一步一步学习 Linux 驱动之 platform 机制（tiny210 LED 驱动）

1、概述

在一般情况下，2.6内核中已经初始化并挂载了一条platform总线在sysfs文件系统中。那么我们编写platform模型驱动时，需要完成两个工作：1：实现platform驱动 2：实现platform设备，然而在实现这两个工作的过程中还需要实现其他的很多小工作，在后面介绍。platform模型驱动的实现过程核心架构就很简单，如下所示。

platform驱动模型三个对象：platform总线、platform设备、platform驱动。

platform总线对应的内核结构：struct bus_type-->它包含的最关键的函数：match()

platform设备对应的内核结构：struct platform_device-->注册：platform_device_register(unregiste)

platform驱动对应的内核结构：struct platform_driver-->注册：platform_driver_register(unregiste)

简单介绍下platform驱动的工作过程：设备(或驱动)注册的时候，都会引发总线调用自己的match函数来寻找目前platform总线是否挂载有与该设备(或驱动)名字匹配的驱动（或设备）( http://blog.csdn.net/xy010902100449/article/details/45700523 前面我们讲了platform设备驱动的match自动匹配过程), 如果存在则将双方绑定；如果先注册设备，驱动还没有注册，那么设备在被注册到总线上时，将不会匹配到与自己同名的驱动，然后在驱动注册到总线上时，因为设备已注册，那么总线会立即匹配与绑定这时的同名的设备与驱动，再调用驱动中的probe函数等；如果是驱动先注册，同设备驱动一样先会匹配失败，匹配失败将导致它的probe函数暂不调用，而是要等到设备注册成功并与自己匹配绑定后才会调用。

2、代码

/**
* @Author: ZP1015 
*
* @Copyright:SCUT.
* 
* @Function:Platform device driver for led 
* 
* @Creat:2015-06-10
*
* @Modify:2015-12-22
**/

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#include <linux/device.h>
#include <linux/cdev.h>
#include <linux/platform_device.h>

static void Myled_platform_device_release(struct device * dev)
{
    return ;
}
static struct resource Myled_resource[] = {
    [0] = {
            .start = 0xe0200280,
            .end   = 0xe0200280 + 12,
            .flags = IORESOURCE_MEM
    },
};
static struct platform_device Myledplatform_device_led = {
    .name           = "Myled_platform_device_driver",
    .id             = -1,
    .num_resources  = ARRAY_SIZE(Myled_resource),
    .resource       = Myled_resource,
    .dev            = {
          .release  = Myled_platform_device_release,
    },
};
static int __init Myled_platform_device_init(void)
{
    printk("Myled_platform_device add ok!\n");
	return platform_device_register(&Myledplatform_device_led);
}
static void __exit Myled_platform_device_exit(void)
{
    printk("Myled_platform_device remove ok!\n");
	platform_device_unregister(&Myledplatform_device_led);
}
MODULE_AUTHOR("ZP1015");
MODULE_LICENSE("GPL");
module_init(Myled_platform_device_init);
module_exit(Myled_platform_device_exit);
//////////////////////////////

