《Linux总线、设备与驱动》ldd3中demo分析

说明:本文基于Android2.3和Linux2.6;其他版本仅供参考。

Android2.3及Linux2.6.29内核模拟器版本编译与调试

一、古老方式(不支持热插拔)

1.开机前硬件设备已经插入总线;

2.操作系统加载总线驱动,开始扫描设备、并为其申请struct device结构,最后挂入总线驱动devices链表;

3.操作系统加载设备驱动,注册struct device_driver结构,然后去总线驱动的devices链表中遍历没有绑定driver的设备(即struct device中struct device_driver为空的设备),如果匹配、就device_bind_driver。

二、现在方式(支持热插拔)

1.操作系统加载总线驱动;

2.当有硬件插入时;总线驱动扫描到设备、并为其申请struct device,然后去总线驱动的drivers链表去遍历设备驱动;

3.反之,当有设备驱动加载时;总线为其申请struct device_driver,然后去总线驱动的devices链表遍历设备。

总结:由以上可以看出;总线驱动是核心,联系这设备和设备驱动。

三、深入讲解

1.数据结构kernel/include/linux/device.h

总线:struct bus_type;

设备:struct device;

驱动:struct device_driver;

2.关系

总线驱动总会主动去扫描并为其上的设备分配struct device并添加到devices链表中;

反之,总线驱动是被动的接受设备驱动的struct device_driver并添加到drivers链表中。

四、实例-ldd3里边的例子

1.总线驱动的注册与注销

struct bus_type ldd_bus_type = {
	.name = "ldd",
	.match = ldd_match, 
//当一个总线上的新设备或者新驱动被添加时,会一次或者多次调用这个函数;用来匹配总线上的设备和驱动。
/*
static int ldd_match(struct device *dev, struct device_driver *driver){
  //return !(strncmp(dev->bus_id, driver->name, strlen(driver->name));
  return !strncmp(dev->init_name, driver->name, strlen(driver->name));  
  //change by tankai
  //本测试demo,只是判断设备名和驱动名是否一样;实际可能会比较复杂,如USB是通过VID和PID
}
*/
	.uevent  = ldd_hotplug,
};
bus_register(&ldd_bus_type);
bus_unregister(&ldd_bus_type);
struct device ldd_bus = {
	.bus_id   = "ldd0",
	.release  = ldd_bus_release
};
device_register(&ldd_bus);
device_unregister(&ldd_bus);

2.总线驱动提供的设备驱动接口

int register_ldd_driver(struct ldd_driver *driver){
  int ret;
  driver->driver.bus = &ldd_bus_type;
  if (driver->probe)
  driver->driver.probe = lddbus_drv_probe;
  if (driver->remove)
    driver->driver.remove = lddbus_drv_remove;
  if (driver->shutdown)
    driver->driver.shutdown = lddbus_drv_shutdown;
  if (driver->suspend)
    driver->driver.suspend = lddbus_drv_suspend;
  if (driver->resume)
    driver->driver.resume = lddbus_drv_resume;
  ret = driver_register(&driver->driver); 
  //该函数很重要,会去bus上寻找匹配设备(间接调用总线的match接口)、如果匹配成功会调用驱动的探测函数	
  if (ret)
    return ret;
  driver->version_attr.attr.name = "version";
  //driver->version_attr.attr.owner = driver->module;
  driver->version_attr.attr.mode = S_IRUGO;
  driver->version_attr.show = show_version;
  driver->version_attr.store = NULL;
  return driver_create_file(&driver->driver, &driver->version_attr);
}

3.总线在扫描到设备后的注册接口

int register_ldd_device(struct ldd_device *ldddev){
  ldddev->dev.bus = &ldd_bus_type;
  ldddev->dev.parent = &ldd_bus;
  ldddev->dev.release = ldd_dev_release;
  //strncpy(ldddev->dev.bus_id, ldddev->name, BUS_ID_SIZE);
  ldddev->dev.init_name = ldddev->name;  //change by [email protected]
  return device_register(&ldddev->dev);   
  //该函数很重要,会去bus上寻找匹配驱动(间接调用总线的match接口)、如果匹配成功会调用驱动的探测函数
}
五、以下贴上ldd3总线、设备、驱动demo

