驅動分層分離

在前面介紹的輸入子系統中，核心層input.c，裝置層button.c包含硬體相關程式碼，軟體層cdev.c純軟體處理部分。
linux驅動中有很多類似的驅動形式，例如匯流排驅動platform平臺裝置模型
platform.c屬於核心層級別，裝置層device包含硬體相關程式碼，driver層包含驅動層相關程式碼屬於比較固化穩定的軟體程式碼，裝置發生改變只要改變裝置層程式碼，規則上只要滿足驅動層程式碼規則要求，理論上完全不用修改驅動層程式碼。裝置層與軟體層分離的好處就是當裝置發生改變時，只需要修改裝置對應部分程式碼，軟體處理部分不用修改。
平臺裝置模型的一般寫法:

• 構造裝置層結構體
• 註冊裝置結構體
• 構造驅動層結構體
• 註冊驅動結構體
• 核心層進行裝置層與驅動層的匹配
• 匹配成功呼叫相關函式進行兩者掛接

基於JZ2440的LED的平臺裝置框架

驅動層

#include <linux/module.h>
#include <linux/version.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
 

#include <linux/sched.h>
#include <linux/pm.h>
#include <linux/sysctl.h>
#include <linux/proc_fs.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/input.h>
#include <linux/irq.h>
#include <linux/gpio_keys.h>
#include <asm/gpio.h>
 



/* 分配/設定/註冊一個platform_driver */
static int __devinit led_probe(struct platform_device *pdev)
{
    /* 根據platform_dev資源進行ioremap */
    /* 註冊字元裝置   */
    printk("led_probe,found led\n");
    return 0;
}

static int __devexit led_remove(struct platform_device *pdev)
{
    /* 根據platform_dev資源進行iounmap */
    /* 登出字元裝置   */
    printk("led_remove,remove led\n");
    return 0;
}

struct platform_driver led_drv = {
    .probe      = led_probe,
    .remove     = led_remove,
    .driver     = {
        .name   = "myled",
    }
};

static int led_drv_init(void)
{
    platform_driver_register(&led_drv);
    return 0;
}

static void led_drv_exit(void)
{
    platform_driver_unregister(&led_drv);
}

module_init(led_drv_init);
module_exit(led_drv_exit);
MODULE_LICENSE("GPL");

裝置層

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/delay.h>
#include <linux/mtd/mtd.h>

#include <linux/mtd/partitions.h>
#include <linux/input.h>

#include <asm/hardware.h>
#include <asm/mach-types.h>
#include <asm/mach/arch.h>
#include <asm/mach/flash.h>
#include <asm/mach/map.h>


#include <asm/arch/gpio.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <asm/arch/regs-gpio.h>
#include <asm/hardware.h>


/* 分配/設定/註冊一個platform_device */

void led_release(struct device *dev)
{

}
static struct resource led_resource[] = {

    [0]=
    {
        .start      = 0x56000050,
        .end        = 0x56000050 + 8 - 1,
        .flags      = IORESOURCE_MEM,
    },
    [1]=
    {
        .start      = 4,
        .end        = 4,
        .flags      = IORESOURCE_IRQ,
    }
};



static struct platform_device led_dev = {
    .name       = "myled",
    .id     = 0,
    .dev        = { .release=led_release,

    },
    .num_resources  = ARRAY_SIZE(led_resource),
    .resource   = led_resource,
};


static int led_dev_init(void)
{
    platform_device_register(&led_dev);
    return 0;
}

static void led_dev_exit(void)
{
    platform_device_unregister(&led_dev);
}
module_init(led_dev_init);
module_exit(led_dev_exit);
MODULE_LICENSE("GPL");

程式碼執行效果：

[root@JZ2440 015platform]# insmod led_dev.ko
[root@JZ2440 015platform]# insmod led_drv.ko
led_probe,found led
[root@JZ2440 015platform]# rmmod led_drv.ko
led_remove,remove led
[root@JZ2440 015platform]# rmmod led_dev.ko
[root@JZ2440 015platform]#

將功能豐富完整後的驅動

驅動層

#include <linux/module.h>
#include <linux/version.h>

#include <linux/init.h>
#include <linux/fs.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/sched.h>
#include <linux/pm.h>
#include <linux/sysctl.h>
#include <linux/proc_fs.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/input.h>
#include <linux/irq.h>
#include <asm/uaccess.h>
#include <asm/io.h>

