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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57203E92FC9 for ; Thu, 5 Oct 2023 22:51:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231766AbjJEWvK (ORCPT ); Thu, 5 Oct 2023 18:51:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46826 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229527AbjJEWvJ (ORCPT ); Thu, 5 Oct 2023 18:51:09 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A92D5DE; Thu, 5 Oct 2023 15:51:03 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0C844C433C7; Thu, 5 Oct 2023 22:51:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1696546263; bh=6Z+aNRTykgUl2shYjBKN3j99iPvZlR6BDg/SD2cELU8=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=MNukphMSInGVUe6e01X0aki2ed92AZyanoAXS1Tse2jkA9W3Ip2Vrq3qZXUuWFeAm 5THAUEv1ZFV7lRkX73pa5wFZbrMZVnBtOOADNoSVhDoSwvQbgRCf2ReCyg2FU8JDiw hJBi1H9FhrZ6OnSz/lmhK+ZlshRSG+Z1VQ5zHtoIInARuChulTjTyRksLL+HT8wYwb /b2wAQVwnnFrh5H08XEA415LtQagTLgi6HT7mMLSLLrpdJGnm+chWdfYEO2Pvwz94V kz4ubbn+i563g6Wk23YSZYGgBg7iCQAhlJKyFUj281GiAyrIznmNiSXnDuSpnsUr5o bPn9QBR7/7oXQ== Date: Thu, 5 Oct 2023 17:51:01 -0500 From: Bjorn Helgaas To: Sui Jingfeng Cc: Bjorn Helgaas , Gerd Hoffmann , Gurchetan Singh , Chia-I Wu , Sui Jingfeng , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, virtualization@lists.linux-foundation.org, "Maciej W. Rozycki" Subject: Re: [-next 1/5] PCI: Add the pci_is_vga() helper Message-ID: <20231005225101.GA792747@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230830111532.444535-2-sui.jingfeng@linux.dev> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Wed, Aug 30, 2023 at 07:15:28PM +0800, Sui Jingfeng wrote: > From: Sui Jingfeng > > The PCI code and ID assignment specification defined four types of > display controllers for the display base class(03h), and the devices > with 0x00h sub-class code are VGA devices. VGA devices with programming I can update this with the spec details (PCI Code and Assignment spec r1.15, secs 1.1 and 1.4). > interface 0x00 is VGA-compatible, VGA devices with programming interface > 0x01 are 8514-compatible controllers. Besides, PCI_CLASS_NOT_DEFINED_VGA > is defined to provide backward compatibility for devices that were built > before the class code field was defined. Hence, introduce the pci_is_vga() > helper, let it handle the details for us. It returns true if the PCI(e) > device being tested belongs to the VGA devices category. > > Cc: "Maciej W. Rozycki" > Signed-off-by: Sui Jingfeng > --- > include/linux/pci.h | 27 +++++++++++++++++++++++++++ > 1 file changed, 27 insertions(+) > > diff --git a/include/linux/pci.h b/include/linux/pci.h > index cf6e0b057752..ace727001911 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -713,6 +713,33 @@ static inline bool pci_is_bridge(struct pci_dev *dev) > dev->hdr_type == PCI_HEADER_TYPE_CARDBUS; > } > > +/** > + * The PCI code and ID assignment specification defined four types of > + * display controllers for the display base class(03h), and the devices > + * with 0x00h sub-class code are VGA devices. VGA devices with programming > + * interface 0x00 is VGA-compatible, VGA devices with programming interface > + * 0x01 are 8514-compatible controllers. Besides, PCI_CLASS_NOT_DEFINED_VGA > + * is defined to provide backward compatibility for devices that were built > + * before the class code field was defined. This means that it belong to the > + * VGA devices category also. > + * > + * Returns: > + * true if the PCI device is a VGA device, false otherwise. > + */ > +static inline bool pci_is_vga(struct pci_dev *pdev) > +{ > + if (!pdev) > + return false; > + > + if ((pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA) > + return true; > + > + if ((pdev->class >> 8) == PCI_CLASS_NOT_DEFINED_VGA) > + return true; Are you seeing a problem that will be fixed by this series, i.e., a PCI_CLASS_NOT_DEFINED_VGA device that we currently don't handle correctly? I think this makes sense per the spec, but there's always a risk of breaking something, so it's nice if the change actually *fixes* something to make that risk worthwhile. > + return false; > +} > + > #define for_each_pci_bridge(dev, bus) \ > list_for_each_entry(dev, &bus->devices, bus_list) \ > if (!pci_is_bridge(dev)) {} else > -- > 2.34.1 >