Linux USB内核源码分析(1)

这里是usb初始化时，将usb设备驱动注册到总线上，从usb设备的层次结构(usb device --- configuration --- interface --- point)上来说，这里的driver所对应的为设备描述符(usb device)的驱动. 当然这里的注册过程和usb interface的注册过程类似，只是用的注册函数是 usb_register_driver 而不是usb_register_device_driver。

/* drivers/usb/core/usb.c */
static int __init usb_init(void)
{
  retval = usb_register_device_driver(&usb_generic_driver, THIS_MODULE);
}

/* drivers/usb/core/driver.c */
int usb_register_device_driver(struct usb_device_driver *new_udriver,
                               struct module *owner)
{
  new_udriver->drvwrap.driver.bus = &usb_bus_type;
  retval = driver_register(&new_udriver->drvwrap.driver);
}

/* drivers/base/driver.c */
int driver_register(struct device_driver *drv)
{
  ret = bus_add_driver(drv);
}

/* drivers/base/bus.c */
int bus_add_driver(struct device_driver *drv)
{
  bus = bus_get(drv->bus);
  priv = kzalloc(sizeof(*priv), GFP_KERNEL);
  priv->driver = drv;
  drv->p = priv;
  klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
}

下面我们看一看usb_generic_driver里的函数，我们仅看下probe的这条线

/* drivers/usb/core/generic.c */
static int generic_probe(struct usb_device *udev)
{
  c = usb_choose_configuration(udev);
  if (c >= 0) { 
    err = usb_set_configuration(udev, c);
  }
}

/* drivers/usb/core/message.c */
int usb_set_configuration(struct usb_device *dev, int configuration)
{
  for (i = 0; i < nintf; ++i) {
    ret = device_add(&intf->dev);
    create_intf_ep_devs(intf);
  }
}

/* drivers/base/core.c */
int device_add(struct device *dev)
{
  bus_probe_device(dev);
}

/* drivers/base/bus.c */
void bus_probe_device(struct device *dev)
{
  if (bus && bus->p->drivers_autoprobe) {
    ret = device_attach(dev);
  }
}

/* drivers/base/dd.c */
int device_attach(struct device *dev) 
{
  if (dev->driver) {
    ret = device_bind_driver(dev); 
  } else {
    ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach); 
  }
}

int bus_for_each_drv(struct bus_type *bus, struct device_driver *start,
                     void *data, int (*fn)(struct device_driver *, void *))
{
  /* 遍历所有驱动 */
  klist_iter_init_node(&bus->p->klist_drivers, &i,
                     	start ? &start->p->knode_bus : NULL);
  while ((drv = next_driver(&i)) && !error)
    error = fn(drv, data);
}

static int __device_attach(struct device_driver *drv, void *data)
{
  /* 这里进行匹配ID，如果有支持的驱动，执行probe函数 */
  if (!driver_match_device(drv, dev))
    retrun 0;

  return driver_probe_device(drv, dev);
}

int driver_probe_device(struct device_driver *drv, struct device *dev)
{
  ret = really_probe(dev, drv); 
}

static int really_probe(struct device *dev, struct device_driver *drv)
{
  if (dev->bus->probe) {
    ret = dev->bus->probe(dev);
  } else if (drv->probe) {
    ret = drv->probe(dev);
  }
}