/*** @Author: ZP1015 ** @Copyright:SCUT.* * @Function:Platform  driver for led * * @Creat:2015-06-10** @Modify:2015-12-22**/#include <linux/init.h>#include <linux/module.h>#include <linux/fs.h>#include <asm/io.h>#include <asm/uaccess.h>#include <linux/device.h>#include <linux/cdev.h>#include <linux/platform_device.h>#define GLOBAL_LED_MAJOR  250static unsigned int global_led_major = GLOBAL_LED_MAJOR; static struct cdev *led_cdev = NULL; static struct class *led_class = NULL;volatile unsigned long *gpbcon = NULL;volatile unsigned long *gpbdat = NULL; volatile unsigned long *gpbup = NULL; static int Myled_open(struct inode * inode,struct file * file){	return 0;}static ssize_t Myled_read(struct file * file,char __user * in,size_t size,loff_t * off){	return 0;}static ssize_t Myled_write(struct file * file,const char __user * in,size_t size,loff_t * off){	return 0;}static void myled_configure(void){		*gpbcon &= ~((0x3<<(0*4)) | (0x3<<(1*4)) | (0x3<<(2*4)) | (0x3<<(3*4)));	*gpbcon |=  ((0x1<<(0*4)) | (0x1<<(1*4)) | (0x1<<(2*4)) | (0x1<<(3*4)));}static void myled_on(void){	*gpbdat &= ~((1<<0) | (1<<1) | (1<<2) | (1<<3));// 点灯}static void myled_off(void){	*gpbdat |= (1 << 0)|(1 << 1)|(1 << 2)|(1 << 3);// 灭灯	}struct file_operations led_fops = {	.owner = THIS_MODULE,	.open  = Myled_open,	.read  = Myled_read,	.write = Myled_write,};static int __devinit Myled_probe(struct platform_device *pdev){	int ret;	int err;	dev_t devno;	struct resource *pIORESOURCE_MEM = NULL;		printk(KERN_ALERT"Myled_probe!\n");		/*1.初始化cdev*/	led_cdev = cdev_alloc();//分配cdev	cdev_init(led_cdev,&led_fops);//初始化cdev	led_cdev->owner = THIS_MODULE;		/*2.获取字符设备号*/	devno = MKDEV(global_led_major,0);//将主设备号和次设备号转换成dev_t类型	if (devno) {		ret = register_chrdev_region(devno,1,"Myled_platfor_driver");//注册一系列设备号	} 	else {		ret = alloc_chrdev_region(&devno,0,1,"Myled_platfor_driver");//未知主设备号注册设备号		global_led_major = MAJOR(devno);	}		if (ret < 0) {		return ret;	}		/*3.注册字符设备*/	err = cdev_add(led_cdev,devno,1);//注册cdev	if (err) {		printk(KERN_NOTICE"Error %d adding led_cdev",err);		return -1;	} else {		printk(KERN_NOTICE"Myled_platfor_driver init ok!\n");		}		/*4.注册platform机制,在/sys/class/下创建类目录*/	led_class = class_create(THIS_MODULE,"Myled_platfor_driver");//自动创建设备节点	device_create(led_class,NULL,devno,NULL,"platfor_driver_for_Myled");	pIORESOURCE_MEM = platform_get_resource(pdev,IORESOURCE_MEM,0);		gpbcon = ioremap(pIORESOURCE_MEM->start,pIORESOURCE_MEM->end - pIORESOURCE_MEM->start);	gpbdat = gpbcon + 1;	gpbup  = gpbcon + 2;		myled_configure();	myled_on();		printk(KERN_NOTICE"platfor_driver_for_Myled init ok!\n");	return 0;}static int __devexit Myled_remove(struct platform_device *pdev){	dev_t devno;	devno = MKDEV(global_led_major,0);//将主设备号和次设备号转换成dev_t类型	printk("Myled_remove!\n");	myled_off();	cdev_del(led_cdev);	iounmap(gpbcon);	unregister_chrdev_region(devno,1);	device_destroy(led_class,devno);	class_destroy(led_class);		return 0;}static struct platform_driver Myled_platform_driver = {	.probe  = Myled_probe,	.remove = __devexit_p(Myled_remove),	.driver = {		.name = "Myled_platform_device_driver",		.owner = THIS_MODULE,	}};static int __init Myled_platform_driver_init(void){    printk("platform_driver_for_Myled init\n");	return platform_driver_register(&Myled_platform_driver);}static void __exit Myled_platform_driver_exit(void){    printk("platform_driver_for_Myled exit\n");	platform_driver_unregister(&Myled_platform_driver);}MODULE_AUTHOR("ZP1015");MODULE_LICENSE("GPL");module_param(global_led_major,int,S_IRUGO);module_init(Myled_platform_driver_init);module_exit(Myled_platform_driver_exit);///////////////////////

3、实现结果

先注册设备，然后注册设备驱动

insmod 一下灯全亮，rmmod 一下等全灭。

4、系统调用方式

/**
* @Author: ZP1015 
*
* @Copyright:SCUT.
* 
* @Function:Platform  driver for led 
* 
* @Creat:2015-06-10
*
* @Modify:2015-12-22
**/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#include <linux/device.h>
#include <linux/cdev.h>
#include <linux/platform_device.h>

#define GLOBAL_LED_MAJOR  250
#define DEVICE_NAME "Myled_platfor_driver"

static unsigned int global_led_major = GLOBAL_LED_MAJOR; 
static struct cdev *led_cdev = NULL; 
static struct class *led_class = NULL;

volatile unsigned long *gpbcon = NULL;
volatile unsigned long *gpbdat = NULL; 
volatile unsigned long *gpbup = NULL; 

static void myled_configure(void)
{	
	*gpbcon &= ~((0x3<<(0*4)) | (0x3<<(1*4)) | (0x3<<(2*4)) | (0x3<<(3*4)));
	*gpbcon |=  ((0x1<<(0*4)) | (0x1<<(1*4)) | (0x1<<(2*4)) | (0x1<<(3*4)));
}

static void myled_on(void)
{
	*gpbdat &= ~((1<<0) | (1<<1) | (1<<2) | (1<<3));// 点灯
}

static void myled_off(void)
{
	*gpbdat |= (1 << 0)|(1 << 1)|(1 << 2)|(1 << 3);// 灭灯	
}

static int Myled_open(struct inode * inode,struct file * file)
{
	myled_configure();

