Linux设备模型（二）上层容器

        linux提供了新的设备模型：总线（bus）、设备（device）、驱动（driver）。其中总线是处理器与设备之间通道，在设备模型中，所有的设备都通过总线相连；设备是对于一个设备的详细信息描述，驱动是设备的相关驱动。其基本关系如下：bus 相当于一个容器，是device 和device_driver 的管理机构，它包含了一个device 集合和一个driver 集合。其中，device集合包含了挂在该总线下的所有设备，这些设备通过链表链接起来；driver集合包含了挂在该总线下的所有驱动程序，这些驱动程序通过链表链接起来。

1.总线bus 

     总线是处理器和设备之间的通道，在设备模型中,所有的设备都通过总线相连,甚至是内部的虚拟“platform”总线。在Linux设备模型中,总线由bus_type结构表示,定义在<linux/device.h>

struct bus_type {const char*name;/*总线名称*/const char*dev_name;//用于subsystems枚举设备struct device*dev_root;//默认的父设备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 (*resume)(struct device *dev);const struct dev_pm_ops *pm;struct iommu_ops *iommu_ops;struct subsys_private *p;};

总线注册/删除

总线的注册使用：bus_register(struct bus_type * bus) 若成功，新的总线将被添加进系统，并可在sysfs 的/sys/bus 下看到。

总线的删除使用：void bus_unregister(struct bus_type *bus) 

总线方法

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，则返回非零值。

int (*uevent)(struct device *dev,char **envp,int num_envp,char *buffer,int buffer_size) 在为用户空间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

总线属性由结构bus_attribute 描述，定义如下:

struct bus_attribute {struct attributeattr;ssize_t (*show)(struct bus_type *bus, char *buf);ssize_t (*store)(struct bus_type *bus, const char *buf, size_t count);};

属性方法：

int bus_create_file(struct bus_type *bus,struct bus_attribute *attr)  创建属性

void bus_remove_file(struct bus_type*bus,struct bus_attribute *attr) 删除属性

2.关于设备device

struct device {struct device*parent;/*设备的"父"设备，该设备所属的设备，通常一个父设备是某种总线或者主控制器。如果parent 是NULL, 则该设备是顶层设备，较少见*/ struct device_private*p;/*该设备驱动使用的私有数据成员*/struct kobject kobj;/*内嵌的kobject*/const char*init_name; /* initial name of the device */const struct device_type *type;//设备类型，用于识别设备类型和携带特定类型的信息。struct mutexmutex;/* mutex 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*platform_data;/* Platform specific data, device   core doesn't touch it */struct dev_pm_infopower;struct dev_pm_domain*pm_domain;#ifdef CONFIG_NUMAintnuma_node;/* NUMA node this device is close to */#endifu64*dma_mask;/* dma mask (if dma'able device) */u64coherent_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 */#ifdef CONFIG_CMAstruct cma *cma_area;/* contiguous memory area for dma   allocations */#endif/* arch specific additions */struct dev_archdataarchdata;struct device_node*of_node; /* associated device tree node */dev_tdevt;/* dev_t, creates the sysfs "dev" */u32id;/* device instance */spinlock_tdevres_lock;struct list_headdevres_head;struct klist_nodeknode_class;struct class*class;const struct attribute_group **groups;/* optional groups */void(*release)(struct device *dev);struct iommu_group*iommu_group;};

注册设备：int device_register(sruct device *dev)

注销设备：void device_unregister(struct device *dev);

设备属性

设备属性由struct device_attribute 描述：

struct device_attribute {struct attributeattr;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);};

创建属性：int device_create_file(struct device*device, struct device_attribute * entry)

删除属性：void device_remove_file(struct device *dev, struct device_attribute * attr)

3.关于驱动driver

struct device_driver {const char*name;/*驱动程序的名字( 体现在sysfs 中)*/struct bus_type*bus;/*驱动程序所在的总线*/struct module*owner;const char*mod_name;/* used for built-in modules */bool suppress_bind_attrs;/* disables bind/unbind via sysfs */const struct of_device_id*of_match_table;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);const struct attribute_group **groups;const struct dev_pm_ops *pm;struct driver_private *p;};

驱动注册/注销

int driver_register(struct device_driver *drv)   注册驱动

void driver_unregister(struct device_driver *drv) 注销驱动

驱动的属性使用struct driver_attribute 来描述：

struct driver_attribute {struct attribute attr;ssize_t (*show)(struct device_driver *driver, char *buf);ssize_t (*store)(struct device_driver *driver, const char *buf, size_t count);};

创建属性int driver_create_file(struct device_driver * drv,struct driver_attribute * attr) 

删除属性：void driver_remove_file(struct device_driver * drv,struct driver_attribute * attr)