/***********************************************************************************
 *                    
 *               spinlock,semaphore,atomic,mutex,completion,interrupt
 *
 *   声明:
 *       1. 本系列文档是在vim下编辑,请尽量是用vim来阅读,在其它编辑器下可能会
 *         不对齐,从而影响阅读.
 *       2. 本文中有些源代码没有全部帖出来,主要是因为篇幅太大的原因;
 *       3. 基于2中的原因,本文借鉴了python中的缩进代码风格进行代码的体现:
 *           1. 有些代码中的"..."代表省略了不影响阅读的代码;
 *           2. 如下代码缩进代表在一个函数内部的代码,至于在什么函数里,不影响阅读:
 *               ... //省略代码
 *               struct test_s {
 *               };
 *               ... //省略代码
 *
 *                   //进入临界区之前加锁     }
 *                   spin_lock(&p->lock);     | 
 *                                            |   |
 *                   /* 有效代码 */           |-->|采用缩进,代表在一个函数内
 *                                            |   |的代码
 *                   //出临界区之后解锁       |
 *                   spin_unlock(&p->lock);   }
 *
 *               ... //省略代码                                
 *               int __init test_init(void)
 *               {   
 *                   ... //省略代码
 *               }  
 *               ... //省略代码
 *
 *
 *                                          2015-3-13 阴 深圳 尚观 Var 曾剑锋
 **********************************************************************************/

                        \\\\\\\\--*目录*--////////
                        |  一. spinlock接口;     
                        |  二. semaphore接口;    
                        |  三. atomic接口;       
                        |  四. mutex接口;        
                        |  五. completion接口;   
                        |  六. interrupt接口;    
                        |  七. 按键驱动大致写法;
                        |  八. 测试按键驱动;     
                        \\\\\\\\\\\\//////////////


一. spinlock接口:
    1. 声明:       spinlock_t lock;
    2. 初始化:     spin_lock_init(&test.lock);
    3. 获取自旋锁: spin_lock(&p->lock);
    4. 释放自旋锁: spin_unlock(&p->lock);
    5. spin_lock接口使用Demo:
        ...
        struct test_s {
            struct file_operations fops;
            spinlock_t lock;
            int major;
        };
        ...
            //进入临界区之前加锁
            spin_lock(&p->lock);
            for(i = 0; i < 3; i++)
            {
                printk("count = %d, %s", cnt++, kbuf);
                /*msleep(10);*/
                mdelay(10);
            }
            //出临界区之后解锁
            spin_unlock(&p->lock);
        ...
        int __init test_init(void)
        {   
            int ret;
            // 初始化spin_lock   
            spin_lock_init(&test.lock);
        
            ret = register_chrdev(test.major,
                    DEV_NAME, &test.fops);
            if(ret > 0)
            {
                test.major = ret;
                printk("major = %d\n", test.major);
                ret = 0;
            }
        
            return ret;
        }  
        ...

二. semaphore接口:
    1. 定义: struct semaphore sem;
    2. 定义一个信号量,并初始化: DEFINE_SEMAPHORE(name);
    3. 初始化: sema_init(&test.sem, 1);
    4. 3种获取信号量: 
        1. down(&p->sem);
        2. down_interruptible(&p->sem);
        3. down_trylock(&p->sem);
    5. 释放信号量: up(&p->sem);
    6. semaphore接口使用Demo:
        ...
        struct test_s {
            struct file_operations fops;
            /**
             * spinlock_t lock;
             * volatile int count;
             */
            struct semaphore sem;
            int major;
        };
        ...
            /**
             * spin_lock(&p->lock);
             * if(p->count <= 0)
             * {
             *     spin_unlock(&p->lock);
             *     return -EAGAIN;
             * }
             * p->count--;
             * spin_unlock(&p->lock);
             */
        
            //加不了锁,睡眠等待
            /*down(&p->sem);*/
        
            if(down_trylock(&p->sem))
                return -EAGAIN;
        
            for(i = 0; i < 3; i++)
            {
                printk("count = %d, %s", cnt++, kbuf);
                msleep(10);
            }
        
            up(&p->sem);
        
            /**
             * spin_lock(&p->lock);
             * p->count++;
             * spin_unlock(&p->lock);
             */
        ...
        int __init test_init(void)
        {
            int ret;
        
            /**
             * spin_lock_init(&test.lock);
             * test.count = 1;
             */
        
            sema_init(&test.sem, 1);
        
            ret = register_chrdev(test.major,
                    DEV_NAME, &test.fops);
            if(ret > 0)
            {
                test.major = ret;
                printk("major = %d\n", test.major);
                ret = 0;
            }
        
            return ret;
        }
        ...

