2 device和platform_device
Plarform device会有一个名字用于driver binding（在注册driver的时候会查找driver的目标设备的bus位置，这个过程称为driver binding），另外IRQ以及地址空间等资源也要给出 。
platform_device结构体用来描述设备的名称、资源信息等。该结构被定义在
中，定义原型如下：
16struct platform_device {
17 const char * name; //定义平台设备的名称，此处设备的命名应和相应驱动程序命名一致
18 int id;
19 struct device dev;
20 u32 num_resources;
21 struct resource * resource; //定义平台设备的资源
22};
在这个结构里封装了struct device及struct resource。可知：platform_device由device派生而来，是一种特殊的device。
下面来看一下platform_device结构体中最重要的一个成员struct resource * resource。struct resource被定义在 /ioport.h#L18中，定义原型如下：
14/*
15 * Resources are tree-like, allowing
16 * nesting etc..
17 */
18struct resource {
19 resource_size_t start; //定义资源的起始地址
20 resource_size_t end; //定义资源的结束地址
21 const char *name; //定义资源的名称
22 unsigned long flags; 定义资源的类型，比如MEM，IO，IRQ，DMA类型
23 struct resource *parent, *sibling, *child;
24};
这个结构表示设备所拥有的资源，即I/O端口、I/O映射内存、中断及DMA等。这里的地址指的是物理地址。
另外还需要注意platform_device中的device结构，它详细描述了设备的情况，其为所有设备的基类，定义如下：
422struct device {
423 struct klist klist_children;
424 struct klist_node knode_parent; /* node in sibling list */
425 struct klist_node knode_driver;
426 struct klist_node knode_bus;
427 struct device *parent;
428
429 struct kobject kobj;
430 char bus_id[BUS_ID_SIZE]; /* position on parent bus */
431 struct device_type *type;
432 unsigned is_registered:1;
433 unsigned uevent_suppress:1;
434
435 struct semaphore sem; /* semaphore to synchronize calls to
436 * its driver.
437 */
438
439 struct bus_type *bus; /* type of bus device is on */
440 struct device_driver *driver; /* which driver has allocated this
441 device */
442 void *driver_data; /* data private to the driver */
443 void *platform_data; /* Platform specific data, device
444 core doesn\'t touch it */
445 struct dev_pm_info power;
446
447#ifdef CONFIG_NUMA
448 int numa_node; /* NUMA node this device is close to */
449#endif
450 u64 *dma_mask; /* dma mask (if dma\'able device) */
451 u64 coherent_dma_mask;/* Like dma_mask, but for
452 alloc_coherent mappings as
453 not all hardware supports
454 64 bit addresses for consistent
455 allocations such descriptors. */
456
457 struct device_dma_parameters *dma_parms;
458
459 struct list_head dma_pools; /* dma pools (if dma\'ble) */
460
461 struct dma_coherent_mem *dma_mem; /* internal for coherent mem
462 override */
463 /* arch specific additions */
464 struct dev_archdata archdata;
465
466 spinlock_t devres_lock;
467 struct list_head devres_head;
468
469 /* class_device migration path */
470 struct list_head node;
471 struct class *class;
472 dev_t devt; /* dev_t, creates the sysfs "dev" */
473 struct attribute_group **groups; /* optional groups */
474
475 void (*release)(struct device *dev);
476};
477
3 device_register和platform_device_register