Linux Kernel设备驱动模型之class 查找设备

/**  * class_find_device - device iterator for locating a particular device  * @class: the class we're iterating  * @start: Device to begin with  * @data: data for the match function  * @match: function to check device  *  * This is similar to the class_for_each_dev() function above, but it  * returns a reference to a device that is 'found' for later use, as  * determined by the @match callback.  *  * The callback should return 0 if the device doesn't match and non-zero  * if it does.  If the callback returns non-zero, this function will  * return to the caller and not iterate over any more devices.  *  * Note, you will need to drop the reference with put_device() after use.  *  * @match is allowed to do anything including calling back into class  * code.  There's no locking restriction.  */ struct device *class_find_device(struct class *class, struct device *start,      const void *data,      int (*match)(struct device *, const void *)) {  struct class_dev_iter iter;  struct device *dev;

 if (!class)   return NULL;  if (!class->p) {   WARN(1, "%s called for class '%s' before it was initialized",        __func__, class->name);   return NULL;  }

 class_dev_iter_init(&iter, class, start, NULL);  while ((dev = class_dev_iter_next(&iter))) {   if (match(dev, data)) {    get_device(dev);    break;   }  }  class_dev_iter_exit(&iter);

 return dev; }