三. atomic接口:
    1. 头文件:   linux-3.5/include/linux/atomic.h
    2. 声明定义: atomic_t val; atomic_t *v = &val;
    3. 读取原子变量的值:   atomic_read(v);
    4. 修改原子变量的值:   atomic_set(v, i);
    5. 原子变量自加1:      atomic_inc(v); --> v += 1;
    6. 原子变量自减1:      atomic_dec(v); --> v -= 1;
    7. 原子变量自加1并检测是否为0:       atomic_inc_and_test(v); v += 1,判断结果是否为0
    8. 原子变量自减1并检测是否为0:       atomic_dec_and_test(v); v -= 1,判断结果是否为0
    9. 原子变量自加1并返回原子变量的值:  atomic_inc_return(v)
    10. 原子变量自减1并返回原子变量的值: atomic_dec_return(v)
    11. 比较变量i和原子变量的值是否相等: atomic_sub_and_test(i, v)
    12. atomic接口使用Demo:
        ...
        struct test_s {
            struct file_operations fops;
            atomic_t v;
            int major;
        };
        typedef struct test_s test_t;
        
        static int test_open(struct inode *inode, struct file *file)
        {
            test_t *p;
            p = container_of(file->f_op, test_t, fops);
        
            file->private_data = p;
        
            if(!atomic_dec_and_test(&p->v))
            {
                atomic_inc(&p->v);
                return -EAGAIN;
            }
        
            printk("Open.\n");
        
            return 0;
        }
        
        static int test_close(struct inode *inode, struct file *file)
        {
            test_t *p = file->private_data;
        
            printk("Close.\n");
            atomic_inc(&p->v);
        
            return 0;
        }
        ...
        int __init test_init(void)
        {
            int ret;
        
            atomic_set(&test.v, 1);
        
            ret = register_chrdev(test.major,
                    DEV_NAME, &test.fops);
            if(ret > 0)
            {
                test.major = ret;
                printk("major = %d\n", test.major);
                ret = 0;
            }
        
            return ret;
        }
        ...

四. mutex接口:
    1. 定义: struct mutex lock;
    2. 定义一个互斥锁,并初始化: DEFINE_MUTEX(mutexname);
    3. 初始化: mutex_init(&lock);
    4. 3种加锁方式:
        1. mutex_lock(&lock);
        2. mutex_lock_interruptible(&lock);
        3. mutex_trylock(&lock);
    5. 解锁: mutex_unlock(&lock);
    6. mutex接口使用Demo:
        ...
        struct test_s {
            struct file_operations fops;
            /*struct semaphore sem;*/
            struct mutex lock;
            int major;
        };
        typedef struct test_s test_t;
        ...
            /*mutex_lock(&p->lock);*/
        
            /*
             *if(mutex_lock_interruptible(&p->lock))
             *    return -EINTR;
             */
        
            if(!mutex_trylock(&p->lock))
                return -EAGAIN;
        
            for(i = 0; i < 3; i++)
            {
                printk("count = %d, %s", cnt++, kbuf);
                msleep(10);
            }
        
            mutex_unlock(&p->lock);
        ...
        int __init test_init(void)
        {
            int ret;
        
            mutex_init(&test.lock);
        
            ret = register_chrdev(test.major, DEV_NAME, &test.fops);
            if(ret > 0)
            {
                test.major = ret;
                printk("major = %d\n", test.major);
                ret = 0;
            }
        
            return ret;
        }

五. completion接口:
    1. 定义: struct completion com;
    2. 定义一个完成量,并初始化: DECLARE_COMPLETION(work)
    3. 初始化: init_completion(&com);
    4. 2种等待完成: 
        1. wait_for_completion(&com);
        2. wait_for_completion_interruptible(&com);
    5. 2种通知完成量:
        1. complete(&com);
        2. complete_all(&com);
    6. mutex接口使用Demo:
        ...
        struct test_s {
            struct file_operations fops;
            struct completion com;
            int major;
        };
        typedef struct test_s test_t;
        ...
        static ssize_t test_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
        {
            test_t *p = file->private_data;
            
