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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 0E868C433C1 for ; Thu, 25 Mar 2021 15:21:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D3AA461A1D for ; Thu, 25 Mar 2021 15:21:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231384AbhCYPUu (ORCPT ); Thu, 25 Mar 2021 11:20:50 -0400 Received: from mail.kernel.org ([198.145.29.99]:36788 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231437AbhCYPUS (ORCPT ); Thu, 25 Mar 2021 11:20:18 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id ECEE961A17; Thu, 25 Mar 2021 15:20:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1616685618; bh=I2CXsEYjwlZ/FRznJeRrrqBihn6wC60KAXqXZjW+CQc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=q9SEECshckRBCqciAvQONmiPmwDYmNxtp1Gx/v7MKR2NlYeQmLGE4Ha8AIsZS59v6 CR+4onPzDuEzXW3TfNRUM9Q+rglnZXfOrZy/LF7LJGJZg140129c7UCmvYBbrjJidP EFDtC+QjZAaUwL7wNLMvlXubqND6QBTxJknDyf3I= Date: Thu, 25 Mar 2021 16:20:15 +0100 From: Greg Kroah-Hartman To: Heikki Krogerus Cc: Alan Stern , 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: References: <20210325122926.58392-1-heikki.krogerus@linux.intel.com> <20210325122926.58392-2-heikki.krogerus@linux.intel.com> <20210325144109.GB785961@rowland.harvard.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 25, 2021 at 05:14:42PM +0200, Heikki Krogerus wrote: > On Thu, Mar 25, 2021 at 10:41:09AM -0400, Alan Stern wrote: > > 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. > > OK, so I need to filter them out. > > > In fact, you should use usb_for_each_dev here; it already does what you > > want. > > Unfortunately I can't use usb_for_each_dev here, because it deals with > struct usb_device while I need to deal with struct device in the > callback. Why do you need 'struct device' in the callback? All you really want is the hub devices, right? > > > + 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? > > I'll use a lock then. That's not going to work to be held over a callback. Just properly increment the reference count. thanks, greg k-h