	return 0;
}

static ssize_t Myled_read(struct file * file,char __user * in,size_t size,loff_t * off)
{
	return 0;
}

static ssize_t Myled_write(struct file * file,const char __user * in,size_t size,loff_t * off)
{
	char val[1];

	if(copy_from_user(val, in, size)) {//用户到内核空间
		return -EFAULT;
	}

	printk("[%s,%d]val:%c %d\n",__func__,__LINE__,val[0],val[0]);

	switch(val[0]) {
		case '0':
			myled_on();
			break;
		case '1':
			myled_off();
			break;
	}

	return 0;
}

struct file_operations led_fops = {
	.owner = THIS_MODULE,
	.open  = Myled_open,
	.read  = Myled_read,
	.write = Myled_write,
};
static int __devinit Myled_probe(struct platform_device *pdev)
{
	int ret;
	int err;
	dev_t devno;
	struct resource *pIORESOURCE_MEM = NULL;

	printk(KERN_ALERT"Myled_probe!\n");

	/*1.初始化cdev*/
	led_cdev = cdev_alloc();//分配cdev
	cdev_init(led_cdev,&led_fops);//初始化cdev
	led_cdev->owner = THIS_MODULE;

	/*2.获取字符设备号*/
	devno = MKDEV(global_led_major,0);//将主设备号和次设备号转换成dev_t类型
	if (devno) {
		ret = register_chrdev_region(devno,1,DEVICE_NAME);//注册一系列设备号
	} 
	else {
		ret = alloc_chrdev_region(&devno,0,1,DEVICE_NAME);//未知主设备号注册设备号
		global_led_major = MAJOR(devno);
	}

	if (ret < 0) {
		return ret;
	}

	/*3.注册字符设备*/
	err = cdev_add(led_cdev,devno,1);//注册cdev
	if (err) {
		printk(KERN_NOTICE"Error %d adding led_cdev",err);
		return -1;
	} else {
		printk(KERN_NOTICE"Myled_platfor_driver init ok!\n");	
	}

	/*4.自动创建设备节点,在/sys/class/下创建类目录*/
	led_class = class_create(THIS_MODULE,"myled_class");//自动创建设备节点
	device_create(led_class,NULL,devno,NULL,"myled");

	pIORESOURCE_MEM = platform_get_resource(pdev,IORESOURCE_MEM,0);

	gpbcon = ioremap(pIORESOURCE_MEM->start,pIORESOURCE_MEM->end - pIORESOURCE_MEM->start);
	gpbdat = gpbcon + 1;
	gpbup  = gpbcon + 2;

	printk(KERN_NOTICE"Myled_platfor_driver init ok!\n");

	return 0;
}

static int __devexit Myled_remove(struct platform_device *pdev)
{
	dev_t devno;
	devno = MKDEV(global_led_major,0);//将主设备号和次设备号转换成dev_t类型

	printk("Myled_remove!\n");
	myled_off();

	cdev_del(led_cdev);
	iounmap(gpbcon);
	unregister_chrdev_region(devno,1);
	device_destroy(led_class,devno);
	class_destroy(led_class);

	return 0;
}
static struct platform_driver Myled_platform_driver = {
	.probe  = Myled_probe,
	.remove = __devexit_p(Myled_remove),
	.driver = {
		.name = "Myled_platform_device_driver",
		.owner = THIS_MODULE,
	}
};
static int __init Myled_platform_driver_init(void)
{
    printk("platform_driver_for_Myled init\n");
	return platform_driver_register(&Myled_platform_driver);
}

static void __exit Myled_platform_driver_exit(void)
{
    printk("platform_driver_for_Myled exit\n");
	platform_driver_unregister(&Myled_platform_driver);
}
MODULE_AUTHOR("ZP1015");
MODULE_LICENSE("GPL");
module_param(global_led_major,int,S_IRUGO);
module_init(Myled_platform_driver_init);
module_exit(Myled_platform_driver_exit);
///////////////////////

测试程序：

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h> // open() close()
#include <unistd.h> // read() write()

int main(void)
{
    int fd;

    fd = open("/dev/myled", O_RDWR|O_NDELAY);
    if (fd < 0) {
        printf("open device /lib/module/2.6.32.2/myled error!\n");
    }
    else {
        while(1) {
            printf("led is on!\n");
			write(fd,"1",1);
			sleep(1);//等待1秒再做下一步操作
			printf("led is off!\n");
			write(fd,"0",1);
			sleep(1);
        }
        close(fd);
    }
    return 0;
}

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一步一步学习 Linux 驱动之 platform 机制（tiny210 LED 驱动）

1、概述

2、代码

3、实现结果

4、系统调用方式

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一步一步学习 Linux 驱动之 platform 机制 （tiny210 LED 驱动）

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一步一步学习 Linux 驱动之 platform 机制（tiny210 LED 驱动）

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