字符设备驱动笔记——异步通知（八）
一、信号处理函数的要点：
1.注册一个信号处理函数
2.发信号，谁发
3.发给谁
4.怎么发
#include <stdio.h> #include <signal.h> void my_signal_fun(int signum) { static int cnt = 0; printf("signal = %d, %d times\n", signum, ++cnt); } int main(int argc, char **argv) { signal(SIGUSR1, my_signal_fun); while (1) { sleep(1000); } return 0; }
二、执行：
//执行 kill -USR1 833 //或者 //kill -10 833 //kill -9 833
三、驱动程序
目标：
按下按键时，驱动程序通知应用程序
步骤：
1.应用程序中注册信号处理函数
2.驱动程序发送信号
3.信号发给应用程序，应用程序告诉驱动程序PID
4.驱动程序：kill_fasync
实现：
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：
应用程序调用fcntl()函数告诉驱动程序，发给谁
fcntl(fd, F_SETOWN, getpid()); // 告诉内核，发给谁
//修改flag
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
四、fifth_drv.c
#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); 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，推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");
五、fifthdrvtest.c
#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); fd = open("/dev/buttons", O_RDWR); if (fd < 0) { printf("can't open!\n"); } fcntl(fd, F_SETOWN, getpid()); Oflags = fcntl(fd, F_GETFL); fcntl(fd, F_SETFL, Oflags | FASYNC); while (1) { sleep(1000); } return 0; }
六、Makefile
KERN_DIR = /work/system/linux-2.6.22.6 all: make -C $(KERN_DIR) M=`pwd` modules clean: make -C $(KERN_DIR) M=`pwd` modules clean rm -rf modules.order obj-m += fifth_drv.o