注意:

因为是模拟事件发生,因此、驱动程序module_init时有设备的注册过程,实际驱动中不需要这部分、是总线轮询或中断导致设备的注册(注意总线注册的设备不会进入设备文件系统下创建设备节点、它只是加入总线的设备链表并在匹配设备驱动时使用;设备文件系统下设备节点的创建,是在设备驱动的探测probe函数中完成)。

1.总线

testbus.c

#include <linux/device.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/string.h>
#include "lddbus.h"

MODULE_AUTHOR("Jonathan Corbet");
MODULE_LICENSE("Dual BSD/GPL");
static char *Version = "$Revision: 1.9 $";

/*
 * Respond to hotplug events.
 */
static int ldd_hotplug(struct device *dev, char **envp, int num_envp,
		char *buffer, int buffer_size)
{
	envp[0] = buffer;
	if (snprintf(buffer, buffer_size, "LDDBUS_VERSION=%s",
			    Version) >= buffer_size)
		return -ENOMEM;
	envp[1] = NULL;
	return 0;
}

/*
 * Match LDD devices to drivers.  Just do a simple name test.
 */
static int ldd_match(struct device *dev, struct device_driver *driver)
{
        //return !(strncmp(dev->bus_id, driver->name, strlen(driver->name));
	return !strncmp(dev->init_name, driver->name, strlen(driver->name));  //change by [email protected]
}


/*
 * The LDD bus device.
 */
static void ldd_bus_release(struct device *dev)
{
	printk(KERN_DEBUG "lddbus release\n");
}
	
/*
 * And the bus type.
 */
struct bus_type ldd_bus_type = {
	.name = "ldd",
	.match = ldd_match,
	//.uevent  = ldd_hotplug,
        .uevent  = ldd_uevent,
};

struct device ldd_bus = {
	.init_name   = "ldd0",
	.release  = ldd_bus_release
};

/*
 * Export a simple attribute.
 */
static ssize_t show_bus_version(struct bus_type *bus, char *buf)
{
	return snprintf(buf, PAGE_SIZE, "%s\n", Version);
}

static BUS_ATTR(version, S_IRUGO, show_bus_version, NULL);



/*
 * LDD devices.
 */

/*
 * For now, no references to LDDbus devices go out which are not
 * tracked via the module reference count, so we use a no-op
 * release function.
 */
static void ldd_dev_release(struct device *dev)
{ 
	printk(KERN_ALERT"lddbus dev release \n");
}

int register_ldd_device(struct ldd_device *ldddev)
{
	ldddev->dev.bus = &ldd_bus_type;
	ldddev->dev.parent = &ldd_bus;
	ldddev->dev.release = ldd_dev_release;
        //strncpy(ldddev->dev.bus_id, ldddev->name, BUS_ID_SIZE);
        ldddev->dev.init_name = ldddev->name;  //change by [email protected]
	return device_register(&ldddev->dev);
}
EXPORT_SYMBOL(register_ldd_device);

void unregister_ldd_device(struct ldd_device *ldddev)
{
	device_unregister(&ldddev->dev);
}
EXPORT_SYMBOL(unregister_ldd_device);

/*
 * Crude driver interface.
 */
static int lddbus_drv_probe(struct device *_dev)
{
	struct ldd_driver *drv = to_ldd_driver(_dev->driver);
	struct ldd_device *dev = to_ldd_device(_dev);

	return drv->probe(dev);
}

static int lddbus_drv_remove(struct device *_dev)
{
	struct ldd_driver *drv = to_ldd_driver(_dev->driver);
	struct ldd_device *dev = to_ldd_device(_dev);

	return drv->remove(dev);
}

static void lddbus_drv_shutdown(struct device *_dev)
{
	struct ldd_driver *drv = to_ldd_driver(_dev->driver);
	struct ldd_device *dev = to_ldd_device(_dev);

	drv->shutdown(dev);
}

static int lddbus_drv_suspend(struct device *_dev, pm_message_t state)
{
	struct ldd_driver *drv = to_ldd_driver(_dev->driver);
	struct ldd_device *dev = to_ldd_device(_dev);

