Linux 驱动之 platform 驱动模型总结 （基于tiny210 平台 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。

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 2015 SCUT.
 *
 * platform  device for led 
 */
#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 2015 SCUT.
 *
 * platform  driver for led 
 */
#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

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 int Myled_open(struct inode * inode,struct file * file)
{
	return 0;
}

static ssize_t Myled_read(struct file * file,const 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;
	devno = MKDEV(global_led_major,0);
	printk(KERN_ALERT"Myled_probe!\n");
	
	if (devno) {
		ret = register_chrdev_region(devno,1,"Myled_platfor_driver");
	} 
	else {
		ret = alloc_chrdev_region(&devno,0,1,"Myled_platfor_driver");
		global_led_major = MAJOR(devno);
	}
	
	if (ret < 0) {
		return ret;
	}
	
	led_cdev = cdev_alloc();
	cdev_init(led_cdev,&led_fops);
	led_cdev->owner = THIS_MODULE;
	err = cdev_add(led_cdev,devno,1);
	led_class = class_create(THIS_MODULE,"Myled_platfor_driver");
	device_create(led_class,NULL,MKDEV(global_led_major,0),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();
	
	if (err) {
		printk(KERN_NOTICE"Error %d adding led_cdev",err);
		return -1;
	} else {
		printk(KERN_NOTICE"platform_driver_for_Myled init ok!\n");
		return 0;	
	}

	
}

static int __devexit Myled_remove(struct platform_device *pdev)
{
	printk("Myled_remove!\n");
	cdev_del(led_cdev);
	iounmap(gpbcon);
	unregister_chrdev_region(MKDEV(global_led_major,0),1);
	device_destroy(led_class, MKDEV(global_led_major,0));
	class_destroy(led_class);
	myled_off();
	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