内核和用户空间异步通信

异步通信主要又两种方式：信号和netlink。下面例子主要是讲述驱动通过中断方式异步通知用户程序：

1、驱动

/* 
*
* dsp p6a interrupt
* author: helb
* date: 2018-08-08
* 
*/


#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <linux/interrupt.h>

#define DRIVER_NAME 			"p6a"
#define P6A_IOC_MAGIC 			'A'
#define P6A_IOCDTBSIZE 			_IO(P6A_IOC_MAGIC, 0)
#define P6A_IOCGETDTB 			_IO(P6A_IOC_MAGIC, 1)

#define DSP_P6A_PHYS_ADDR 		0xfb007400
#define IOREMAP_SIZE 			1024

struct irq_dev {
	char *name;
	unsigned int irq;
	void *reg_base;
};

static struct fasync_struct *p6a_async;
struct irq_dev p6airq= {"p6airq", 9};

static int p6a_open(struct inode *inode, struct file *file)
{
	printk("Do nothing\n");
	return 0;
}

static int p6a_release(struct inode *inode, struct file *file)
{
	printk("Do nothing\n");
	return 0;
}

static ssize_t p6a_write(struct file *file, const char __user *data, size_t len, loff_t *ppos)
{
	printk("Do nothing\n");
	return 0;
}

static long p6a_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
	printk("Do nothing\n");
	return 0;
}

static int p6a_fasync(int fd, struct file *filp, int on)
{
	printk("p6a fasync\n");
	return fasync_helper(fd, filp, on, &p6a_async);
}

static irqreturn_t p6a_interrupt(int irq, void *dev)
{
	u32 reg;
	reg = readl(p6airq.reg_base + 0x50);
	reg &= ~(1<<0);
	writel(reg, p6airq.reg_base + 0x50);
	kill_fasync(&p6a_async, SIGIO, POLL_IN);
	return IRQ_HANDLED;
}

/*
 *    Kernel Interfaces
 */

static struct file_operations p6a_fops = {
    .owner        = THIS_MODULE,
    .llseek        = no_llseek,
    .write        = p6a_write,
    .unlocked_ioctl = p6a_unlocked_ioctl,
    .open        = p6a_open,
    .release    = p6a_release,
	.fasync 	= p6a_fasync,
};

static struct miscdevice p6a_miscdev = {
    .minor        = MISC_DYNAMIC_MINOR,
    .name        = DRIVER_NAME,
    .fops        = &p6a_fops,
};

static int __init p6a_init(void)
{
    int ret = 0;

    ret = misc_register(&p6a_miscdev);
    if(ret) {
        printk (KERN_ERR "cannot register miscdev (err=%d)\n", ret);
		return ret;
    }

	p6airq.reg_base = ioremap(DSP_P6A_PHYS_ADDR, IOREMAP_SIZE);
	if(p6airq.reg_base == NULL){
		printk("p6a ioremap:%#x failed\n", DSP_P6A_PHYS_ADDR);
		goto error;
	}
		
	ret = request_irq(p6airq.irq, p6a_interrupt, IRQF_SHARED, p6airq.name, (void *)&p6airq);
	if(ret < 0){
		printk("p6a request_irq failed\n");
		goto error;
	}

	return 0;
error:
    misc_deregister(&p6a_miscdev);
	return -1;
}

static void __exit p6a_exit(void)
{    
	iounmap(p6airq.reg_base);
	free_irq(p6airq.irq, (void *)&p6airq);
    misc_deregister(&p6a_miscdev);
}

module_init(p6a_init);
module_exit(p6a_exit);

MODULE_AUTHOR("Byavs");
MODULE_DESCRIPTION("Byavs p6a irq event Device Driver");
MODULE_LICENSE("GPL");

2、用户测试用例

#include<stdio.h>
#include<unistd.h>
#include<signal.h>
#include<fcntl.h>

#define DEV_NAME 		"/dev/p6a"

void sig_handler(int sig)
{
	if(sig == SIGIO){
		printf("Receive io signal from kernel!\n");
	}
}

int main(void)
{
	int fd;
	
	signal(SIGIO, sig_handler);
	fd = open(DEV_NAME, O_RDWR);
	if(fd < 0){
		printf("open %s failed\n", DEV_NAME);
		return -1;
	}

	fcntl(fd, F_SETOWN, getpid());
	fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) |  FASYNC);
	printf("waiting p6a interrupt\n");
	while(1){
		sleep(1);
	}

	return 0;
}