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一、重要知识点：
设备模型由总线、设备、驱动三要素组成。
底层模型决定上层模型，在总线，设备，驱动的结构体中你总是可以看到它们间接或者直接的包含了kobject结构或kset结构。
1.总线
总线是处理器和设备之间的通道，在设备模型中，所有设备都通过总线相连，甚至内部的虚拟“platform”总线。在linux设备模型中，总线由bus_type结构表示。定义在中。
总线描述
struct?bus_type?{??
const?char??????????????????*name;//总线名称??
struct?bus_attribute????????*bus_attrs//总线属性??
struct?device_attribute???*dev_attrs;//设备属性??
struct?driver_attribute????*drv_attrs;//驱动属性??
int?(*match)(struct?device?*dev,?struct?device_driver?*drv);??
int?(*uevent)(struct?device?*dev,?struct?kobj_uevent_env?*env);??
int?(*probe)(struct?device?*dev);??
int?(*remove)(struct?device?*dev);??
void?(*shutdown)(struct?device?*dev);??
int?(*suspend)(struct?device?*dev,?pm_message_t?state);??
int?(*suspend_late)(struct?device?*dev,?pm_message_t?state);??
int?(*resume_early)(struct?device?*dev);??
int?(*resume)(struct?device?*dev);??
struct?dev_pm_ops?*pm;??
struct?bus_type_private?*p;??
};??
struct bus_type {const char *name;//总线名称struct bus_attribute *bus_attrs//总线属性struct device_attribute *dev_attrs;//设备属性struct driver_attribute *drv_attrs;//驱动属性int (*match)(struct device *dev, struct device_driver *drv);int (*uevent)(struct device *dev, struct kobj_uevent_env *env);int (*probe)(struct device *dev);int (*remove)(struct device *dev);void (*shutdown)(struct device *dev);int (*suspend)(struct device *dev, pm_message_t state);int (*suspend_late)(struct device *dev, pm_message_t state);int (*resume_early)(struct device *dev);int (*resume)(struct device *dev);struct dev_pm_ops *pm;struct bus_type_private *p;};
bus_type的bus_type_private?成员
struct?bus_type_private?{??
struct?kset?subsys;??
struct?kset?*drivers_kset;??
struct?kset?*devices_kset;??
struct?klist?klist_devices;??
struct?klist?klist_drivers;??
struct?blocking_notifier_head?bus_notifier;??
unsigned?int?drivers_autoprobe:1;??
struct?bus_type?*bus;??
};??
struct bus_type_private {struct kset subsys;struct kset *drivers_kset;struct kset *devices_kset;struct klist klist_devices;struct klist klist_drivers;struct blocking_notifier_head bus_notifier;unsigned int drivers_autoprobe:1;struct bus_type *bus;};
?
可以看出该结构体中包含了有device和dirver的kset对象。
总线的注册：
int bus_register(structbus_type *bus);
如果成功，新的总线将被添加到系统，在/sys/bus目录下可以看到。
我们在深入看这个函数
int?bus_register(struct?bus_type?*bus)??
{??
int?retval;??
struct?bus_type_private?*priv;??
priv?=?kzalloc(sizeof(struct?bus_type_private),?GFP_KERNEL);??
if?(!priv)??
return?-ENOMEM;??
priv->busbus?=?bus;??
bus->p?=?priv;??
int bus_register(struct bus_type *bus){int retval;struct bus_type_private *priv;priv = kzalloc(sizeof(struct bus_type_private), GFP_KERNEL);if (!priv)return -ENOMEM;priv->bus = bus;bus->p = priv;
BLOCKING_INIT_NOTIFIER_HEAD(&priv->bus_notifier);??
retval?=?kobject_set_name(&priv->subsys.kobj,?"%s",?bus->name);??
if?(retval)??
goto?out;??
priv->subsys.kobj.kset?=?bus_kset;??
priv->subsys.kobj.ktype?=?&bus_ktype;??
priv->drivers_autoprobe?=?1;??
retval?=?kset_register(&priv->subsys);??
if?(retval)??
goto?out;??
retval?=?bus_create_file(bus,?&bus_attr_uevent);??
if?(retval)??
goto?bus_uevent_fail;??
priv->devices_kset?=?kset_create_and_add("devices",?NULL,??
