led_drv

本文主要是介绍led_drv，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/slab.h>

#include <asm/uaccess.h>
#include <asm/io.h>

//设计一个类型，描述一个设备的信息
struct led_desc{
unsigned int dev_major; //设备号
struct class *cls;
struct device *dev; //创建设备文件
void *reg_virt_base; //表示是寄存器地址到基准值
int pin_NO;
};

//物理地址
#define GPX2_CON 0x11000C40
#define GPX2_SIZE 8
#define PIN 7

struct led_desc *led_dev;//表示一个全局的设备对象

static int kernel_val = 555;

// read(fd, buf, size);
ssize_t led_drv_read(struct file *filp, char __user *buf, size_t count, loff_t *fpos)
{
printk("-------%s-------\n", __FUNCTION__);

int ret;

ret = copy_to_user(buf, &kernel_val, count);
if(ret > 0)
{
printk("copy_to_user error\n");
return -EFAULT;
}


return 0;

}
ssize_t led_drv_write(struct file *filp, const char __user *buf, size_t count, loff_t *fpos)
{
//printk("-------%s-------\n", __FUNCTION__);

int ret;
int value;

ret = copy_from_user(&value, buf, count);
if(ret > 0)
{
printk("copy_to_user error\n");
return -EFAULT;
}

if(value){
writel( readl(led_dev->reg_virt_base + 4) | (1<<PIN), led_dev->reg_virt_base + 4 );

}else{
writel( readl(led_dev->reg_virt_base + 4) & ~(1<<7), led_dev->reg_virt_base + 4 );
}

return 0;

}
int led_drv_open(struct inode *inode, struct file *filp)
{
printk("-------%s-------\n", __FUNCTION__);

return 0;
}

int led_drv_close(struct inode *inode, struct file *filp)
{
printk("-------%s-------\n", __FUNCTION__);
return 0;

}

const struct file_operations my_fops = {
.open = led_drv_open,
.read = led_drv_read,
.write = led_drv_write,
.release = led_drv_close,
};

static int __init led_dev_init(device *dev)
{
int ret;

// 0， 实例化全局的设备对象--分配空间
led_dev = kmalloc(sizeof(struct led_desc), GFP_KERNEL);
if(led_dev == NULL)
{
printk(KERN_ERR "malloc error\n");
return -ENOMEM;
}

// 1, 一般都是申请设备号资源
// 申请设备号
led_dev->dev_major = register_chrdev(0, "led_dev_test", &my_fops);
if(led_dev->dev_major < 0)
{
printk(KERN_ERR "register_chrdev error\n");
ret = -ENODEV;
goto err_0;
}

// 2，创建设备文件
led_dev->cls = class_create(THIS_MODULE, "led_cls");
if(IS_ERR(led_dev->cls))
{
printk(KERN_ERR "class_create error\n");
ret = PTR_ERR(led_dev->cls); //将指针出错的具体原因转换成一个出错码
goto err_1;
}

// /dev/led0
led_dev->dev = device_create(led_dev->cls, NULL,
MKDEV(led_dev->dev_major, 0), NULL, "led%d", 0);
if(IS_ERR(led_dev->dev))
{
printk(KERN_ERR "device_create error\n");
ret = PTR_ERR(led_dev->dev); //将指针出错的具体原因转换成一个出错码
goto err_2;
}

// 3,硬件初始化
// 对地址进行映射
led_dev->reg_virt_base = ioremap(GPX2_CON, GPX2_SIZE);
if(led_dev->reg_virt_base == NULL)
{

printk(KERN_ERR "ioremap error\n");
ret = -ENOMEM;
goto err_3;
}

// gpio的输出功能的配置
u32 value = readl(led_dev->reg_virt_base);
value &= ~(0xf<<28);
value |= (0x1<<28);
writel(value, led_dev->reg_virt_base);

return 0;

err_3:
device_destroy(led_dev->cls, MKDEV(led_dev->dev_major, 0));

err_2:
class_destroy(led_dev->cls);

err_1:
unregister_chrdev(led_dev->dev_major, "led_dev_test");

err_0:
kfree(led_dev);
return ret;

}

static void __exit led_dev_exit(void)
{
//一般都是释放资源
iounmap(led_dev->reg_virt_base);
device_destroy(led_dev->cls, MKDEV(led_dev->dev_major, 0));
class_destroy(led_dev->cls);
unregister_chrdev(led_dev->dev_major, "led_dev_test");
kfree(led_dev);

}
module_init(led_dev_init);
module_exit(led_dev_exit);
MODULE_LICENSE("GPL");

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