异步通知
前面三种检测按键的方式:查询(极度耗资源)、中断(读时会休眠,read(...)在没有检测到按键时,不会返回)、poll(在中断的基础上给定一个超时时间,时间到了,即使没有按键按下也会返回)。这三种方法都有一个共同点就是都需要应用程序主动去读。
异步通知可以在驱动程序里面检测,能过信号触发应用程序。
进程间发信号:
1,先注册一个信号处理函数;
2,谁发;
3,发给谁;
4,怎么发。
目标:按键按下时,驱动程序通知应用程序。
1,应用程序里需要注册信号处理函数
2,谁发,驱动程序发
3,发给谁,应用程序 (应用程序要告诉内核他的PID号)
4,怎么发,调用kill_fasync
- #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 = 0;
- 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[4] = {
- {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 = 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); // 发送信号(发生中断后会通过kill_fasync发送信号到应用程序 SIGIO要发送的信号,POLL_IN表示有信号等待读取。
-
- 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[0]);
- request_irq(IRQ_EINT2, buttons_irq, IRQT_BOTHEDGE, "S3", &pins_desc[1]);
- request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "S4", &pins_desc[2]);
- request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "S5", &pins_desc[3]);
- return 0;
- }
- ssize_t fifth_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
- {
- if (size != 1)
- 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, 1);
- ev_press = 0;
-
- return 1;
- }
- int fifth_drv_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]);
- return 0;
- }
- static unsigned fifth_drv_poll(struct file *file, poll_table *wait)
- {
- 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 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,指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(0, "fifth_drv", &sencod_drv_fops);
- fifthdrv_class = class_create(THIS_MODULE, "fifth_drv");
- fifthdrv_class_dev = class_device_create(fifthdrv_class, NULL, MKDEV(major, 0), NULL, "buttons"); /* /dev/buttons */
- gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);
- gpfdat = gpfcon + 1;
- gpgcon = (volatile unsigned long *)ioremap(0x56000060, 16);
- gpgdat = gpgcon + 1;
- return 0;
- }
- 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 0;
- }
- module_init(fifth_drv_init);
- module_exit(fifth_drv_exit);
- MODULE_LICENSE("GPL");
为了使设备支持异步通知机制,驱动程序中涉及以下3项工作:
1. 支持F_SETOWN命令,能在这个控制命令处理中设置filp->f_owner为对应进程ID。
不过此项工作已由内核完成,设备驱动无须处理。
2. 支持F_SETFL命令的处理,每当FASYNC标志改变时,驱动程序中的fasync()函数将得以执行。
驱动中应该实现fasync()函数。
3. 在设备资源可获得时,调用kill_fasync()函数激发相应的信号
应用程序:
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,最终会调用到驱动的faync > fasync_helper:初始化/释放fasync_struct
- #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, 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); // 接收驱动程序中kill_fasync()传来的信号,然后调用my_signal_fun()函数。
-
- fd = open("/dev/buttons", O_RDWR);
- if (fd < 0)
- {
- printf("can't open!\n");
- }
- fcntl(fd, F_SETOWN, getpid()); // 获取进程PID
-
- Oflags = fcntl(fd, F_GETFL);
-
- fcntl(fd, F_SETFL, Oflags | FASYNC); // 异步通知
- while (1)
- {
- sleep(1000);
- }
-
- return 0;
- }
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