&priv->subsys.kobj);??
if?(!priv->devices_kset)?{??
retval?=?-ENOMEM;??
goto?bus_devices_fail;??
}??
priv->drivers_kset?=?kset_create_and_add("drivers",?NULL,??
&priv->subsys.kobj);??
if?(!priv->drivers_kset)?{??
retval?=?-ENOMEM;??
goto?bus_drivers_fail;??
}??
klist_init(&priv->klist_devices,?klist_devices_get,?klist_devices_put);??
klist_init(&priv->klist_drivers,?NULL,?NULL);??
retval?=?add_probe_files(bus);??
if?(retval)??
goto?bus_probe_files_fail;??
retval?=?bus_add_attrs(bus);??
if?(retval)??
goto?bus_attrs_fail;??
pr_debug("bus:?'%s':?registered\n",?bus->name);??
return?0;??
bus_attrs_fail:??
remove_probe_files(bus);??
bus_probe_files_fail:??
kset_unregister(bus->p->drivers_kset);??
bus_drivers_fail:??
kset_unregister(bus->p->devices_kset);??
bus_devices_fail:??
bus_remove_file(bus,?&bus_attr_uevent);??
bus_uevent_fail:??
kset_unregister(&bus->p->subsys);??
kfree(bus->p);??
out:??
return?retval;??
}??
BLOCKING_INIT_NOTIFIER_HEAD(&priv->bus_notifier);retval = kobject_set_name(&priv->subsys.kobj, "%s", bus->name);if (retval)goto out;priv->subsys.kobj.kset = bus_kset;priv->subsys.kobj.ktype = &bus_ktype;priv->drivers_autoprobe = 1;retval = kset_register(&priv->subsys);if (retval)goto out;retval = bus_create_file(bus, &bus_attr_uevent);if (retval)goto bus_uevent_fail;priv->devices_kset = kset_create_and_add("devices", NULL,&priv->subsys.kobj);if (!priv->devices_kset) {retval = -ENOMEM;goto bus_devices_fail;}priv->drivers_kset = kset_create_and_add("drivers", NULL,&priv->subsys.kobj);if (!priv->drivers_kset) {retval = -ENOMEM;goto bus_drivers_fail;}klist_init(&priv->klist_devices, klist_devices_get, klist_devices_put);klist_init(&priv->klist_drivers, NULL, NULL);retval = add_probe_files(bus);if (retval)goto bus_probe_files_fail;retval = bus_add_attrs(bus);if (retval)goto bus_attrs_fail;pr_debug("bus: '%s': registered\n", bus->name);return 0;bus_attrs_fail:remove_probe_files(bus);bus_probe_files_fail:kset_unregister(bus->p->drivers_kset);bus_drivers_fail:kset_unregister(bus->p->devices_kset);bus_devices_fail:bus_remove_file(bus, &bus_attr_uevent);bus_uevent_fail:kset_unregister(&bus->p->subsys);kfree(bus->p);out:return retval;}
?
