为非阻塞*/
   
    if(fd<0)
    {
        printf("open failed
");
        return 0;
    }

    while(1)
    {
        read(fd,&key_val,1);
        printf("key_val:%d
",key_val);
        sleep(1);
    }


    return 0;
}

完

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原文地址：https://www.cnblogs.com/ynxf/p/6000644.html