            //在完成量com上阻塞
            /*wait_for_completion(&p->com);*/
        
            if(wait_for_completion_interruptible(&p->com))
                return -ERESTARTSYS;
                
            printk("Read data.\n");
        
        
            return count;
        }
        
        static ssize_t test_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
        {
            test_t *p = file->private_data;
            
            printk("Write data.\n");
            
            /*complete(&p->com);*/
            
            //通知所有阻塞的进程
            complete_all(&p->com);
            
            return count;
        }  
        ...
        int __init test_init(void)
        {
            int ret;
        
            init_completion(&test.com);
            ret = register_chrdev(test.major,
                                  DEV_NAME, &test.fops);
            if(ret > 0)
            {
                test.major = ret;
                printk("major = %d\n", test.major);
                ret = 0;
            }
        
            return ret;
        }
        ...
六. interrupt接口:
    1. 查看系统中断处理信息: cat /proc/interrupts
    2. 申请并注册中断处理函数:
        static inline int __must_check request_irq( unsigned int irq, irq_handler_t handler,
                                      unsigned long flags, const char *name, void *dev_data);
    3. 释放中断,并取消中断处理函数:
        void free_irq(unsigned int irq, void *dev_data);
    4. 代码执行环境:
        1. 中断上下文:         in_interrupt(); ---> 判断执行环境是否是中断上下文
            1. 软中断上下文:   in_softirq();   ---> 判断执行环境是否是soft irq
            2. 外部中断上下文: in_irq();       ---> 判断执行环境是否是硬件中断处理环境
        2. 进程上下文.
    5. 共享中断方法:
        1. request_irq()指定共享标志 IRQF_SHARED;
        2. request_irq()最后一个参数不能传递NULL,传递当前驱动全局变量地址;
    6. 将系统gpio编号转换成对应的外部中断: gpio_to_irq();
    7. spinlock中断中使用Demo:
        ...
        struct test_s {
            struct file_operations fops;
            spinlock_t lock;
            int major;
        };
        typedef struct test_s test_t;
        ...
        int critical(const char *s, spinlock_t *lock)
        {
            int i;
            unsigned long flag;
            static int cnt = 0;
        
            /*spin_lock(lock);*/
            /*local_irq_disable();*/
            /*local_irq_save(flag);*/
            /*spin_lock_irq(lock);*/
            spin_lock_irqsave(lock, flag);
        
            for(i = 0; i < 3; i++)
            {
                printk("count = %d, %s", cnt++, s);
                mdelay(1000);
            }
        
            spin_unlock_irqrestore(lock, flag);
            /*spin_unlock_irq(lock);*/
            /*local_irq_restore(flag);*/
            /*local_irq_enable();*/
            /*spin_unlock(lock);*/
        
            return 0;
        }
        
        static irqreturn_t irq_handler(int irq, void *arg)
        {
            test_t *p = arg;
        
            critical("irq\n", &p->lock);
        
            return IRQ_HANDLED;
        }
        
        static ssize_t test_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
        {
            int ret;
            char kbuf[count + 1];
            test_t *p = file->private_data;
        
            ret = copy_from_user(kbuf, buf, count);
            if(ret)
                return -EFAULT;
            kbuf[count] = '\0';
        
            if(critical(kbuf, &p->lock))
                return -EAGAIN;
        
            return count;
        }
        ...
        int __init test_init(void)
        {
            int ret;
        
            spin_lock_init(&test.lock);
        
            ret = register_chrdev(test.major,
                    DEV_NAME, &test.fops);
            if(ret > 0)
            {
                test.major = ret;
                printk("major = %d\n", test.major);
                ret = 0;
            }
        
            ret = request_irq(IRQ_EINT(26), irq_handler,
                              IRQF_TRIGGER_FALLING,
                              "key1", &test);
            if(ret)
                unregister_chrdev(test.major, DEV_NAME);
        
            return ret;
        }
        ...

