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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 F08ECC433DB for ; Thu, 25 Mar 2021 14:41:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF82761A2F for ; Thu, 25 Mar 2021 14:41:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230476AbhCYOlc (ORCPT ); Thu, 25 Mar 2021 10:41:32 -0400 Received: from netrider.rowland.org ([192.131.102.5]:36153 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S231270AbhCYOlK (ORCPT ); Thu, 25 Mar 2021 10:41:10 -0400 Received: (qmail 788698 invoked by uid 1000); 25 Mar 2021 10:41:09 -0400 Date: Thu, 25 Mar 2021 10:41:09 -0400 From: Alan Stern To: Heikki Krogerus Cc: Greg Kroah-Hartman , Benson Leung , Prashant Malani , Guenter Roeck , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/6] usb: Iterator for ports Message-ID: <20210325144109.GB785961@rowland.harvard.edu> References: <20210325122926.58392-1-heikki.krogerus@linux.intel.com> <20210325122926.58392-2-heikki.krogerus@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210325122926.58392-2-heikki.krogerus@linux.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 25, 2021 at 03:29:21PM +0300, Heikki Krogerus wrote: > Introducing usb_for_each_port(). It works the same way as > usb_for_each_dev(), but instead of going through every USB > device in the system, it walks through the USB ports in the > system. > > Signed-off-by: Heikki Krogerus This has a couple of nasty errors. > --- > drivers/usb/core/usb.c | 43 ++++++++++++++++++++++++++++++++++++++++++ > include/linux/usb.h | 1 + > 2 files changed, 44 insertions(+) > > diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c > index 2ce3667ec6fae..6d49db9a1b208 100644 > --- a/drivers/usb/core/usb.c > +++ b/drivers/usb/core/usb.c > @@ -398,6 +398,49 @@ int usb_for_each_dev(void *data, int (*fn)(struct usb_device *, void *)) > } > EXPORT_SYMBOL_GPL(usb_for_each_dev); > > +struct each_hub_arg { > + void *data; > + int (*fn)(struct device *, void *); > +}; > + > +static int __each_hub(struct device *dev, void *data) > +{ > + struct each_hub_arg *arg = (struct each_hub_arg *)data; > + struct usb_device *hdev = to_usb_device(dev); to_usb_device() won't work properly if the struct device isn't embedded in an actual usb_device structure. And that will happen, since the USB bus type holds usb_interface structures as well as usb_devices. In fact, you should use usb_for_each_dev here; it already does what you want. > + struct usb_hub *hub; > + int ret; > + int i; > + > + hub = usb_hub_to_struct_hub(hdev); > + if (!hub) > + return 0; > + > + for (i = 0; i < hdev->maxchild; i++) { > + ret = arg->fn(&hub->ports[i]->dev, arg->data); > + if (ret) > + return ret; > + } > + > + return 0; > +} Don't you need some sort of locking or refcounting here? What would happen if this hub got removed while the routine was running? Alan Stern