platform的probe函数是何时被调用的

   这几天搞TI的vpfe，里面设备的注册使用platform，平台设备注册方式来注册的。一直都知道

112 struct device_driver { 113 const char * name; 114 struct bus_type * bus; 115 116 struct completion unloaded; 117 struct kobject kobj; 118 struct klist klist_devices; 119 struct klist_node knode_bus; 120 121 struct module * owner; 122 123 int (*probe) (struct device * dev); 124 int (*remove) (struct device * dev); 125 void (*shutdown) (struct device * dev); 126 int (*suspend) (struct device * dev, pm_message_t state); 127 int (*resume) (struct device * dev); 128 };

里的probe函数，但是不知道是何时被调用的。经过跟踪代码，在module_init(vpfe_init);模块初始化的时候，vpfe_init函数中调用了

4775 /* Register driver to the kernel */ 4776 err = driver_register(&vpfe_driver);

这里
 err = driver_register(&vpfe_driver);
的原型为：

171 int driver_register(struct device_driver * drv) 172 { 173 if ((drv->bus->probe && drv->probe) || 174 (drv->bus->remove && drv->remove) || 175 (drv->bus->shutdown && drv->shutdown)) { 176 printk(KERN_WARNING "Driver '%s' needs updating - please use bus_type methods/n", drv->name); 177 } 178 klist_init(&drv->klist_devices, klist_devices_get, klist_devices_put); 179 init_completion(&drv->unloaded); 180 return bus_add_driver(drv); 181 }

跟踪bus_add_driver(drv);得到bus_add_driver(struct device_driver * drv)的原型：

479 int bus_add_driver(struct device_driver * drv) 480 { 481 struct bus_type * bus = get_bus(drv->bus); 482 int error = 0; 483 484 if (bus) { 485 pr_debug("bus %s: add driver %s/n", bus->name, drv->name); 486 error = kobject_set_name(&drv->kobj, "%s", drv->name); 487 if (error) { 488 put_bus(bus); 489 return error; 490 } 491 drv->kobj.kset = &bus->drivers; 492 if ((error = kobject_register(&drv->kobj))) { 493 put_bus(bus); 494 return error; 495 } 496 497 driver_attach(drv); 498 klist_add_tail(&drv->knode_bus, &bus->klist_drivers); 499 module_add_driver(drv->owner, drv); 500 501 driver_add_attrs(bus, drv); 502 add_bind_files(drv); 503 } 504 return error; 505 } 其中190 void driver_attach(struct device_driver * drv) 191 { 192 bus_for_each_dev(drv->bus, NULL, drv, __driver_attach); 193 } __driver_attach是一个函数，原型： 155 static int __driver_attach(struct device * dev, void * data) 156 { 157 struct device_driver * drv = data; 158 159 /* 160 * Lock device and try to bind to it. We drop the error 161 * here and always return 0, because we need to keep trying 162 * to bind to devices and some drivers will return an error 163 * simply if it didn't support the device. 164 * 165 * driver_probe_device() will spit a warning if there 166 * is an error. 167 */ 168 169 if (dev->parent) /* Needed for USB */ 170 down(&dev->parent->sem); 171 down(&dev->sem); 172 if (!dev->driver) 173 driver_probe_device(drv, dev); 174 up(&dev->sem); 175 if (dev->parent) 176 up(&dev->parent->sem); 177 178 return 0; 179 }

这里调用了 driver_probe_device(drv, dev);
原型：

76 int driver_probe_device(struct device_driver * drv, struct device * dev) 77 { 78 int ret = 0; 79 80 if (drv->bus->match && !drv->bus->match(dev, drv)) 81 goto Done; 82 83 pr_debug("%s: Matched Device %s with Driver %s/n", 84 drv->bus->name, dev->bus_id, drv->name); 85 dev->driver = drv; 86 if (dev->bus->probe) { 87 ret = dev->bus->probe(dev); 88 if (ret) { 89 dev->driver = NULL; 90 goto ProbeFailed; 91 } 92 } else if (drv->probe) { 93 ret = drv->probe(dev); 94 if (ret) { 95 dev->driver = NULL; 96 goto ProbeFailed; 97 } 98 } 99 device_bind_driver(dev); 100 ret = 1; 101 pr_debug("%s: Bound Device %s to Driver %s/n", 102 drv->bus->name, dev->bus_id, drv->name); 103 goto Done; 104 105 ProbeFailed: 106 if (ret == -ENODEV || ret == -ENXIO) { 107 /* Driver matched, but didn't support device 108 * or device not found. 109 * Not an error; keep going. 110 */ 111 ret = 0; 112 } else { 113 /* driver matched but the probe failed */ 114 printk(KERN_WARNING 115 "%s: probe of %s failed with error %d/n", 116 drv->name, dev->bus_id, ret); 117 } 118 Done: 119 return ret; 120 }   

可以看出是先调用了总线的probe方法，接着调用了设备的probe方法。

总之一句话，probe函数作为driver的最基本的函数指针，一旦你的device和driver匹配（match，由总线（bus）来完成，匹配工作发生在device_register()和drvier_register()

的时候），probe函数就肯定会被调用，期间一般会完成device的初始化，注册中断等操作。

顺便讲下在内核中是怎么按照driver mode来实现整个系统的设备和驱动注册的。

在系统初始化阶段，会首先向内核注册各种常用的总线类型，比如pci, usb, spi, i2c, platform等等，当然你也可以自己发明一种总线类型注册上去。

这部分代码一般放在./arch/arm/mach-xxx/board-xxx.c中。

在此之后，会将系统的设备列表，基本上整个系统的device都在这里了，一一地注册进内核，就是调用device_regisger注册的过程。然后是对于各个device设备driver的注册。

这部分代码一般放在./drvier/下面。

大部分device和driver的匹配方式就是看名字是否相同，这部分属于总线分内的事情。