platfrom的probe的详解

probe()函数是什么时候被调用,设备和驱动是怎么联系起来的

平台设备的注册

platform_add_devices(ldd6410_devices, ARRAY_SIZE(ldd6410_devices));  //这是bsp中添加所有的设备

--> 

platform_device_register(devs[i]);//注册平台设备

--->

platform_device_add(pdev);将平台设备加入到platform_bus中

--->

device_add(&pdev->dev);

 

平台驱动的注册

platform_driver_register(&gpio_led_driver)

---->

driver_register(&drv->driver);

---->

bus_add_driver(drv); //添加驱动到总线

--->

driver_attach(drv);//为驱动寻找相应的设备

---->

__driver_attach()

---->

driver_probe_device(drv, dev); 

--->

really_probe(dev, drv);

 

static int __init XXX_init(void)
{
 return platform_driver_register(&XXX_driver);   //注册平台驱动
}

int driver_attach(struct device_driver *drv)
{
 return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);   //遍历设备总线寻找驱动
}

static int __driver_attach(struct device *dev, void *data)
{
 struct device_driver *drv = data;

 /*
  * Lock device and try to bind to it. We drop the error
  * here and always return 0, because we need to keep trying
  * to bind to devices and some drivers will return an error
  * simply if it didn't support the device.
  *
  * driver_probe_device() will spit a warning if there 
  * is an error.
  */

 if (drv->bus->match && !drv->bus->match(dev, drv))   //通过match判断驱动和设备是否匹配，这里通过比较dev和drv中的设备名来判断，所以设备名需要唯一
  return 0;

 if (dev->parent) /* Needed for USB */
  down(&dev->parent->sem);
 down(&dev->sem);
 if (!dev->driver)
  driver_probe_device(drv, dev);  //   驱动和设备绑定
 up(&dev->sem);
 if (dev->parent)
  up(&dev->parent->sem);

 return 0;
}

 
static int really_probe(struct device *dev, struct device_driver *drv)
{
 int ret = 0;

 atomic_inc(&probe_count);
 pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
   drv->bus->name, __func__, drv->name, dev->bus_id);
 WARN_ON(!list_empty(&dev->devres_head));

 dev->driver = drv;
 if (driver_sysfs_add(dev)) {
  printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
   __func__, dev->bus_id);
  goto probe_failed;
 }

 if (dev->bus->probe) {   
  ret = dev->bus->probe(dev);
  if (ret)
   goto probe_failed;
 } else if (drv->probe) {
  ret = drv->probe(dev);  //这里才真正调用了驱动的probe
  if (ret)
   goto probe_failed;
 }

 driver_bound(dev);
 ret = 1;
 pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
   drv->bus->name, __func__, dev->bus_id, drv->name);
 goto done;

probe_failed:
 devres_release_all(dev);
 driver_sysfs_remove(dev);
 dev->driver = NULL;

 if (ret != -ENODEV && ret != -ENXIO) {
  /* driver matched but the probe failed */
  printk(KERN_WARNING
         "%s: probe of %s failed with error %d\n",
         drv->name, dev->bus_id, ret);
 }
 /*
  * Ignore errors returned by ->probe so that the next driver can try
  * its luck.
  */
 ret = 0;
done:
 atomic_dec(&probe_count);
 wake_up(&probe_waitqueue);
 return ret;
}