From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9CDBBC433ED for ; Fri, 16 Apr 2021 15:21:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7BAE9611AF for ; Fri, 16 Apr 2021 15:21:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343587AbhDPPVz (ORCPT ); Fri, 16 Apr 2021 11:21:55 -0400 Received: from netrider.rowland.org ([192.131.102.5]:48199 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S245435AbhDPPUs (ORCPT ); Fri, 16 Apr 2021 11:20:48 -0400 Received: (qmail 43577 invoked by uid 1000); 16 Apr 2021 11:20:21 -0400 Date: Fri, 16 Apr 2021 11:20:21 -0400 From: Alan Stern To: liulongfang Cc: gregkh@linuxfoundation.org, mathias.nyman@intel.com, liudongdong3@huawei.com, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, kong.kongxinwei@hisilicon.com, yisen.zhuang@huawei.com Subject: Re: [RFC PATCH] USB:XHCI:skip hub registration Message-ID: <20210416152021.GA42403@rowland.harvard.edu> References: <1618489358-42283-1-git-send-email-liulongfang@huawei.com> <20210415144323.GC1530055@rowland.harvard.edu> <3dad6f4f-6386-427c-c36c-7d26b9a76fa4@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3dad6f4f-6386-427c-c36c-7d26b9a76fa4@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 16, 2021 at 10:03:21AM +0800, liulongfang wrote: > On 2021/4/15 22:43, Alan Stern wrote: > > On Thu, Apr 15, 2021 at 08:22:38PM +0800, Longfang Liu wrote: > >> When the number of ports on the USB hub is 0, skip the registration > >> operation of the USB hub. > >> > >> The current Kunpeng930's XHCI hardware controller is defective. The number > >> of ports on its USB3.0 bus controller is 0, and the number of ports on > >> the USB2.0 bus controller is 1. > >> > >> In order to solve this problem that the USB3.0 controller does not have > >> a port which causes the registration of the hub to fail, this patch passes > >> the defect information by adding flags in the quirks of xhci and usb_hcd, > >> and finally skips the registration process of the hub directly according > >> to the results of these flags when the hub is initialized. > >> > >> Signed-off-by: Longfang Liu > > > > The objections that Greg raised are all good ones. > > > > But even aside from them, this patch doesn't actually do what the > > description says. The patch doesn't remove the call to usb_add_hcd > > for the USB-3 bus. If you simply skipped that call (and the > > corresponding call to usb_remove_hcd) when there are no > > ports on the root hub, none of the stuff in this patch would be needed. > > > > Alan Stern > > > > "[RFC PATCH] USB:XHCI:Adjust the log level of hub" I don't understand. What patch is that? Do you have a URL for it? > The current method is an improved method of the above patch. > This patch just make it skip registering USB-3 root hub if that hub has no ports, No, that isn't what this patch does. If the root hub wasn't registered, hub_probe wouldn't get called. But with your patch, the system tries to register the root hub, and it does call hub_probe, and then that function fails with a warning message. The way to _really_ akip registering the root hub is to change the xhci-hcd code. Make it skip calling usb_add_hcd. > after skipping registering, no port will not report error log,the goal of this > patch is reached without error log output. Why do you want to get rid of the error log output? There really _is_ an error, because the USB-3 hardware on your controller is defective. Since the hardware is buggy, we _should_ print an error message in the kernel log. Alan Stern