最全Linux驱动开发八股文（十六）

你好，我是拉依达。

这是我的Linux驱动开发八股文详细解析系列。

本系列最开始是我在csdn上更新的文章，目前已经是csdn搜索“linux驱动”综合推荐第一名，累计阅读次数4w次。

全文总字数近8w字，是目前全网最全面，最清晰的入门linux驱动学习资料。

现重新对内容进行整理，希望可以帮助到更多学习嵌入式的同学。

15.4 platform 总线框架例程

一、应用层

int main(int argc, char *argv[])
{
    int fd, retvalue;
    char *filename;
    unsigned char databuf[1];
    unsigned char readbuf[1];

    if(argc != 3)
    {
        printf("Error Usage!\r\n");
        return -1;
    }

    filename = argv[1];

    fd = open(filename, O_RDWR);
    if(fd < 0)
    {
        printf("file %s open failed!\r\n", argv[1]);
        return -1;
    }
    databuf[0] = atoi(argv[2]); /* 要执行的操作：打开或关闭 */
    if(databuf[0] ==  2)
    {
         retvalue = read(fd,readbuf,sizeof(readbuf));
        if(retvalue < 0)
        {
            printf("read file %s failed!\r\n",filename);
        }
        else
        {
            printf("read date: %x\r\n",readbuf[0]);
        }
    }else
    {
         /* 向/dev/led 文件写入数据 */
        retvalue = write(fd, databuf, sizeof(databuf));
        if(retvalue < 0)
        {
            printf("LED Control Failed!\r\n");
            close(fd);
            return -1;
        }
    }
   
    retvalue = close(fd);
    if(retvalue < 0)
    {
        printf("file %s close failed!\r\n", argv[1]);
        return -1;
    }
    return 0;
}   

二、驱动层（无设备树）

device.c

/* 
 * 寄存器地址定义
 */
#define CCM_CCGR1_BASE				(0X020C406C)	
#define SW_MUX_GPIO1_IO03_BASE		(0X020E0068)
#define SW_PAD_GPIO1_IO03_BASE		(0X020E02F4)
#define GPIO1_DR_BASE				(0X0209C000)
#define GPIO1_GDIR_BASE				(0X0209C004)
#define REGISTER_LENGTH				4
/*  
 * 设备资源信息，也就是LED0所使用的所有寄存器
 */
static struct resource led_resources[] = {
	[0] = {
		.start 	= CCM_CCGR1_BASE,
		.end 	= (CCM_CCGR1_BASE + REGISTER_LENGTH - 1),
		.flags 	= IORESOURCE_MEM,
	},	
	[1] = {
		.start	= SW_MUX_GPIO1_IO03_BASE,
		.end	= (SW_MUX_GPIO1_IO03_BASE + REGISTER_LENGTH - 1),
		.flags	= IORESOURCE_MEM,
	},
	[2] = {
		.start	= SW_PAD_GPIO1_IO03_BASE,
		.end	= (SW_PAD_GPIO1_IO03_BASE + REGISTER_LENGTH - 1),
		.flags	= IORESOURCE_MEM,
	},
	[3] = {
		.start	= GPIO1_DR_BASE,
		.end	= (GPIO1_DR_BASE + REGISTER_LENGTH - 1),
		.flags	= IORESOURCE_MEM,
	},
	[4] = {
		.start	= GPIO1_GDIR_BASE,
		.end	= (GPIO1_GDIR_BASE + REGISTER_LENGTH - 1),
		.flags	= IORESOURCE_MEM,
	},
};
/*
 * platform设备结构体 
 */
static struct platform_device leddevice = {
	.name = "imx6ul-led",
	.id = -1,
	.dev = {
		.release = &led_release,
	},
	.num_resources = ARRAY_SIZE(led_resources),
	.resource = led_resources,
};
static int __init leddevice_init(void)
{
	return platform_device_register(&leddevice);
}
static void __exit leddevice_exit(void)
{
	platform_device_unregister(&leddevice);
}
module_init(leddevice_init);
module_exit(leddevice_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("songwei");

driver.c

#define LEDDEV_CNT		1			/* 设备号长度 	*/
#define LEDDEV_NAME		"platled"	/* 设备名字 	*/
#define LEDOFF 			0
#define LEDON 			1
/* 寄存器名 */
static void __iomem *IMX6U_CCM_CCGR1;
static void __iomem *SW_MUX_GPIO1_IO03;
static void __iomem *SW_PAD_GPIO1_IO03;
static void __iomem *GPIO1_DR;
static void __iomem *GPIO1_GDIR;
/* leddev设备结构体 */
struct leddev_dev{
	......	
};
struct leddev_dev leddev; 	/* led设备 */

static struct file_operations led_fops = {
	.owner = THIS_MODULE,
    .read = led_read,
	.open = led_open,
	.write = led_write,
};