从这里
priv->subsys.kobj.kset = bus_kset;
priv->subsys.kobj.ktype = &bus_ktype;
可以看得出总线初始化了自己的kset对象。
总线的删除
void bus_unregister(struct bus_type *bus);
总线的match方法
int (*match)(struct device *dev, struct device_driver *drv);
当一个新设备或者驱动被添加到这个总线时，该方法被调用，用于判断指定的驱动程序是否能处理指定的设备。若可以，则返回非0值。下面的测试程序采用匹配设备的dev->bus_id字符串和驱动的drv->name字符串是否相同来判断驱动是否能处理该设备。
总线uevent方法
int ?(*uevent)(structdevice *dev, char **envp, int num_envp)
在为用户产生热插拔事件之前，这个方法允许总线添加环境变量。
总线属性由结构bus_attribute描述：
struct bus_attribute {
struct attribute??????? attr;
ssize_t (*show)(struct bus_type *bus,char *buf);
ssize_t (*store)(struct bus_type *bus,const char *buf, size_t count);
};
BUS_ATTR(name,mode, show, store)
在编译时创建和初始化bus_attribute结构，它将bus_attr_作为给定前缀来创建总线的真正名称。
如：static BUS_ATTR(version, S_IRUGO, show_bus_version, NULL);
将创建一个bus_attr_version结构体对象。
int bus_create_file(struct bus_type *bus, struct bus_attribute *attr)
创建属性文件
void bus_remove_file(struct bus_type *bus, struct bus_attribute *attr)
删除属性文件
2.设备
struct?device?{??
struct?klist?klist_children;??
struct?klist_nodeknode_parent;/*?node?in?sibling?list?*/??
struct?klist_nodeknode_driver;??
struct?klist_nodeknode_bus;??
struct?device?*parent;??
struct?kobject?kobj;??
char?bus_id[BUS_ID_SIZE];/*?position?on?parent?bus?*/??
unsigned?uevent_suppress:1;??
const?char?*init_name;?/*?initial?name?of?the?device?*/??
struct?device_type*type;??
struct?semaphoresem;/*?semaphore?to?synchronize?calls?to??
*?its?driver.??
*/??
struct?bus_type*bus;/*?type?of?bus?device?is?on?*/??
struct?device_driver?*driver;/*?which?driver?has?allocated?this??
device?*/??
void?*driver_data;/*?data?private?to?the?driver?*/??
void?*platform_data;/*?Platform?specific?data,?device??
core?doesn't?touch?it?*/??
struct?dev_pm_infopower;??
#ifdef?CONFIG_NUMA??
int?numa_node;/*?NUMA?node?this?device?is?close?to?*/??
#endif??
u64?*dma_mask;/*?dma?mask?(if?dma'able?device)?*/??
u64?coherent_dma_mask;/*?Like?dma_mask,?but?for??
alloc_coherent?mappings?as??
not?all?hardware?supports??
64?bit?addresses?for?consistent??
allocations?such?descriptors.?*/??
struct?device_dma_parameters?*dma_parms;??
struct?list_headdma_pools;/*?dma?pools?(if?dma'ble)?*/??
struct?dma_coherent_mem*dma_mem;?/*?internal?for?coherent?mem??
override?*/??
/*?arch?specific?additions?*/??
struct?dev_archdataarchdata;??
dev_t?devt;/*?dev_t,?creates?the?sysfs?"dev"?*/??
spinlock_t?devres_lock;??
struct?list_headdevres_head;??
struct?klist_nodeknode_class;??
struct?class?*class;??
struct?attribute_group**groups;/*?optional?groups?*/??
void?(*release)(struct?device?*dev);??
};??
struct device {struct klist klist_children;struct klist_nodeknode_parent;/* node in sibling list */struct klist_nodeknode_driver;struct klist_nodeknode_bus;struct device *parent;struct kobject kobj;char bus_id[BUS_ID_SIZE];/* position on parent bus */unsigned uevent_suppress:1;const char *init_name; /* initial name of the device */struct device_type*type;struct semaphoresem;/* semaphore to synchronize calls to* its driver.*/struct bus_type*bus;/* type of bus device is on */struct device_driver *driver;/* which driver has allocated thisdevice */void *driver_data;/* data private to the driver */void *platform_data;/* Platform specific data, devicecore doesn't touch it */struct dev_pm_infopower;#ifdef CONFIG_NUMAint numa_node;/* NUMA node this device is close to */#endifu64 *dma_mask;/* dma mask (if dma'able device) */u64 coherent_dma_mask;/* Like dma_mask, but foralloc_coherent mappings asnot all hardware supports64 bit addresses for consistentallocations such descriptors. */struct device_dma_parameters *dma_parms;struct list_headdma_pools;/* dma pools (if dma'ble) */struct dma_coherent_mem*dma_mem; /* internal for coherent memoverride *//* arch specific additions */struct dev_archdataarchdata;dev_t devt;/* dev_t, creates the sysfs "dev" */spinlock_t devres_lock;struct list_headdevres_head;struct klist_nodeknode_class;struct class *class;struct attribute_group**groups;/* optional groups */void (*release)(struct device *dev);};
?
