《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 [e-mail]  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 [e-mail]}/* * 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 [e-mail] 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.oPWD := $(shell pwd)KERNELDIR := /usr/src/linux-headers-3.0.0-26-generic/default:$(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.*