到这里，我该恭喜你，因为你已经能够编写Linux内核模块了。这种感觉很美妙，不是吗?你可以嘲笑秦皇汉武略输文采唐宗宋祖稍逊风骚，还可以嘲笑一代天骄成吉思汗只识弯弓射大雕了。是的，阿娇姐姐告诉我们，只要我喜欢，还有什么不可以。
日后我们会看到，2.6内核中，每个模块都是以module_init开始，以module_exit结束。对大多数人来说没有必要知道这是为什么，记住 就可以了，对大多数人来说，这就像是1+1为什么等于2一样，就像是两点之间最短的是直线，不需要证明，如果一定要证明两点之间直线最短，可以扔一块骨头 在B点，让一条狗从A点出发，你会发现狗走的是直线，是的，狗都知道，咱还能不知道吗?对于驱动开发来说，设备模型的理解是根本，毫不夸张得说，理解了设备模型，再去看那些五花八门的驱动程序，你会发现自己站在了另一个高度，从而有了一种俯视的感觉，就像凤姐俯视知音和故事会，韩峰同志俯视女下属。
顾名而思义就知道设备模型是关于设备的模型，既不是任小强们的房模，也不是张导的炮模。对咱们写驱动的和不写驱动的人来说，设备的概念就是总线和与 其相连的各种设备了。电脑城的IT工作者都会知道设备是通过总线连到计算机上的，而且还需要对应的驱动才能用，可是总线是如何发现设备的，设备又是如何和 驱动对应起来的，它们经过怎样的艰辛才找到命里注定的那个他，它们的关系如何，白头偕老型的还是朝三暮四型的，这些问题就不是他们关心的了，而是咱们需要关心的。在房市股市千锤百炼的咱们还能够惊喜的发现，这些疑问的中心思想中心词汇就是总线、设备和驱动，没错，它们就是咱们这里要聊的Linux设备模型的名角。
总线、设备、驱动，也就是bus、device、driver，既然是名角，在内核里都会有它们自己专属的结构，在include/linux/device.h里定义。
52 struct bus_type {
53 const char * name;
54 struct module * owner;
55
56 struct kset subsys;
57 struct kset drivers;
58 struct kset devices;
59 struct klist klist_devices;
60 struct klist klist_drivers;
61
62 struct blocking_notifier_head bus_notifier;
63
64 struct bus_attribute * bus_attrs;
65 struct device_attribute * dev_attrs;
66 struct driver_attribute * drv_attrs;
67 struct bus_attribute drivers_autoprobe_attr;
68 struct bus_attribute drivers_probe_attr;
69
70 int (*match)(struct device * dev, struct device_driver * drv);
71 int (*uevent)(struct device *dev, char **envp,
72 int num_envp, char *buffer, int buffer_size);
73 int (*probe)(struct device * dev);
74 int (*remove)(struct device * dev);
75 void (*shutdown)(struct device * dev);
76
77 int (*suspend)(struct device * dev, pm_message_t state);
78 int (*suspend_late)(struct device * dev, pm_message_t state);
79 int (*resume_early)(struct device * dev);
80 int (*resume)(struct device * dev);
81
82 unsigned int drivers_autoprobe:1;
83 };
124 struct device_driver {
125 const char * name;
126 struct bus_type * bus;
127
128 struct kobject kobj;
129 struct klist klist_devices;
130 struct klist_node knode_bus;
131
132 struct module * owner;
133 const char * mod_name; /* used for built-in modules */
134 struct module_kobject * mkobj;
135
136 int (*probe) (struct device * dev);
137 int (*remove) (struct device * dev);
138 void (*shutdown) (struct device * dev);
139 int (*suspend) (struct device * dev, pm_message_t state);
140 int (*resume) (struct device * dev);
141 };
407 struct device {
408 struct klist klist_children;
409 struct klist_node knode_parent; /* node in sibling list */
410 struct klist_node knode_driver;
411 struct klist_node knode_bus;
412 struct device *parent;
413
414 struct kobject kobj;
415 char bus_id[BUS_ID_SIZE]; /* position on parent bus */
416 struct device_type *type;
417 unsigned is_registered:1;
418 unsigned uevent_suppress:1;
419
420 struct semaphore sem; /* semaphore to synchronize calls to
421 * its driver.