可以看出device结构体中也包含了一个kobject对象
intdevice_register(struct device *dev);
注册设备
vioddevice_unregister(struct device *dev)
注销设备
设备属性由struct device_attribute描述
structdevice_attribute {
struct attribute??????? attr;
ssize_t (*show)(struct device *dev,struct device_attribute *attr,
char *buf);
ssize_t (*store)(struct device *dev,struct device_attribute *attr,
const char *buf, size_t count);
};
int device_create_file(struct device *dev, struct device_attibute *entry)
创建属性文件
void device_remove_file(struct device *dev, struct device_attibute *entry)
删除属性文件
3.驱动
驱动程序由struct device_driver描述：
struct?device_driver?{??
const?char?*name;??
struct?bus_type*bus;??
struct?module?*owner;??
const?char?*mod_name;/*?used?for?built-in?modules?*/??
int?(*probe)?(struct?device?*dev);??
int?(*remove)?(struct?device?*dev);??
void?(*shutdown)?(struct?device?*dev);??
int?(*suspend)?(struct?device?*dev,?pm_message_t?state);??
int?(*resume)?(struct?device?*dev);??
struct?attribute_group?**groups;??
struct?dev_pm_ops?*pm;??
struct?driver_private?*p;??
};??
struct device_driver {const char *name;struct bus_type*bus;struct module *owner;const char *mod_name;/* used for built-in modules */int (*probe) (struct device *dev);int (*remove) (struct device *dev);void (*shutdown) (struct device *dev);int (*suspend) (struct device *dev, pm_message_t state);int (*resume) (struct device *dev);struct attribute_group **groups;struct dev_pm_ops *pm;struct driver_private *p;};
?
在看device_dirver的driver_private 对象
struct driver_private {
struct kobject kobj;
struct klist klist_devices;
struct klist_node knode_bus;
struct module_kobject *mkobj;
struct device_driver *driver;
};
可以看出driver_private结构体中也包含了一个kobject对象。和连接设备的链表。
当总线的match返回非0值，也就是总线找到与驱动相匹配的设备时，驱动的probe的函数将被调用。
当设备从系统总删除是remove被调用。
当系统关机的时候shutdown被调用。
int driver_register(structdevice_driver *drv)
在总线上注册驱动
void driver_unregister(struct device_driver *drv)
载总线上注销驱动
驱动的属性使用structdriver_attribute来描述
structdriver_attribute{
structattribue attr;
ssize_t(*show)(struct device_driver *drv, const char *buf);
ssize_t(*store)(struct device_driver *drv, const char *buf, size_t count);
}
int dirver_create_file(struct device_driver *drv, struct driver_attribute *attr);
创建属性文件
void driver_remove_file struct device_driver *drv, struct driver_attribute *attr);
删除属性文件
二、测试模块
1.BUS
#include?
#include?
#include?
#include?
#include?
MODULE_AUTHOR("David?Xie");??
MODULE_LICENSE("Dual?BSD/GPL");??
static?char?*Version?=?"$Revision:?1.9?{1}quot;;??
static?int?my_match(struct?device?*dev,?struct?device_driver?*driver)??
{??
return?!strncmp(dev->bus_id,?driver->name,?strlen(driver->name));??
}??
static?void?my_bus_release(struct?device?*dev)??
{??
printk(KERN_DEBUG?"my?bus?release\n");??
}??
struct?device?my_bus?=?{??
.bus_id???=?"my_bus0",??
.release??=?my_bus_release??
};??
struct?bus_type?my_bus_type?=?{??
