imx6q内核之信号量

本文主要是介绍imx6q内核之信号量，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

驱动代码

/*************************************************************************> File Name: led_drv.c> Author: XXDK> Email: v.manstein@qq.com > Created Time: Sat 18 Mar 2017 06:27:26 AM PDT************************************************************************/#include<linux/init.h>
#include<linux/module.h>
#include<linux/fs.h>
#include<linux/cdev.h>
#include<linux/device.h>
#include<linux/slab.h>
#include<asm/gpio.h>
#include<mach/iomux-mx6q.h>#define SABRESD_GPIO_LED4	IMX_GPIO_NR(3, 21)struct led{char name[10];int gpio;int data;int open_cnt;struct semaphore sema;dev_t led_dev_id;struct cdev led_cdev;struct class* led_cls;struct file_operations led_fops;
}*sabre_led = NULL;static int led_open(struct inode* inodp, struct file* filp)
{// 获取信息量, 正常获取立刻返回，如果没有获取信息量，进程// 在此进入等待队列休眠，唤醒有两种方式：// 1. 正常获取信号量，函数返回0// 2. 收到信号引起的唤醒，返回非0if(down_interruptible(&sabre_led->sema)) {printk("wake up by signal\n");return -EINTR;}printk("opening sabre led......\n");gpio_set_value(sabre_led->gpio, 1);return 0;
}static int led_close(struct inode* inodp, struct file* filp)
{printk("closing sabre led device\n");up(&sabre_led->sema); // 唤醒等待队列的休眠进程，释放信号量gpio_set_value(sabre_led->gpio, 0);return 0;
}static int led_init(void)
{sabre_led = (struct led*)kmalloc(sizeof(struct led), GFP_KERNEL);if(NULL == sabre_led) {printk("kmalloc error\n");return -1;}sabre_led->led_fops.owner = THIS_MODULE,sabre_led->led_fops.open = led_open,sabre_led->led_fops.release = led_close;sabre_led->gpio = SABRESD_GPIO_LED4;strcpy(sabre_led->name, "led");gpio_request(sabre_led->gpio, sabre_led->name);gpio_direction_output(sabre_led->gpio, 0);// 1. 申请设备号alloc_chrdev_region(&sabre_led->led_dev_id, 0, 1, "leds");// 2. 初始化字符设备对象cdev_init(&sabre_led->led_cdev, &sabre_led->led_fops);// 3. 添加字符设备对象到内核cdev_add(&sabre_led->led_cdev, sabre_led->led_dev_id, 1);// 4. 自动创建设备文件sabre_led->led_cls = class_create(THIS_MODULE, "xxdk");device_create(sabre_led->led_cls, NULL, sabre_led->led_dev_id, NULL, "sabre_led");// 初始化信号量为互斥信号量sema_init(&sabre_led->sema, 1);	return 0;
}static void led_exit(void)
{gpio_set_value(sabre_led->gpio, 0);gpio_free(sabre_led->gpio);device_destroy(sabre_led->led_cls, sabre_led->led_dev_id);class_destroy(sabre_led->led_cls);cdev_del(&sabre_led->led_cdev);unregister_chrdev_region(sabre_led->led_dev_id, 1);kfree(sabre_led);sabre_led = NULL;printk("bye bye\n");return;
}module_init(led_init);
module_exit(led_exit);
MODULE_LICENSE("GPL");

测试代码

/*************************************************************************> File Name: led_test.c> Author: XXDK> Email: v.manstein@qq.com > Created Time: Sat 18 Mar 2017 08:24:16 AM PDT************************************************************************/#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<fcntl.h>int main()
{int fd;if((fd = open("/dev/sabre_led", O_RDWR)) < 0) {perror("open sabreled failed");}sleep(20);close(fd);return 0;
}

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