§1 bus
系統(tǒng)中總線由struct bus_type描述，定義為：

include/linux/device.h

struct bus_type {const char		*name;總線類型的名稱const char		*dev_name;struct device		*dev_root;struct device_attribute	*dev_attrs;	/* use dev_groups instead */const struct attribute_group **bus_groups;const struct attribute_group **dev_groups;const struct attribute_group **drv_groups;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 (*online)(struct device *dev);int (*offline)(struct device *dev);int (*suspend)(struct device *dev, pm_message_t state);int (*resume)(struct device *dev);const struct dev_pm_ops *pm;const struct iommu_ops *iommu_ops;struct subsys_private *p;struct lock_class_key lock_key;
};

每個bus_type對象都對應/sys/bus目錄下的一個子目錄，如PCI總線類型對應于/sys/bus/pci。在每個這樣的目錄下都存在兩個子目錄：devices和drivers(dev_groups和drv_groups)。其中devices子目錄描述連接在該總線上的所有設備，而drivers目錄則描述與該總線關聯(lián)的所有驅(qū)動程序。與device_driver對象類似，bus_type結(jié)構(gòu)還包含幾個函數(shù)（match()、hotplug()等）處理相應的熱插拔、即插即拔和電源管理事件。

§2 device
系統(tǒng)中的任一設備在設備模型中都由一個device對象描述，其對應的數(shù)據(jù)結(jié)構(gòu)struct device
定義為：

include/linux/device.h

struct device {struct device		*parent;struct device_private	*p;struct kobject kobj;const char		*init_name; /* initial name of the device */const struct device_type *type;struct mutex		mutex;	/* 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 thisdevice */void		*platform_data;	/* Platform specific data, devicecore doesn't touch it */void		*driver_data;	/* Driver data, set and get withdev_set/get_drvdata */struct dev_pm_info	power;struct dev_pm_domain	*pm_domain;#ifdef CONFIG_PINCTRLstruct dev_pin_info	*pins;
#endif#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. */unsigned long	dma_pfn_offset;struct device_dma_parameters *dma_parms;struct list_head	dma_pools;	/* dma pools (if dma'ble) */struct dma_coherent_mem	*dma_mem; /* internal for coherent memoverride */
#ifdef CONFIG_DMA_CMAstruct cma *cma_area;		/* contiguous memory area for dmaallocations */
#endif/* arch specific additions */struct dev_archdata	archdata;struct device_node	*of_node; /* associated device tree node */struct acpi_dev_node	acpi_node; /* associated ACPI device node */dev_t			devt;	/* dev_t, creates the sysfs "dev" */u32			id;	/* device instance */spinlock_t		devres_lock;struct list_head	devres_head;struct klist_node	knode_class;struct class		*class;const struct attribute_group **groups;	/* optional groups */void	(*release)(struct device *dev);struct iommu_group	*iommu_group;bool			offline_disabled:1;bool			offline:1;
};

parent域指向父對象。Device對象還內(nèi)嵌一個kobject對象，用于引用計數(shù)管理并通過它實現(xiàn)設備層次結(jié)構(gòu)。Driver域指向管理該設備的驅(qū)動程序?qū)ο?#xff0c;而driver data則是提供給驅(qū)動程序的數(shù)據(jù)。Bus域描述設備所連接的總線類型。

內(nèi)核提供了相應的函數(shù)用于操作device對象。其中device_register()函數(shù)將一個新的device對象插入設備模型，并自動在/sys/devices下創(chuàng)建一個對應的目錄。device_unregister()完成相反的操作，注銷設備對象。get_device()和put_device()分別增加與減少設備對象的引用計數(shù)。通常device結(jié)構(gòu)不單獨使用，而是包含在更大的結(jié)構(gòu)中作為一個子結(jié)構(gòu)使用，比如描述PCI設備的struct pci_dev，還有我們ldd_dev,其中的dev域就是一個device對象。

§3. driver
系統(tǒng)中的每個驅(qū)動程序由一個device_driver對象描述，對應的數(shù)據(jù)結(jié)構(gòu)定義為：

include/linux/device.h

struct device_driver {const char		*name;設備驅(qū)動程序的名稱struct bus_type		*bus;該驅(qū)動所管理的設備掛接的總線類型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;const struct acpi_device_id	*acpi_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;
};

內(nèi)核提供類似的函數(shù)用于操作device_driver對象，如get_driver()增加引用計數(shù)，driver_register()用于向設備模型插入新的driver對象，同時在sysfs文件系統(tǒng)中創(chuàng)建對應的目錄。device_driver()結(jié)構(gòu)還包括幾個函數(shù)，用于處理熱拔插、即插即用和電源管理事件。

可能你面對剛剛列舉出來的一些列數(shù)據(jù)結(jié)構(gòu)，感到很苦惱，很莫名其妙。沒關系，我接下來講個例子您就明白了。

總結(jié)

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