在按键驱动中增加异步通知的例子

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我是靠谱客的博主跳跃狗，最近开发中收集的这篇文章主要介绍在按键驱动中增加异步通知的例子，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

//misc_key_async.c

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/poll.h>
7 #include <linux/irq.h> // #define S3C_EINT(x) ((x) + S3C_IRQ_EINT_BASE)   #define IRQ_EINT(x) S3C_EINT(x)
8 #include<linux/mm.h>
9 #include<linux/sched.h>
10 #include<asm/system.h>
11 #include <asm/irq.h>
12 #include <asm/io.h>
13 #include <linux/interrupt.h>
14 #include <asm/uaccess.h>
15 #include <mach/hardware.h>
16 #include <linux/platform_device.h>
17 #include <linux/cdev.h>
18 #include <linux/miscdevice.h>
19 #include <mach/map.h>
20 #include <mach/regs-clock.h>
21 #include <mach/regs-gpio.h>
22 #include <plat/gpio-cfg.h>
23 #include <mach/gpio-bank-n.h>
24 #include <mach/gpio-bank-l.h> //#define S3C64XX_GPLDAT (S3C64XX_GPL_BASE + 0x08)
25
26 #define DEVICE_NAME "button_by_hui"
27
28 struct fasync_struct *async_queue; /*异步结构体指针，用于读*/
29
30 struct button_irq_desc{
31     int irq;
32     int number;
33     char *name;
34 };
35
36 static struct button_irq_desc button_irqs[] = {
37     {IRQ_EINT(0), 0, "KEY0"},
38     {IRQ_EINT(1), 1, "KEY1"},
39     {IRQ_EINT(2), 2, "KEY2"},
40     {IRQ_EINT(3), 3, "KEY3"},
41     {IRQ_EINT(4), 4, "KEY4"},
42     {IRQ_EINT(5), 5, "KEY5"},
43     {IRQ_EINT(19), 6, "KEY6"},
44     {IRQ_EINT(20), 7, "KEY7"},
45 };
46 static volatile char key_values[] = {'0', '0', '0', '0', '0', '0', '0', '0'};
47
48 static DECLARE_WAIT_QUEUE_HEAD(button_waitq); /*定义一个新的等待队列的头*/
49 static volatile int ev_press = 0;             /*判断是否有按键按下的标志位*/
50
51 static irqreturn_t buttons_interrupt(int irq, void *dev_id) /*中断处理函数*/
52 {                                                   /*(void *)&button_irqs[i]申请中断时传进来的参数*/
53     struct button_irq_desc *button_irqs = (struct button_irq_desc *)dev_id;
54     int down;
55     int number;
56     unsigned tmp;
57     udelay(0);
58     number = button_irqs->number;
59     switch(number) {
60         case 0: case 1: case 2: case 3: case 4: case 5:
61             tmp = readl(S3C64XX_GPNDAT); //
62             down = !(tmp & (1<<number));
63             break;
64         case 6: case 7:
65             tmp = readl(S3C64XX_GPLDAT); /*（返回）从映射的I/O空间读取32位4字节的数值 */
66             down = !(tmp & (1 << (number + 5)));
67             break;
68         default:
69             down = 0;
70     }
71     if (down != (key_values[number] & 1)) {
72         key_values[number] = '0' + down;
73         ev_press = 1;
74         wake_up_interruptible(&button_waitq);   /*唤醒阻塞（睡眠）的读等待队列*/
75
76         /*产生异步读信号通知相关进程把要发送的SIGIO 信号发送出去*/
77         if(async_queue){
78                kill_fasync(&async_queue, SIGIO, POLL_IN);
79          #ifdef DEBUG
80                printk("<0>%s kill SIGIOn", __func__);
81          #endif
82         }
83     }
84     /* //means that we did have a valid interrupt and handled it
85      * #define IRQ_RETVAL(x) ((x) != IRQ_NONE )   //这个宏只是返回0或非0
86      */
87     return IRQ_RETVAL(IRQ_HANDLED);
88 }
89
90 static int s3c64xx_buttons_open(struct inode *inode, struct file *file)
91 {
92     int i;
93     int err = 0;
94     for (i = 0; i < sizeof(button_irqs)/sizeof(button_irqs[0]); i++) {
95         if (button_irqs[i].irq < 0) {
96             continue;
97         }                 /*中断号            处理函数           双延触发*/
98         err = request_irq(button_irqs[i].irq, buttons_interrupt, IRQ_TYPE_EDGE_BOTH,    /*申请中断*/
99                 button_irqs[i].name, (void *)&button_irqs[i]);
100                 /*在proc/interrupts中显示中断拥有者   void *dev_id*/
101         if (err)
102             break;
103     }
104     if (err) { /*出错处理把之前分配的中断释放掉*/
105         i--;
106         for (; i >= 0; i--) {
107             if (button_irqs[i].irq < 0){
108                 continue;
109             }
110             disable_irq(button_irqs[i].irq);
111             free_irq(button_irqs[i].irq, (void *)&button_irqs[i]);
112         }
113         return -EBUSY;
114     }
115     ev_press = 1;
116     return 0;
117 }
118
119 static int s3c64xx_buttons_close(struct inode *inode, struct file *file)
120 {
121     int i;
122     for (i = 0; i < sizeof(button_irqs)/sizeof(button_irqs[0]); i++) {
123         if (button_irqs[i].irq < 0) {
124             continue;
125         }
126         free_irq(button_irqs[i].irq, (void *)&button_irqs[i]);
127     }
128     return 0;
129 }
130
131 static int s3c64xx_buttons_read(struct file *filp, char __user *buff, size_t count, loff_t *offp)
132 {
133     unsigned long err;
134     if (!ev_press) {
135         if (filp->f_flags & O_NONBLOCK)
136             return -EAGAIN;
137         else{
138             /*这个宏：使调用进程在等待队上睡眠，一直到修改了给定条件为止*/
139             wait_event_interruptible(button_waitq, ev_press); /*直到ev_press 为 1*/
140         }
141     }
142     ev_press = 0;
143     err = copy_to_user((void *)buff, (const void *)(&key_values), min(sizeof(key_values), count));
144     return err ? -EFAULT : min(sizeof(key_values), count);
145 }
146
147 static unsigned int s3c64xx_buttons_poll( struct file *file, struct poll_table_struct *wait)
148 {
149     unsigned int mask = 0;
150     poll_wait(file, &button_waitq, wait);
151     if (ev_press){
152         mask |= POLLIN | POLLRDNORM; //有键按下标示数据可以读取
153     }
154     ev_press = 0;
155     return mask;
156 }
157
158 /*增加支持异步通知的函数在release 函数中调用 */
159 static int misc_key_fasync(int fd, struct file *filp, int mode)
160 {
161
162     /*将文件从异步通知列表（相关进程列表）中删除*/
163      return fasync_helper(fd, filp, mode, &async_queue);
164 }
165
166 /*文件释放函数*/
167 int misc_key_release(struct inode *inode, struct file *filp)
168 {
169     /*将文件从异步通知列表中删除*/
170     misc_key_fasync(-1, filp, 0);
171     return 0;
172 }
173
174 static struct file_operations dev_fops = {
175     .owner   = THIS_MODULE,
176     .open    = s3c64xx_buttons_open,
177     .release = s3c64xx_buttons_close,
178     .read    = s3c64xx_buttons_read,
179     .poll    = s3c64xx_buttons_poll,
180     .fasync = misc_key_fasync, /*不要忘了在这里也要加上与内核联系的接口*/
181     .release = misc_key_release,
182 };
183
184 static struct miscdevice misc = { /*杂项字符设备结构体*/
185     .minor = MISC_DYNAMIC_MINOR, /*次设备号表示自动分配*/
186     .name = DEVICE_NAME,         /*设备名*/
187     .fops = &dev_fops,           /*设备操作*/
188 };
189
190 static int __init dev_init(void)
191 {
192     int ret;
193     ret = misc_register(&misc);             /*注册一个混杂设备在加载模块时会自动创建设备文件，为主设备号为10的字符设备*/
194     printk(DEVICE_NAME"tinitializedn");   /*无需mknod指令创建设备文件。因为misc_register()会调用class_device_create()或者device_create()*/
195     return ret;
196 }
197
198
199
200 static void __exit dev_exit(void)
201 {
202
203     misc_deregister(&misc);                 /*注销混杂设备自动删除设备文件*/
204 }
205
206 module_init(dev_init);
207 module_exit(dev_exit);
208 MODULE_LICENSE("GPL");
209 MODULE_AUTHOR("FriendlyARM Inc.");
210

