驅動之路-設備模型之上層模型

一、重要知識點：

設備模型由總線、設備、驅動三要素組成。

底層模型決定上層模型，在總線，設備，驅動的結構體中你總是可以看到它們間接或者直接的包含了kobject結構或kset結構。

1.總線

總線是處理器和設備之間的通道，在設備模型中，所有設備都通過總線相連，甚至內部的虛擬“platform”總線。在linux設備模型中，總線由bus_type結構表示。定義在中。

總線描述

struct?bus_type?{??

const?char??????????????????*name;//總線名稱??

struct?bus_attribute????????*bus_attrs//總線屬性??

struct?device_attribute???*dev_attrs;//設備屬性??

struct?driver_attribute????*drv_attrs;//驅動屬性??

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;//總線名稱struct bus_attribute *bus_attrs//總線屬性struct device_attribute *dev_attrs;//設備屬性struct driver_attribute *drv_attrs;//驅動屬性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?成員

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;};
?

可以看出該結構體中包含了有device和dirver的kset對象。

總線的注冊：

int bus_register(structbus_type *bus);

如果成功，新的總線將被添加到系統，在/sys/bus目錄下可以看到。

我們在深入看這個函數

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;}
?

從這里

priv->subsys.kobj.kset = bus_kset;
priv->subsys.kobj.ktype = &bus_ktype;

可以看得出總線初始化了自己的kset對象。

總線的刪除

void bus_unregister(struct bus_type *bus);

總線的match方法

int (*match)(struct device *dev, struct device_driver *drv);

當一個新設備或者驅動被添加到這個總線時，該方法被調用，用于判斷指定的驅動程序是否能處理指定的設備。若可以，則返回非0值。下面的測試程序采用匹配設備的dev->bus_id字符串和驅動的drv->name字符串是否相同來判斷驅動是否能處理該設備。

總線uevent方法

int ?(*uevent)(structdevice *dev, char **envp, int num_envp)

在為用戶產生熱插拔事件之前，這個方法允許總線添加環境變量。

總線屬性由結構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)

在編譯時創建和初始化bus_attribute結構，它將bus_attr_作為給定前綴來創建總線的真正名稱。

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

將創建一個bus_attr_version結構體對象。

int bus_create_file(struct bus_type *bus, struct bus_attribute *attr)

創建屬性文件

void bus_remove_file(struct bus_type *bus, struct bus_attribute *attr)

刪除屬性文件

2.設備

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結構體中也包含了一個kobject對象

intdevice_register(struct device *dev);

注冊設備

vioddevice_unregister(struct device *dev)

注銷設備

設備屬性由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)

創建屬性文件

void device_remove_file(struct device *dev, struct device_attibute *entry)

刪除屬性文件

3.驅動

驅動程序由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 對象

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結構體中也包含了一個kobject對象。和連接設備的鏈表。

當總線的match返回非0值，也就是總線找到與驅動相匹配的設備時，驅動的probe的函數將被調用。

當設備從系統總刪除是remove被調用。

當系統關機的時候shutdown被調用。

int driver_register(structdevice_driver *drv)

在總線上注冊驅動

void driver_unregister(struct device_driver *drv)

載總線上注銷驅動

驅動的屬性使用structdriver_attribute來描述

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);

創建屬性文件

void driver_remove_file struct device_driver *drv, struct driver_attribute *attr);

刪除屬性文件

二、測試模塊

1.BUS

#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;??

/*注冊總線*/??

ret?=?bus_register(&my_bus_type);??

if?(ret)??

return?ret;??

/*創建屬性文件*/????

if?(bus_create_file(&my_bus_type,?&bus_attr_version))??

printk(KERN_NOTICE?"Fail?to?create?version?attribute!\n");??

/*注冊總線設備*/??

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;/*注冊總線*/ret = bus_register(&my_bus_type);if (ret)return ret;/*創建屬性文件*/if (bus_create_file(&my_bus_type, &bus_attr_version))printk(KERN_NOTICE "Fail to create version attribute!\n");/*注冊總線設備*/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);

創建一條名為my_bus_type的總線和一個名為my_bus的總線設備，注意總線也是一個設備，也需要注冊。

測試結果：

2.DEVICE

#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;??

/*?初始化設備?*/??

strncpy(my_dev.bus_id,?"my_dev",?BUS_ID_SIZE);??

/*注冊設備*/??

device_register(&my_dev);??

/*創建屬性文件*/??

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;/* 初始化設備 */strncpy(my_dev.bus_id, "my_dev", BUS_ID_SIZE);/*注冊設備*/device_register(&my_dev);/*創建屬性文件*/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);

注冊一個bus_id即名字為my_dev的設備，該設備的bus成員指向上一步創建的my_bus_type總線，parent成員指向上一步創建的my_bus總線設備。

測試結果：

3.DRIVER

#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;??

/*注冊驅動*/??

driver_register(&my_driver);??

/*創建屬性文件*/??

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;/*注冊驅動*/driver_register(&my_driver);/*創建屬性文件*/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);

創建一個名為“bus_dev”的驅動，并將bus成員指向第一步創建的my_bus_type總線

測試結果：