七. 按键驱动大致写法:
    #include <linux/module.h>
    #include <linux/fs.h>
    #include <linux/gpio.h>
    #include <linux/delay.h>
    #include <linux/interrupt.h>
    #include <linux/uaccess.h>
    #include <linux/sched.h>
    
    #define DEV_NAME    "test"
    
    struct timer_list timer;
    struct btn_desc {
        int gpio;
        int num;
        char *name;
    };
    
    int ev_key = 0;
    char key_state[] = {0, 0, 0, 0};
    DECLARE_WAIT_QUEUE_HEAD(wq);
    
    struct btn_desc btn[] = {
        { EXYNOS4_GPX3(2), 0, "key1" },
        { EXYNOS4_GPX3(3), 1, "key2" },
        { EXYNOS4_GPX3(4), 2, "key3" },
        { EXYNOS4_GPX3(5), 3, "key4" }
    };
    
    void timer_main(unsigned long data)
    {
        ev_key = 1;
        wake_up_interruptible(&wq);
        printk("timer_main.\n");
    }
    
    static irqreturn_t irq_handler(int irq, void *arg)
    {
        struct btn_desc *key = arg;
    
        key_state[key->num] = 1;
    
        mod_timer(&timer, jiffies + 20);
    
        return IRQ_HANDLED;
    }
    
    static int test_open(struct inode *inode, struct file *file)
    {
        int i, irq, ret;
    
        for(i = 0; i < ARRAY_SIZE(btn); i++)
        {
            //irq = IRQ_EINT(26+i); //irq可以通过这种方法获得
            irq = gpio_to_irq(btn[i].gpio);
            ret = request_irq(irq, irq_handler, IRQF_TRIGGER_FALLING | IRQF_SHARED,
                        btn[i].name, &btn[i]);
            if(ret)
                break;
        }
    
        if(ret)
        {
            for(--i; i >= 0; i--)
            {
                irq = gpio_to_irq(btn[i].gpio);
                free_irq(irq, &btn[i]);
            }
            return ret;
        }
    
        return 0;
    }
    
    static int test_close(struct inode *inode, struct file *file)
    {
        int i, irq;
    
        for(i = 0; i < ARRAY_SIZE(btn); i++)
        {
            irq = gpio_to_irq(btn[i].gpio);
            free_irq(irq, &btn[i]);
        }
    
        return 0;
    }
    
    static ssize_t test_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
    {
        int ret;
    
        if(count > ARRAY_SIZE(key_state))
            count = ARRAY_SIZE(key_state);
    
        while(!ev_key)
        {
            if(file->f_flags & O_NONBLOCK)
                return -EAGAIN;
    
            if(wait_event_interruptible(wq, ev_key))
                return -ERESTARTSYS;
        }
    
        ret = copy_to_user(buf, key_state, count);
        if(ret)
            return -EFAULT;
    
        memset(key_state, 0, sizeof(key_state));
        ev_key = 0;
    
        return count;
    }
    
    static struct file_operations fops = {
        .owner      = THIS_MODULE,
        .open       = test_open,
        .release    = test_close,
        .read       = test_read,
    };
    
    int major;
    int __init test_init(void)
    {
        int ret;
    
        setup_timer(&timer, timer_main, 11223344);
        ret = register_chrdev(major,
                              DEV_NAME, &fops);
        if(ret > 0)
        {
            major = ret;
            printk("major = %d\n", major);
            ret = 0;
        }
    
        return ret;
    }
    
    void __exit test_exit(void)
    {
        del_timer_sync(&timer);
        unregister_chrdev(major, DEV_NAME);
    }
    
    module_init(test_init);
    module_exit(test_exit);
    
    MODULE_LICENSE("GPL");

八. 测试按键驱动:
    #include <stdio.h>
    #include <string.h>
    #include <stdlib.h>
    #include <unistd.h>
    #include <fcntl.h>
    
    int main(int argc, char **argv)
    {
        int fd, i, ret;
        char buf[4];
    
        fd = open(argv[1], O_RDWR);
        if(-1 == fd)
        {
            perror("open");
            exit(1);
        }
    
        while(1)
        {
            ret = read(fd, buf, sizeof(buf));
            if(4 != ret)
                continue;
    
            for(i = 0; i < sizeof(buf); i++)
            {
                if(buf[i] == 1)
                    printf("key%d down.\n", i + 1);
            }
        }
    
        close(fd);
        return 0;
    }