USB core(一) - rh_queue_status与rh_call_control

rh_call_control

为了说明rh_call_control，先来看看是如何通过usb_control_msg，接着usb_submit_urb，然后rh_urb_enqueue，最终在调用rh_call_control的过程。

hub信息获取函数

get_hub_descriptor(struct usb_device *hdev, void *data)
    usb_control_msg(hdev, usb_rcvctrlpipe(hdev, 0),
                        USB_REQ_GET_DESCRIPTOR, USB_DIR_IN | USB_RT_HUB,
                        dtype << 8, 0, data, size,
                        USB_CTRL_GET_TIMEOUT);

clear_hub_feature(struct usb_device *hdev, int feature)
    usb_control_msg(hdev, usb_sndctrlpipe(hdev, 0),
                USB_REQ_CLEAR_FEATURE, usb_control_msg, featur