#1 驱动分离
主机控制器驱动和设备驱动分离，引入中间API；
#2 驱动分层
分为驱动，总线，设备；
总线是Linux内核实现，用户需要实现驱动和设备；
驱动：具体的设备驱动；
设备：设备的属性，包括地址范围等信息；
##2.1 总线
数据结构 bus_type device.h

struct bus_type {
	const char		*name;
	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);//匹配函数
	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);

	int (*num_vf)(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;
};

使用总线时，需要向内核注册

extern int __must_check bus_register(struct bus_type *bus);

##2.2 驱动
数据结构 device_driver device.h

struct device_driver {
	const char		*name;
	struct bus_type		*bus;//记录该驱动属于哪个总线

	struct module		*owner;
	const char		*mod_name;	/* used for built-in modules */

	bool suppress_bind_attrs;	/* disables bind/unbind via sysfs */
	enum probe_type probe_type;

	const struct of_device_id	*of_match_table;
	const struct acpi_device_id	*acpi_match_table;

	int (*probe) (struct device *dev);//驱动和设备匹配后，驱动里面的probe就会执行
	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;
};

使用驱动时，使用如下函数注册：

extern int __must_check driver_register(struct device_driver *drv);

驱动注册过程：

driver_register(struct device_driver *drv)
	bus_add_driver(drv);//将驱动添加到总线
		driver_attach(struct device_driver *drv)	//驱动绑定
			bus_for_each_dev(struct bus_type *bus, struct device *start,void *data, int (*fn)(struct device *, void *))	//遍历总线上的每个设备，fn是函数指针，即为probe
				__driver_attach	//每个设备都调用，查看每个设备是否与驱动匹配
					driver_match_device
						drv->bus->match()==platform_match()
					driver_probe_device(drv,dev)//driver_match_device匹配成功
						really_probe
							drv->probe	//执行driver的probe函数

##2.3 设备
数据结构 device_type 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 this
					   device */
	void		*platform_data;	/* Platform specific data, device
					   core doesn't touch it */
	void		*driver_data;	/* Driver data, set and get with
					   dev_set/get_drvdata */
	struct dev_links_info	links;
	struct dev_pm_info	power;
	struct dev_pm_domain	*pm_domain;

#ifdef CONFIG_GENERIC_MSI_IRQ_DOMAIN
	struct irq_domain	*msi_domain;
#endif
#ifdef CONFIG_PINCTRL
	struct dev_pin_info	*pins;
#endif
#ifdef CONFIG_GENERIC_MSI_IRQ
	struct list_head	msi_list;
#endif

#ifdef CONFIG_NUMA
	int		numa_node;	/* NUMA node this device is close to */
#endif
	const struct dma_map_ops *dma_ops;
	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. */
	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 mem
					     override */
#ifdef CONFIG_DMA_CMA
	struct cma *cma_area;		/* contiguous memory area for dma
					   allocations */
#endif
	/* arch specific additions */
	struct dev_archdata	archdata;

	struct device_node	*of_node; /* associated device tree node */
	struct fwnode_handle	*fwnode; /* firmware 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;
	struct iommu_fwspec	*iommu_fwspec;

	bool			offline_disabled:1;
	bool			offline:1;
};

使用设备时，使用如下函数注册：

extern int __must_check device_register(struct device *dev);

驱动注册过程：

device_add
	bus_probe_device
		device_initial_probe
			__device_attach
				device_bind_driver		//dev->driver非空时（前面已经构造）
					driver_sysfs_add	//创建sysfs中driver和device指向对方的软链接。还有一个与它相对的函数drivers_sysfs_remove()。
					driver_bound		//实际将device加入驱动的设备链表。
				bus_for_each_drv(dev->bus, NULL, &data,__device_attach_driver);//dev->driver为空时
					__device_attach_driver
						driver_match_device
							drv->bus->match()==platform_match()
						driver_probe_device(drv, dev)//driver_match_device匹配成功
							really_probe
								drv->probe	//执行driver的probe函数

总结：驱动与设备匹配成功以后驱动的probe函数就会执行，probe函数就是驱动编写人员实现的。