4412驱动-sixth_drv 同步互斥按键驱动

并发-信号量

阻塞与非阻塞

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); 

驱动

#include <linux/module.h>#include <linux/kernel.h>#include <linux/init.h>#include <linux/platform_device.h>#include <linux/fb.h>#include <linux/backlight.h>#include <linux/err.h>#include <linux/pwm.h>#include <linux/slab.h>#include <linux/miscdevice.h>#include <linux/delay.h>#include <linux/timer.h>  /*timer*/#include <asm/uaccess.h>  /*jiffies*/#include <linux/delay.h>#include <linux/interrupt.h> //request_irq#include <mach/irqs.h> //中断号，已包含plat/irqs.h#include <linux/fs.h>#include <linux/device.h> //class_create device_create#include <mach/regs-gpio.h>#include <linux/io.h> //ioremap ioread32 iowrite32#include <linux/sched.h>#include <linux/of.h>  #include <linux/of_device.h>  #include <linux/poll.h>#include <mach/gpio.h>#include <linux/gpio.h>#include <mach/gpio.h>#include <plat/gpio-cfg.h>static struct class *sixthdrv_class;static struct class_device*sixthdrv_class_dev;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 = 0;static struct fasync_struct *button_async;struct led_reg {u32 gpm4con;u8 gpm4dat;};static struct led_reg *led_reg;struct key_reg {u32 gpm4con;u8 gpm4dat;};static struct key_reg *key_reg;struct beep_reg {u32 gpm4con;u8 gpm4dat;};static struct key_reg *beep_reg;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] = {{EXYNOS4_GPX3(2), 0x01},{EXYNOS4_GPX3(3), 0x02},{EXYNOS4_GPX3(4), 0x03},{EXYNOS4_GPX3(5), 0x04},};//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struct semaphore button_lock;/*  * 确定按键值  */static irqreturn_t buttons_irq(int irq, void *dev_id){printk("buttons_irq\n");struct pin_desc * pindesc = (struct pin_desc *)dev_id;unsigned int pinval;//pinval = s3c2410_gpio_getpin(pindesc->pin);//获取按键的键值，因为按键是从该寄存器的第二位开始的，所以需要左移2位，接着与上0xf---1111      //这样，如果用户按下按键，就会返回一个键值保存在key_val这个变量里   pinval = ((key_reg->gpm4dat) >> 2) & 0xf ;  key_val=pinval;printk("buttons_irq :pinval = %d \n",pinval);#if 0if (pinval){/* 松开 */key_val = 0x80 | pindesc->key_val;printk("buttons_irq :key_val = %d\n ",key_val);}else{/* 按下 */key_val = pindesc->key_val;printk("buttons_irq :key_val = %d \n",key_val);}#endif    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 sixth_drv_open(struct inode *inode, struct file *file){int ret;printk("sixth_drv_open\n");#if 0if (!atomic_dec_and_test(&canopen)){atomic_inc(&canopen);return -EBUSY;}#endifif (file->f_flags & O_NONBLOCK){if (down_trylock(&button_lock))return -EBUSY;}else{/* 获取信号量 */down(&button_lock);}//配置4个按键为输入状态，因为按键是从GPXCON[2]开始的，所以要左移8位到对应的位置，将8位以后的16位清0//这样的话就将按键配置的寄存器设置为输入状态了，因为输入是0x0 key_reg->gpm4con  &= ~((0xf<<(2*4)) | (0xf<<(3*4)) | (0xf<<(4*4)) | (0xf<<(5*4)));//先对LED的端口进行清0操作led_reg->gpm4con  &= ~((0xf<<(3*4)) | (0xf<<(2*4)) | (0xf<<(1*4)) | (0xf<<(0*4)));//将4个IO口16位都设置为Output输出状态led_reg->gpm4con |= ((0x1<<(3*4)) | (0x1<<(2*4)) | (0x1<<(1*4)) | (0x1<<(0*4)));//清寄存器 beep_reg->gpm4con &= ~(0xf);//设置io为输出 beep_reg->gpm4con |= (0x1);  ret = request_irq(IRQ_EINT(26), buttons_irq, IRQF_TRIGGER_FALLING , "k1", &pins_desc[0]);ret =request_irq(IRQ_EINT(27), buttons_irq, IRQF_TRIGGER_FALLING , "k2", &pins_desc[1]);ret =request_irq(IRQ_EINT(28), buttons_irq, IRQF_TRIGGER_FALLING , "k3", &pins_desc[2]);ret =request_irq(IRQ_EINT(29), buttons_irq, IRQF_TRIGGER_FALLING , "k4", &pins_desc[3]);return 0;}ssize_t sixth_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos){printk("sixth_drv_read\n");if (size != 1)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, 1);ev_press = 0;return 1;}int sixth_drv_write(struct file *filp , const char __user *buf , size_t count , loff_t *f_pos){int val;printk("fifth_fasync_drv_write\n");//注意，这里是在内核中进行操作，我们需要使用copy_from_user这个函数将用户态的内容拷贝到内核态copy_from_user(&val, buf, count);        switch(val)        {        case 7:printk(KERN_EMERG"led1_on\n");led_reg->gpm4dat &= ~(1<<0) ;printk(KERN_EMERG"beep_on\n");beep_reg->gpm4dat |= 0x1 ;break ;case 11:printk(KERN_EMERG"led2_on\n");led_reg->gpm4dat &= ~(1<<1) ;printk(KERN_EMERG"beep_off\n");beep_reg->gpm4dat &=~0x1 ; //蜂鸣器不响break ;case 13:printk(KERN_EMERG"led3_on\n");led_reg->gpm4dat &= ~(1<<2) ;printk(KERN_EMERG"beep_on\n");beep_reg->gpm4dat |= 0x1 ;break ;case 14:printk(KERN_EMERG"led4_on\n");led_reg->gpm4dat &= ~(1<<3) ;printk(KERN_EMERG"beep_off\n");beep_reg->gpm4dat &=~0x1 ; //蜂鸣器不响break ;        }return 0;}int sixth_drv_close(struct inode *inode, struct file *file){//atomic_inc(&canopen);led_reg->gpm4dat |= ((1<<0) | (1<<1) |(1<<2)| (1<<3)) ; beep_reg->gpm4dat &=~0x1 ; //蜂鸣器不响free_irq(IRQ_EINT(26), &pins_desc[0]);free_irq(IRQ_EINT(27), &pins_desc[1]);free_irq(IRQ_EINT(28), &pins_desc[2]);free_irq(IRQ_EINT(29), &pins_desc[3]);up(&button_lock);return 0;}static unsigned sixth_drv_poll(struct file *file, poll_table *wait){printk("sixth_drv_poll\n");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 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,.write = sixth_drv_write,};int major;static int sixth_drv_init(void){printk("sixth_drv_init\n");major = register_chrdev(0, "sixth_drv", &sencod_drv_fops);sixthdrv_class = class_create(THIS_MODULE, "sixth_drv");sixthdrv_class_dev = device_create(sixthdrv_class, NULL, MKDEV(major, 0), NULL, "chenhaipan"); /* /dev/buttons */led_reg = ioremap(0x110002e0, sizeof(struct led_reg));beep_reg = ioremap(0x114000A0, sizeof(struct beep_reg));key_reg = ioremap(0x11000C60, sizeof(struct key_reg));sema_init(&button_lock, 1);return 0;}static void sixth_drv_exit(void){printk("sixth_drv_exit\n");unregister_chrdev(major, "sixth_drv");device_destroy(sixthdrv_class, MKDEV(major, 0));class_destroy(sixthdrv_class);iounmap(led_reg);iounmap(beep_reg);iounmap(key_reg);}module_init(sixth_drv_init);module_exit(sixth_drv_exit);MODULE_LICENSE("GPL");MODULE_AUTHOR("xiangtan da xue chenhaipan");  MODULE_VERSION("2017.5.4"); 

应用

#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, 1);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/chenhaipan", O_RDWR | O_NONBLOCK);if (fd < 0){printf("can't open!\n");return -1;}//fcntl(fd, F_SETOWN, getpid());//Oflags = fcntl(fd, F_GETFL); //fcntl(fd, F_SETFL, Oflags | FASYNC);while (1){ret = read(fd, &key_val, 1);printf("key_val: 0x%x, ret = %d\n", key_val, ret);write(fd, &key_val,1);sleep(5);}return 0;}

非阻塞方式，没有按键值按下，程序立马返回；
read 返回值 为 -1；

阻塞方式 open

如果不按键，就一直停留，等待，并不运行

总结：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进行操作，
          被挂起的进程进入睡眠状态，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：
          进程不能进行设备操作时并不挂起，他或者放弃，或者不停的查询，直到可以进行操作为止.