.name?=?"my_bus",??
.match?=?my_match,??
};??
EXPORT_SYMBOL(my_bus);??
EXPORT_SYMBOL(my_bus_type);??
/*??
*?Export?a?simple?attribute.??
*/??
static?ssize_t?show_bus_version(struct?bus_type?*bus,?char?*buf)??
{??
return?snprintf(buf,?PAGE_SIZE,?"%s\n",?Version);??
}??
static?BUS_ATTR(version,?S_IRUGO,?show_bus_version,?NULL);??
static?int?__init?my_bus_init(void)??
{??
int?ret;??
/*注册总线*/??
ret?=?bus_register(&my_bus_type);??
if?(ret)??
return?ret;??
/*创建属性文件*/????
if?(bus_create_file(&my_bus_type,?&bus_attr_version))??
printk(KERN_NOTICE?"Fail?to?create?version?attribute!\n");??
/*注册总线设备*/??
ret?=?device_register(&my_bus);??
if?(ret)??
printk(KERN_NOTICE?"Fail?to?register?device:my_bus!\n");??
return?ret;??
}??
static?void?my_bus_exit(void)??
{??
device_unregister(&my_bus);??
bus_unregister(&my_bus_type);??
}??
module_init(my_bus_init);??
module_exit(my_bus_exit);??
#include #include #include #include #include MODULE_AUTHOR("David Xie");MODULE_LICENSE("Dual BSD/GPL");static char *Version = "$Revision: 1.9 {1}quot;;static int my_match(struct device *dev, struct device_driver *driver){return !strncmp(dev->bus_id, driver->name, strlen(driver->name));}static void my_bus_release(struct device *dev){printk(KERN_DEBUG "my bus release\n");}struct device my_bus = {.bus_id = "my_bus0",.release = my_bus_release};struct bus_type my_bus_type = {.name = "my_bus",.match = my_match,};EXPORT_SYMBOL(my_bus);EXPORT_SYMBOL(my_bus_type);/** 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);static int __init my_bus_init(void){int ret;/*注册总线*/ret = bus_register(&my_bus_type);if (ret)return ret;/*创建属性文件*/if (bus_create_file(&my_bus_type, &bus_attr_version))printk(KERN_NOTICE "Fail to create version attribute!\n");/*注册总线设备*/ret = device_register(&my_bus);if (ret)printk(KERN_NOTICE "Fail to register device:my_bus!\n");return ret;}static void my_bus_exit(void){device_unregister(&my_bus);bus_unregister(&my_bus_type);}module_init(my_bus_init);module_exit(my_bus_exit);
创建一条名为my_bus_type的总线和一个名为my_bus的总线设备，注意总线也是一个设备，也需要注册。
测试结果：
?
2.DEVICE
#include?
#include?
#include?
#include?
#include?
MODULE_AUTHOR("David?Xie");??
MODULE_LICENSE("Dual?BSD/GPL");??
extern?struct?device?my_bus;???
extern?struct?bus_type?my_bus_type;??
/*?Why?need?this??*/??
static?void?my_dev_release(struct?device?*dev)??
{???
}??
struct?device?my_dev?=?{??
.bus?=?&my_bus_type,??
.parent?=?&my_bus,??
.release?=?my_dev_release,??
};??
/*??
*?Export?a?simple?attribute.??
*/??
static?ssize_t?mydev_show(struct?device?*dev,?char?*buf)??
{??
return?sprintf(buf,?"%s\n",?"This?is?my?device!");??
}??
static?DEVICE_ATTR(dev,?S_IRUGO,?mydev_show,?NULL);??
static?int?__init?my_device_init(void)??
{??
int?ret?=?0;??
/*?初始化设备?*/??
strncpy(my_dev.bus_id,?"my_dev",?BUS_ID_SIZE);??
/*注册设备*/??
device_register(&my_dev);??
/*创建属性文件*/??
device_create_file(&my_dev,?&dev_attr_dev);??
return?ret;???
}??
static?void?my_device_exit(void)??
