嵌入式Linux驱动复习（4）分层思想写imx6ull的LED驱动程序

本节的重点是我们要理解如何分层的实现驱动程序

 对于LED驱动，我们想要什么样的接口？

用分层的思想写驱动程序，才能使得驱动程序支持多个板子

1. 把驱动拆分为通用的框架(leddrv.c)、具体的硬件操作(board_X.c)：

 

2. 以面向对象的思想，改进代码：

抽象出一个结构体：

 

 每个单板相关的board_X.c实现自己的led_operations结构体，供上层的leddrv.c调用：

 

led_opr.h

#ifndef _LED_OPR_H
#define _LED_OPR_H

//函数指针？？？反正是面向对象思想的写法 
struct led_operations {
	int (*init) (int which); /* 初始化LED, which-哪个LED */       
	int (*ctl) (int which, char status); /* 控制LED, which-哪个LED, status:1-亮,0-灭 */
};

struct led_operations *get_board_led_opr(void); //定义了一个结构体指针函数


#endif

board_demo.c

#include <linux/module.h>

#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/mutex.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/kmod.h>
#include <linux/gfp.h>
#include "led_opr.h"

static int board_demo_led_init (int which) /* 初始化LED, which-哪个LED */	   
{
	
	printk("%s %s line %d, led %d\n", __FILE__, __FUNCTION__, __LINE__, which);
	return 0;
}

static int board_demo_led_ctl (int which, char status) /* 控制LED, which-哪个LED, status:1-亮,0-灭 */
{
	printk("%s %s line %d, led %d, %s\n", __FILE__, __FUNCTION__, __LINE__, which, status ? "on" : "off");
	return 0;
}

static struct led_operations board_demo_led_opr = {
	.init = board_demo_led_init,
	.ctl  = board_demo_led_ctl,
};

struct led_operations *get_board_led_opr(void）//leddrv中调用，让主函数能调用上面定义的函数
{
	return &board_demo_led_opr;
}

leddrv.c

#include <linux/module.h>

#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/mutex.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/kmod.h>
#include <linux/gfp.h>

#include "led_opr.h"

#define LED_NUM 2

/* 1. 确定主设备号                                                                 */
static int major = 0;
static struct class *led_class;
struct led_operations *p_led_opr;


#define MIN(a, b) (a < b ? a : b)

/* 3. 实现对应的open/read/write等函数，填入file_operations结构体                   */
static ssize_t led_drv_read (struct file *file, char __user *buf, size_t size, loff_t *offset)
{
	printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
	return 0;
}

/* write(fd, &val, 1); */
static ssize_t led_drv_write (struct file *file, const char __user *buf, size_t size, loff_t *offset)
{
	int err;
	char status;
	struct inode *inode = file_inode(file);   //从file里面的到inode
	int minor = iminor(inode);  //得出次设备号
	
	printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
	err = copy_from_user(&status, buf, 1);

	/* 根据次设备号和status控制LED */
	p_led_opr->ctl(minor, status);
	
	return 1;
}

static int led_drv_open (struct inode *node, struct file *file)
{
	int minor = iminor(node);
	
	printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
	/* 根据次设备号初始化LED */
	p_led_opr->init(minor);
	
	return 0;
}

static int led_drv_close (struct inode *node, struct file *file)
{
	printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
	return 0;
}

/* 2. 定义自己的file_operations结构体                                              */
static struct file_operations led_drv = {
	.owner	 = THIS_MODULE,
	.open    = led_drv_open,
	.read    = led_drv_read,
	.write   = led_drv_write,
	.release = led_drv_close,
};

/* 4. 把file_operations结构体告诉内核：注册驱动程序                                */
/* 5. 谁来注册驱动程序啊？得有一个入口函数：安装驱动程序时，就会去调用这个入口函数 */
static int __init led_init(void)
{
	int err;
	int i;
	
	printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
	major = register_chrdev(0, "100ask_led", &led_drv);  /* /dev/led */


	led_class = class_create(THIS_MODULE, "100ask_led_class");
	err = PTR_ERR(led_class);
	if (IS_ERR(led_class)) {
		printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
		unregister_chrdev(major, "100ask_led");
		return -1;
	}

	for (i = 0; i < LED_NUM; i++)
		device_create(led_class, NULL, MKDEV(major, i), NULL, "100ask_led%d", i); /* /dev/100ask_led0,1,... */

	p_led_opr = get_board_led_opr();   //的到具体单板的指针，可以用来调用init和ctrl函数 
	
	return 0;
}

/* 6. 有入口函数就应该有出口函数：卸载驱动程序时，就会去调用这个出口函数           */
static void __exit led_exit(void)
{
	int i;
	printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);

	for (i = 0; i < LED_NUM; i++)
		device_destroy(led_class, MKDEV(major, i)); /* /dev/100ask_led0,1,... */

	device_destroy(led_class, MKDEV(major, 0));
	class_destroy(led_class);
	unregister_chrdev(major, "100ask_led");
}


/* 7. 其他完善：提供设备信息，自动创建设备节点                                     */

module_init(led_init);
module_exit(led_exit);

MODULE_LICENSE("GPL");