字符设备驱动之led灯的控制实验

最新推荐文章于 2024-04-09 22:54:38 发布

原创最新推荐文章于 2024-04-09 22:54:38 发布 · 1.2k 阅读

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#linux #内核 #驱动

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本文深入探讨了Linux设备驱动开发的全过程，从初始化到退出，包括注册设备、内存分配、设备节点创建、文件操作集关联及设备添加到系统中等关键步骤。详细展示了如何通过宏定义和函数实现GPIO配置、打开和关闭LED灯的功能。

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/poll.h>
#include <linux/irq.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/interrupt.h>
#include <asm/uaccess.h>
#include <linux/platform_device.h>
#include <linux/cdev.h>
#include <linux/miscdevice.h>
#include <linux/slab.h>
#define DEVICE_NAME "leds"
#define  GPIOCFG1  (*(volatile unsigned long*) 0xbfd010C4) 
#define  GPIOOE1   (*(volatile unsigned long*)0xbfd010D4)   
#define  GPIOOUT1  (*(volatile unsigned long*)0xbfd010F4)  
static struct led_dev {
	dev_t devno;
	struct cdev cdev;	
};

struct led_dev *leds = NULL;

static int leds_open(struct inode *inode, struct file *file)
{
    printk(KERN_WARNING "open led linght\n");
    GPIOCFG1 |= 0x000000C0;
    GPIOOE1 &= ~(0x000000C0);
    GPIOOUT1 &= ~(0x000000C0);   
    return 0;
}

/*static int leds_close(struct inode *inode, struct file *file)
{
    
    printk(KERN_WARNING "close\n");
    return 0;
}*/

static int leds_ioctl(struct inode *inode, struct file *file,
        unsigned int cmd, unsigned long arg)
{
    return 0;
}

static struct file_operations dev_fops = {
    .owner	= THIS_MODULE,
    .open	= leds_open,
    .unlocked_ioctl	= leds_ioctl,
   /* .release	= leds_close,*/
};

static int __init dev_init(void)/*驱动的初始化*/
{
    int ret;
	dev_t devno=MKDEV(252,0);

    ret = register_chrdev_region(devno,1,"leds");/*静态注册设备号*/
	if(ret < 0){
		printk(KERN_WARNING "leds:can't get major.\n");
		goto fail;
	}

	leds = kmalloc(sizeof(struct led_dev), GFP_KERNEL);	/*设备节点分配内存空间*/
	if(!leds){
		ret = -ENOMEM;
		goto fail;
	}
	memset(leds, 0, sizeof(struct led_dev));
	leds->devno = devno;

	cdev_init(&leds->cdev, &dev_fops);/*关联操作集*/
	leds->cdev.owner = THIS_MODULE;
	ret = cdev_add(&leds->cdev, devno, 1);/*将设备加入到系统中*/
	if(ret){
		printk(KERN_NOTICE "Error %d.\n", ret);
		goto fail;
	}
	
    printk ("led driver initialized.\n");
    return 0;

fail:
	if(devno != 0){
		unregister_chrdev_region(&devno, 1);
	}
	if(leds){
		kfree(leds);
	}
	return ret;
}
static void __exit dev_exit(void)/*释放设备节点*/
{
	dev_t devno = leds->devno;

	cdev_del(&leds->cdev);
	if(leds){
		kfree(leds);
	}
	unregister_chrdev_region(devno, 1);
}

module_init(dev_init);
module_exit(dev_exit);
MODULE_LICENSE("GPL");