{??
device_unregister(&my_dev);??
}??
module_init(my_device_init);??
module_exit(my_device_exit);??
#include #include #include #include #include MODULE_AUTHOR("David Xie");MODULE_LICENSE("Dual BSD/GPL");extern struct device my_bus;extern struct bus_type my_bus_type;/* Why need this ?*/static void my_dev_release(struct device *dev){}struct device my_dev = {.bus = &my_bus_type,.parent = &my_bus,.release = my_dev_release,};/** Export a simple attribute.*/static ssize_t mydev_show(struct device *dev, char *buf){return sprintf(buf, "%s\n", "This is my device!");}static DEVICE_ATTR(dev, S_IRUGO, mydev_show, NULL);static int __init my_device_init(void){int ret = 0;/* 初始化设备 */strncpy(my_dev.bus_id, "my_dev", BUS_ID_SIZE);/*注册设备*/device_register(&my_dev);/*创建属性文件*/device_create_file(&my_dev, &dev_attr_dev);return ret;}static void my_device_exit(void){device_unregister(&my_dev);}module_init(my_device_init);module_exit(my_device_exit);
注册一个bus_id即名字为my_dev的设备，该设备的bus成员指向上一步创建的my_bus_type总线，parent成员指向上一步创建的my_bus总线设备。
测试结果：
3.DRIVER
#include?
#include?
#include?
#include?
#include?
MODULE_AUTHOR("David?Xie");??
MODULE_LICENSE("Dual?BSD/GPL");??
extern?struct?bus_type?my_bus_type;??
static?int?my_probe(struct?device?*dev)??
{??
printk("Driver?found?device?which?my?driver?can?handle!\n");??
return?0;??
}??
static?int?my_remove(struct?device?*dev)??
{??
printk("Driver?found?device?unpluged!\n");??
return?0;??
}??
struct?device_driver?my_driver?=?{??
.name?=?"my_dev",??
.bus?=?&my_bus_type,??
.probe?=?my_probe,??
.remove?=?my_remove,??
};??
/*??
*?Export?a?simple?attribute.??
*/??
static?ssize_t?mydriver_show(struct?device_driver?*driver,?char?*buf)??
{??
return?sprintf(buf,?"%s\n",?"This?is?my?driver!");??
}??
static?DRIVER_ATTR(drv,?S_IRUGO,?mydriver_show,?NULL);??
static?int?__init?my_driver_init(void)??
{??
int?ret?=?0;??
/*注册驱动*/??
driver_register(&my_driver);??
/*创建属性文件*/??
driver_create_file(&my_driver,?&driver_attr_drv);??
return?ret;???
}??
static?void?my_driver_exit(void)??
{??
driver_unregister(&my_driver);??
}??
module_init(my_driver_init);??
module_exit(my_driver_exit);??
#include #include #include #include #include MODULE_AUTHOR("David Xie");MODULE_LICENSE("Dual BSD/GPL");extern struct bus_type my_bus_type;static int my_probe(struct device *dev){printk("Driver found device which my driver can handle!\n");return 0;}static int my_remove(struct device *dev){printk("Driver found device unpluged!\n");return 0;}struct device_driver my_driver = {.name = "my_dev",.bus = &my_bus_type,.probe = my_probe,.remove= my_remove,};/** Export a simple attribute.*/static ssize_t mydriver_show(struct device_driver *driver, char *buf){return sprintf(buf, "%s\n", "This is my driver!");}static DRIVER_ATTR(drv, S_IRUGO, mydriver_show, NULL);static int __init my_driver_init(void){int ret = 0;/*注册驱动*/driver_register(&my_driver);/*创建属性文件*/driver_create_file(&my_driver, &driver_attr_drv);return ret;}static void my_driver_exit(void){driver_unregister(&my_driver);}module_init(my_driver_init);module_exit(my_driver_exit);
创建一个名为“bus_dev”的驱动，并将bus成员指向第一步创建的my_bus_type总线
测试结果：
?
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