	return drv->suspend(dev, state);
}

static int lddbus_drv_resume(struct device *_dev)
{
	struct ldd_driver *drv = to_ldd_driver(_dev->driver);
	struct ldd_device *dev = to_ldd_device(_dev);

	return drv->resume(dev);
}

/*static*/ int lddbus_kill(struct ldd_device *dev)
{
	printk("lddbus_kill: %s\n",dev->dev.init_name);
	return 0;
}
EXPORT_SYMBOL(lddbus_kill);

static ssize_t show_version(struct device_driver *driver, char *buf)
{
	struct ldd_driver *ldriver = to_ldd_driver(driver);

	sprintf(buf, "%s\n", ldriver->version);
	return strlen(buf);
}
		

int register_ldd_driver(struct ldd_driver *driver)
{
	int ret;

	driver->driver.bus = &ldd_bus_type;
	if (driver->probe)
		driver->driver.probe = lddbus_drv_probe;
	if (driver->remove)
		driver->driver.remove = lddbus_drv_remove;
	if (driver->shutdown)
		driver->driver.shutdown = lddbus_drv_shutdown;
	if (driver->suspend)
		driver->driver.suspend = lddbus_drv_suspend;
	if (driver->resume)
		driver->driver.resume = lddbus_drv_resume;
	ret = driver_register(&driver->driver);
	
	if (ret)
		return ret;
	driver->version_attr.attr.name = "version";
	//driver->version_attr.attr.owner = driver->module;
	driver->version_attr.attr.mode = S_IRUGO;
	driver->version_attr.show = show_version;
	driver->version_attr.store = NULL;
	return driver_create_file(&driver->driver, &driver->version_attr);
}

void unregister_ldd_driver(struct ldd_driver *driver)
{
	driver_unregister(&driver->driver);
}
EXPORT_SYMBOL(register_ldd_driver);
EXPORT_SYMBOL(unregister_ldd_driver);


static int __init ldd_bus_init(void)
{
	int ret;

	ret = bus_register(&ldd_bus_type);
	if (ret)
		return ret;
	if (bus_create_file(&ldd_bus_type, &bus_attr_version))
		printk(KERN_NOTICE "Unable to create version attribute\n");
	ret = device_register(&ldd_bus);
	if (ret)
		printk(KERN_NOTICE "Unable to register ldd0\n");
	return ret;
}

static void ldd_bus_exit(void)
{
	device_unregister(&ldd_bus);
	bus_unregister(&ldd_bus_type);
}

module_init(ldd_bus_init);
module_exit(ldd_bus_exit);

lddbus.h

/*
 * Definitions for the virtual LDD bus.
 *
 * $Id: lddbus.h,v 1.4 2004/08/20 18:49:44 corbet Exp $
 */

//extern struct device ldd_bus;
extern struct bus_type ldd_bus_type;


/*
 * The LDD driver type.
 */

/*
 * A device type for things "plugged" into the LDD bus.
 */

struct ldd_device {
	char *name;
	//struct ldd_driver *driver;
	struct device dev;
};

#define to_ldd_device(x) container_of((x), struct ldd_device, dev)

struct ldd_driver {
	char *version;
	struct module *module;
	int (*probe)(struct ldd_device *);
	int (*remove)(struct ldd_device *);
	void (*shutdown)(struct ldd_device *);
	int (*suspend)(struct ldd_device *, pm_message_t state);
	int (*resume)(struct ldd_device *);	
	struct device_driver driver;
	struct driver_attribute version_attr;
};

#define to_ldd_driver(drv) container_of(drv, struct ldd_driver, driver)

extern int lddbus_kill(struct ldd_device *dev);

extern int register_ldd_device(struct ldd_device *);
extern void unregister_ldd_device(struct ldd_device *);
extern int register_ldd_driver(struct ldd_driver *);
extern void unregister_ldd_driver(struct ldd_driver *);
2.设备与设备驱动

testmini.c

#include <linux/platform_device.h> 
#include <linux/miscdevice.h>

#include <linux/interrupt.h>
//#include <asm/arch/map.h>
#include <asm/io.h>
#include <linux/irq.h>
#include <linux/wait.h>
#include <linux/semaphore.h>