/*
 * @description		: flatform驱动的probe函数，当驱动与
 * 					  设备匹配以后此函数就会执行
 * @param - dev 	: platform设备
 * @return 			: 0，成功;其他负值,失败
 */
static int led_probe(struct platform_device *dev)
{	
	int i = 0;
	int ressize[5];
	u32 val = 0;
	struct resource *ledsource[5];

	printk("led driver and device has matched!\r\n");
	/* 1、获取资源 */
	for (i = 0; i < 5; i++) {
		ledsource[i] = platform_get_resource(dev, IORESOURCE_MEM, i); /* 依次MEM类型资源 */
		if (!ledsource[i]) {
			dev_err(&dev->dev, "No MEM resource for always on\n");
			return -ENXIO;
		}
		ressize[i] = resource_size(ledsource[i]);	
	}	
	......
}
static int led_remove(struct platform_device *dev)
{
	iounmap(IMX6U_CCM_CCGR1);
	iounmap(SW_MUX_GPIO1_IO03);
	iounmap(SW_PAD_GPIO1_IO03);
	iounmap(GPIO1_DR);
	iounmap(GPIO1_GDIR);
	......
}
/* platform驱动结构体 */
static struct platform_driver led_driver = {
	.driver		= {
		.name	= "imx6ul-led",			/* 驱动名字，用于和设备匹配 */
	},
	.probe		= led_probe,
	.remove		= led_remove,
};
static int __init leddriver_init(void)
{
	return platform_driver_register(&led_driver);
}
static void __exit leddriver_exit(void)
{
	platform_driver_unregister(&led_driver);
}
module_init(leddriver_init);
module_exit(leddriver_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("songwei");

二、驱动层（有设备树）

driver.c

#define LEDDEV_CNT		1			/* 设备号长度 	*/
#define LEDDEV_NAME		"dts_platled"	/* 设备名字 	*/
#define LEDOFF 			0
#define LEDON 			1

/* leddev设备结构体 */
struct leddev_dev{
	......
    struct device_node *node;	/* LED设备节点 */
	int led0;					/* LED灯GPIO标号 */	
};

struct leddev_dev leddev; 	/* led设备 */

static struct file_operations led_fops = {
	.owner = THIS_MODULE,
    .read = led_read,
	.open = led_open,
	.write = led_write,
};
/*
 * @description		: flatform驱动的probe函数，当驱动与
 * 					  设备匹配以后此函数就会执行
 * @param - dev 	: platform设备
 * @return 			: 0，成功;其他负值,失败
 */
static int led_probe(struct platform_device *dev)
{	
	......
    /* 6、初始化IO */	
	leddev.node = of_find_node_by_path("/gpioled");
	if (leddev.node == NULL){
		printk("gpioled node nost find!\r\n");
		return -EINVAL;
	} 
	leddev.led0 = of_get_named_gpio(leddev.node, "led-gpio", 0);
	if (leddev.led0 < 0) {
		printk("can't get led-gpio\r\n");
		return -EINVAL;
	}
	gpio_request(leddev.led0, "led0");
	gpio_direction_output(leddev.led0, 1); /* led0 IO设置为输出，默认高电平	*/
	return 0;
}

/*
 * @description		: platform驱动的remove函数，移除platform驱动的时候此函数会执行
 * @param - dev 	: platform设备
 * @return 			: 0，成功;其他负值,失败
 */
static int led_remove(struct platform_device *dev)
{
    gpio_set_value(leddev.led0, 1); 	/* 卸载驱动的时候关闭LED */
	gpio_free(leddev.led0);				/* 释放IO 			*/

	......
}

/* 匹配列表 */
static const struct of_device_id led_of_match[] = {
	{ .compatible = "songwei-gpioled" },
	{ /* Sentinel */ }
};

/* platform驱动结构体 */
static struct platform_driver led_driver = {
	.driver		= {
		.name	= "imx6ul-led",			/* 驱动名字，用于和设备匹配 */
        .of_match_table	= led_of_match, /* 设备树匹配表 		 */
	},
	.probe		= led_probe,
	.remove		= led_remove,
};

static int __init leddriver_init(void)
{
	return platform_driver_register(&led_driver);
}

static void __exit leddriver_exit(void)
{
	platform_driver_unregister(&led_driver);
}
module_init(leddriver_init);
module_exit(leddriver_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("songwei");