  //misc_key_async.c
  1 #include<stdio.h>
  2 #include<stdlib.h>
  3 #include<unistd.h>
  4 #include<fcntl.h>
  5 #include<signal.h>
  6 #include<sys/stat.h>
  7 
  8 //#define DEBUG
  9 
 10 #ifdef DEBUG
 11 #define MAX_LEN 100
 12 #endif
 13 
 14 /*接受到异步读信号后的动作*/
 15 void input_handler(int signum)
 16 {
 17 #ifdef DEBUG
 18     char data[MAX_LEN];
 19     int len;
 20     /*读取并输出SIDIN_FILENO 上的输入*/
 21     len = read(fd, &data, MAX_LEN);
 22     data[len] = '';
 23     printf("input available:%s", data);
 24 
 25 #endif
 26     printf("receive a signal from globalfifo, signalnum:%dn",signum);
 27 }
 28 
 29 int main(void)
 30 {
 31     int fd,oflags;
 32     fd = open("/dev/button_by_hui", O_RDWR, S_IRUSR | S_IWUSR);
 33     if(fd != -1){
 34         /*启动信号驱动机制*/         /*设置信号处理函数*/
 35         signal(SIGIO, input_handler);/*让input_handler()函数处理SIGIO信号*/
 36         fcntl(fd, F_SETOWN, getpid()); /*通过F_SETOWN IO控制命令设置设备文件拥有者为本进程*/
 37         oflags = fcntl(fd, F_GETFL);/*F_GETFL 命令 取得fd设备文件状态标志*/
 38         fcntl(fd, F_SETFL, oflags | FASYNC); /*F_SETFL 命令设置设备文件支持FASYNC（异步通知模式）*/
 39         while(1){
 40             sleep(100);
 41         }
 42     }else{
 43         printf("device open failuren");
 44     }
 45 }