#define DEVICENAME "myled"

static unsigned int major=0;
unsigned int pin=0;
static struct class *myclass=NULL;
static struct class_device  *mydev;

static volatile unsigned long *gpfcon=NULL;
static volatile unsigned long *gpfdat=NULL;

#define GPFCON *gpfcon
#define GPFDAT *gpfdat


static int led_open(struct inode *inode, struct file *file)
{
    //配置LED管腳模式
    GPFCON &=~(0x3<<(pin*2));
    GPFCON |= (0x1<<(pin*2));

    //預設燈全部關閉
    GPFDAT |= ((7<<4));
    return 0;
}

static ssize_t led_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos)
{
    int val;

    copy_from_user(&val, buf, count); //    copy_to_user();

    if (val == 1)
    {
        // 點燈
        GPFDAT &= ~(1<<pin);
    }
    else
    {
        // 滅燈
        GPFDAT |= (1<<pin);
    }

    return 0;
}

static struct file_operations my_dev_fops = {
    .owner  =   THIS_MODULE,    /* 這是一個巨集，推向編譯模組時自動建立的__this_module變數 */
    .open   =   led_open,     
    .write  =   led_write,

};


/* 分配/設定/註冊一個platform_driver */
static int __devinit led_probe(struct platform_device *pdev)
{
    /* 根據platform_dev資源進行ioremap */
    struct resource *res;
    res = platform_get_resource(pdev,IORESOURCE_MEM,0);
    gpfcon = ioremap(res->start,res->end-res->start+1);
    gpfdat=gpfcon+1;

    res=platform_get_resource(pdev,IORESOURCE_IRQ,0);
    pin=res->start;

    /* 註冊字元裝置   */
    major = register_chrdev(0,DEVICENAME, &my_dev_fops); // 註冊, 告訴核心
    myclass = class_create(THIS_MODULE,DEVICENAME);
    mydev=class_device_create(myclass, NULL, MKDEV(major,0), NULL, "led");
    printk("led_probe,found led\n");
    return 0;
}

static int __devexit led_remove(struct platform_device *pdev)
{
    /* 根據platform_dev資源進行iounmap */
    /* 登出字元裝置   */
    iounmap(gpfcon);


    class_device_unregister(mydev);
    class_destroy(myclass);
    unregister_chrdev(major, DEVICENAME); // 解除安裝
    printk("led_remove,remove led\n");
    return 0;
}

struct platform_driver led_drv = {
    .probe      = led_probe,
    .remove     = led_remove,
    .driver     = {
        .name   = "myled",
    }
};

static int led_drv_init(void)
{
    platform_driver_register(&led_drv);
    return 0;
}

static void led_drv_exit(void)
{
    platform_driver_unregister(&led_drv);
}

module_init(led_drv_init);
module_exit(led_drv_exit);
MODULE_LICENSE("GPL");

裝置層

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/delay.h>
#include <linux/mtd/mtd.h>

#include <linux/mtd/partitions.h>
#include <linux/input.h>
#include <asm/hardware.h>
#include <asm/mach-types.h>
#include <asm/mach/arch.h>
#include <asm/mach/flash.h>
#include <asm/mach/map.h>
#include <asm/arch/gpio.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <asm/arch/regs-gpio.h>
#include <asm/hardware.h>

/* 分配/設定/註冊一個platform_device */

void led_release(struct device *dev)
{

}
static struct resource led_resource[] = {

    [0]=
    {
        .start      = 0x56000050,
        .end        = 0x56000050 + 8 - 1,
        .flags      = IORESOURCE_MEM,
    },
    [1]=
    {
        .start      = 4,
        .end        = 4,
        .flags      = IORESOURCE_IRQ,
    }
};

static struct platform_device led_dev = {
    .name       = "myled",
    .id     = 0,
    .dev        = {  .release=led_release,},
    .num_resources  = ARRAY_SIZE(led_resource),
    .resource   = led_resource,
};


static int led_dev_init(void)
{
    platform_device_register(&led_dev);
    return 0;
}

static void led_dev_exit(void)
{
    platform_device_unregister(&led_dev);
}
module_init(led_dev_init);
module_exit(led_dev_exit);
MODULE_LICENSE("GPL");

app

#include<stdio.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<unistd.h>
#include<string.h>
int main()
{
    int fd;
    char tmp1='0',tmp2;
    fd = open("/dev/led",O_RDWR);
    if(fd<0)
        printf("led open is fail\n");
    else
        printf("led open success\n");
    write(fd,&tmp1,1);
        sleep(2);
        write(fd,&tmp2,1);
        close(fd);
        return 0;
}