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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 7CC4FC433DF for ; Wed, 1 Jul 2020 12:47:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 582BA20775 for ; Wed, 1 Jul 2020 12:47:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730603AbgGAMrJ (ORCPT ); Wed, 1 Jul 2020 08:47:09 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:7329 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730388AbgGAMrI (ORCPT ); Wed, 1 Jul 2020 08:47:08 -0400 Received: from DGGEMS406-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 4AB88B12259715F874FE; Wed, 1 Jul 2020 20:47:06 +0800 (CST) Received: from [10.65.58.147] (10.65.58.147) by DGGEMS406-HUB.china.huawei.com (10.3.19.206) with Microsoft SMTP Server id 14.3.487.0; Wed, 1 Jul 2020 20:47:02 +0800 Subject: Re: [PATCH] PCI: Make pcie_find_root_port() work for PCIe root ports as well To: Mika Westerberg References: <20200630220107.GA3489322@bjorn-Precision-5520> <20200701101541.GO5180@lahna.fi.intel.com> CC: Bjorn Helgaas , Bjorn Helgaas , Kalle Valo , From: Yicong Yang Message-ID: <0e6f9741-03a2-816e-d288-f9532b6d0a26@hisilicon.com> Date: Wed, 1 Jul 2020 20:47:10 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <20200701101541.GO5180@lahna.fi.intel.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.65.58.147] X-CFilter-Loop: Reflected Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On 2020/7/1 18:15, Mika Westerberg wrote: > On Wed, Jul 01, 2020 at 09:53:51AM +0800, Yicong Yang wrote: >>> static inline struct pci_dev *pcie_find_root_port(struct pci_dev *dev) >>> { >>> - struct pci_dev *bridge = pci_upstream_bridge(dev); >>> - >>> - while (bridge) { >>> - if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT) >>> - return bridge; >>> - bridge = pci_upstream_bridge(bridge); >>> + while (dev) { >>> + if (pci_is_pcie(dev) && >>> + pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT) >>> + return dev; >>> + dev = pci_upstream_bridge(dev); >>> } >>> >> We may have some problems here, as after pcie_find_root_port() called, *dev will >> be either root port or NULL but users may want it unchanged. One such usage is >> in acpi_pci_bridge_d3(), drivers/pci/pci-acpi.c, *dev is used as origin >> after called this. >> >> So we should use a temporary point to *dev rather than directly modify it. > dev is already a copy of what is passed by the caller so it does not > matter if it gets changed here. You would need to pass it through struct > pci_dev **dev in order to modify the passed pointer. Ah...I must be fuzzy in mind then. Thanks. > . >