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

#include "lddbus.h"

#include <linux/sched.h>

//指向系统所拥有的资源信息,此信息为公用信息
//可以被多用户共同使用
static struct resource *mini_mem;
static struct resource *mini_irq;
static void __iomem *mini_base;

static unsigned char wq_flag = 0 ; //wait queue 队列的唤醒标志

//设备的数据结构,独立于platform的数据结构,此数据结构
//为驱动开发人员所要重点考虑的
//数据为用户公用的
struct Mini_Dev 
{
	struct miscdevice mdev;
	wait_queue_head_t wq;
	struct semaphore sem;
};

struct Mini_Dev *p_mdev;



static ssize_t s3c2440mini_read(struct file * file, char __user * userbuf,
		size_t count, loff_t * off)
{
	printk ("MINI TEST ..............READ\n");
	return 0;
}

static ssize_t s3c2440mini_write(struct file *file, const char __user *data,
		size_t len, loff_t *ppos)
{
	printk ("MINI TEST ..............write\n");
	return 0;
}

#define IOCTL_MINI_WAITIRQ _IOR('M',1,int)
#define IOCTL_MINI_SENDDATA _IOR('M',2,int)

static int s3c2440mini_ioctl(struct inode *inode, struct file *file,	
		unsigned int cmd, unsigned long arg)
{
	int i;
	switch(cmd)
		{
		case IOCTL_MINI_WAITIRQ:
			wait_event_interruptible(p_mdev->wq, (wq_flag)&0x01);
			wq_flag = 0;
			break;
		case IOCTL_MINI_SENDDATA:
			for ( i = 0 ; i < 0x1000000; i ++)
				{
				writeb(0xff,mini_base);
				}
			break;
		}
	return 0;
}

static int s3c2440mini_open(struct inode *inode, struct file *file)
{
	return 0;
}

static int s3c2440mini_release(struct inode *inode, struct file *file)
{
	printk ("MINI TEST ..............release\n");
	return 0;
}

//设备所具有的file 操作结构是驱动的工作重点
//同时也是设备功能实现的地方
static struct file_operations mini_ops = {
	.owner  	= THIS_MODULE,
	.write 	= s3c2440mini_write,
	.read 	= s3c2440mini_read,
	.unlocked_ioctl		= s3c2440mini_ioctl,
	.release	= s3c2440mini_release,
	.open	= s3c2440mini_open,
};


//kernel interface


//platform 驱动数据结构,提供了探测、移除、挂起、回复和关闭的
//的系统接口,使系统设备更加的规范
//.driver 挂接着设备的数据结构和资源信息,这些信息已经提前被
//注册到系统里,只有在.name相同的情况下调用platform_driver_register才能
//注册成功

static struct ldd_device mini_device = {
	.name 	= "mini",
};

static int mini_probe (struct ldd_device * dev)
{
	printk("mini_probe %s\n",dev->name);
	lddbus_kill(dev);
	return 0;
}


static struct ldd_driver mini_driver = {
	.version = "$Revision: 1.21 $",
	.module = THIS_MODULE,
	.probe	= mini_probe,
	.driver = {
		.name = "mini",
	},
};


static int __init mini_init(void) 
{ 
	register_ldd_device(&mini_device);
	return register_ldd_driver(&mini_driver);
} 

static void __exit mini_exit(void) 
{ 
	unregister_ldd_device(&mini_device);
	return 	unregister_ldd_driver(&mini_driver);
} 

module_init(mini_init); 
module_exit(mini_exit); 

MODULE_AUTHOR("ljf");
MODULE_LICENSE("Dual BSD/GPL");

Makefile

	obj-m := testlddbus.o testmini.o
	PWD := $(shell pwd)
	KERNELDIR := /usr/src/linux-headers-3.0.0-26-generic/
default:
	$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
#	cp -rf mini.ko ../module/
#	cp -rf lddbus.ko ../module/
clean:
	rm *.mod.c *.o *.ko *.bak modules.* Module.*

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