imx6q内核之自旋锁

驱动代码

/*************************************************************************> File Name: led_drv.c> Author: XXDK> Email: [e-mail] > 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_LED4IMX_GPIO_NR(3, 21)struct led{char name[10];int gpio;int data;int open_cnt;spinlock_t splock;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){unsigned long flags;// 获取自旋锁spin_lock_irqsave(&sabre_led->splock, flags);if(--sabre_led->open_cnt != 0) {printk("sabre led already be opened\n");sabre_led->open_cnt++;// 释放自旋锁spin_unlock_irqrestore(&sabre_led->splock, flags);return -EBUSY;}spin_unlock_irqrestore(&sabre_led->splock, flags);printk("opening sabre led......\n");gpio_set_value(sabre_led->gpio, 1);return 0;}static int led_close(struct inode* inodp, struct file* filp){unsigned long flags;spin_lock_irqsave(&sabre_led->splock, flags);sabre_led->open_cnt++;spin_unlock_irqrestore(&sabre_led->splock, flags);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");// 初始化自旋锁sabre_led->open_cnt = 1;spin_lock_init(&sabre_led->splock);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: [e-mail] > 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(100);close(fd);while(1);}