422 */
423
424 struct bus_type * bus; /* type of bus device is on */
425 struct device_driver *driver; /* which driver has allocated this
426 device */
427 void *driver_data; /* data private to the driver */
428 void *platform_data; /* Platform specific data, device
429 core doesn't touch it */
430 struct dev_pm_info power;
431
432 #ifdef CONFIG_NUMA
433 int numa_node; /* NUMA node this device is close to */
434 #endif
435 u64 *dma_mask; /* dma mask (if dma'able device) */
436 u64 coherent_dma_mask;/* Like dma_mask, but for
437 alloc_coherent mappings as
438 not all hardware supports
439 64 bit addresses for consistent
440 allocations such descriptors. */
441
442 struct list_head dma_pools; /* dma pools (if dma'ble) */
443
444 struct dma_coherent_mem *dma_mem; /* internal for coherent mem
445 override */
446 /* arch specific additions */
447 struct dev_archdata archdata;
448
449 spinlock_t devres_lock;
450 struct list_head devres_head;
451
452 /* class_device migration path */
453 struct list_head node;
454 struct class *class;
455 dev_t devt; /* dev_t, creates the sysfs "dev" */
456 struct attribute_group **groups; /* optional groups */
457
458 void (*release)(struct device * dev);
459 };
53 const char * name;
54 struct module * owner;
55
56 struct kset subsys;
57 struct kset drivers;
58 struct kset devices;
59 struct klist klist_devices;
60 struct klist klist_drivers;
61
62 struct blocking_notifier_head bus_notifier;
63
64 struct bus_attribute * bus_attrs;
65 struct device_attribute * dev_attrs;
66 struct driver_attribute * drv_attrs;
67 struct bus_attribute drivers_autoprobe_attr;
68 struct bus_attribute drivers_probe_attr;
69
70 int (*match)(struct device * dev, struct device_driver * drv);
71 int (*uevent)(struct device *dev, char **envp,
72 int num_envp, char *buffer, int buffer_size);
73 int (*probe)(struct device * dev);
74 int (*remove)(struct device * dev);
75 void (*shutdown)(struct device * dev);
76
77 int (*suspend)(struct device * dev, pm_message_t state);
78 int (*suspend_late)(struct device * dev, pm_message_t state);
79 int (*resume_early)(struct device * dev);
80 int (*resume)(struct device * dev);
81
82 unsigned int drivers_autoprobe:1;
83 };
124 struct device_driver {
125 const char * name;
126 struct bus_type * bus;
127
128 struct kobject kobj;
129 struct klist klist_devices;
130 struct klist_node knode_bus;
131
132 struct module * owner;
133 const char * mod_name; /* used for built-in modules */
134 struct module_kobject * mkobj;
135
136 int (*probe) (struct device * dev);
137 int (*remove) (struct device * dev);
138 void (*shutdown) (struct device * dev);
139 int (*suspend) (struct device * dev, pm_message_t state);
140 int (*resume) (struct device * dev);
141 };
407 struct device {
408 struct klist klist_children;
409 struct klist_node knode_parent; /* node in sibling list */
410 struct klist_node knode_driver;
411 struct klist_node knode_bus;
412 struct device *parent;
413
414 struct kobject kobj;
415 char bus_id[BUS_ID_SIZE]; /* position on parent bus */
416 struct device_type *type;
417 unsigned is_registered:1;
418 unsigned uevent_suppress:1;
419
420 struct semaphore sem; /* semaphore to synchronize calls to
421 * its driver.
422 */
423
424 struct bus_type * bus; /* type of bus device is on */
425 struct device_driver *driver; /* which driver has allocated this
426 device */
427 void *driver_data; /* data private to the driver */
428 void *platform_data; /* Platform specific data, device
429 core doesn't touch it */
430 struct dev_pm_info power;
431
432 #ifdef CONFIG_NUMA
433 int numa_node; /* NUMA node this device is close to */
434 #endif
435 u64 *dma_mask; /* dma mask (if dma'able device) */
436 u64 coherent_dma_mask;/* Like dma_mask, but for
437 alloc_coherent mappings as
438 not all hardware supports
439 64 bit addresses for consistent
440 allocations such descriptors. */
441
442 struct list_head dma_pools; /* dma pools (if dma'ble) */
443
444 struct dma_coherent_mem *dma_mem; /* internal for coherent mem
445 override */
446 /* arch specific additions */
447 struct dev_archdata archdata;
448
449 spinlock_t devres_lock;
450 struct list_head devres_head;
451
452 /* class_device migration path */
453 struct list_head node;
454 struct class *class;
455 dev_t devt; /* dev_t, creates the sysfs "dev" */
456 struct attribute_group **groups; /* optional groups */
457
458 void (*release)(struct device * dev);
459 };
