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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 99B9DC433EF for ; Mon, 10 Jan 2022 09:39:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Mime-Version:References:In-Reply-To: Date:Cc:To:From:Subject:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=uQxvWGDqkT1y8nxdFIn3cHlFubrRMjoIQu+A+y1eSGE=; b=Y0BtIHv6Mzf930 yLBLv0U284MKtWBTfZzYNBbMq1lvgagOrQjJfh1nc3ljlvgr2+QoH1OntquGajSbJzDX8Y5G4JBxG Xkp3BFhHY3aHMmiNo+B40wtuLehjHTwq6+zp7CEOv25wLxHcKWDpIb+f33/esZ17fdeXnzg1EeKyK fablSN+K/p2Wb1GI+p/U4EB3dPbWXeYRfcXYGX0HuBpov4+d+hvFG0zdiAsmpelqNEp2pyA2Bkxo8 p36s/jk8JO6JZHwNDVDDLKclPrko0xqfCkPrqTnRr4r84NLzWKkqT+rIzaeat1pjKESkPbjvD/6uu bnM52jdZgGJP3xeE8ALQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1n6r9P-00AUF0-5a; Mon, 10 Jan 2022 09:39:39 +0000 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5] helo=mx0a-001b2d01.pphosted.com) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1n6r4q-00ARHV-NW for linux-riscv@lists.infradead.org; Mon, 10 Jan 2022 09:35:00 +0000 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 20A8SpK3001224; Mon, 10 Jan 2022 09:34:44 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=message-id : subject : from : to : cc : date : in-reply-to : references : content-type : mime-version : content-transfer-encoding; s=pp1; bh=LTgj9BMo0PeVOTmHS425bgS3Erf/sk7QZhpGDMjgyhM=; b=ZeBWbN0MuX3/AcZ5RKWxlntTjtiYf7I8s1BDSqtpXcjWdKYreu00C0yIuS54bslUb+Qr i8eYw95JaW/kRkoSt2zAHTinIjB+A7CPiMdtyB681hPeHcfgnzR85uHf321nrRQFc1lp la9fqV0TOWpjT+vO0xEhhgF1o49lWVqwByJ8qBn2XaRUDR7r5LiwvirD3oVxz1l/G8aA GGCXA11FLJGWT7f5iLejA1BYwhyVqSkuX7XlV9iM6xmQILJKk4eoCpwa9+QQDTpFWY9O RafQfotY4ReY1g/9giu+qtTtTZzWY7egugKozzrEpyohVjle6LQRR+kd516WluIEvvXn Gw== Received: from ppma06fra.de.ibm.com (48.49.7a9f.ip4.static.sl-reverse.com [159.122.73.72]) by mx0b-001b2d01.pphosted.com with ESMTP id 3dfm1hp8jh-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 10 Jan 2022 09:34:44 +0000 Received: from pps.filterd (ppma06fra.de.ibm.com [127.0.0.1]) by ppma06fra.de.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 20A9Rlj5003316; Mon, 10 Jan 2022 09:34:41 GMT Received: from b06cxnps4075.portsmouth.uk.ibm.com (d06relay12.portsmouth.uk.ibm.com [9.149.109.197]) by ppma06fra.de.ibm.com with ESMTP id 3df1vj2baj-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 10 Jan 2022 09:34:41 +0000 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 20A9Ydft44106206 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 10 Jan 2022 09:34:39 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CCEA2A405B; Mon, 10 Jan 2022 09:34:38 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F191AA4065; Mon, 10 Jan 2022 09:34:34 +0000 (GMT) Received: from sig-9-145-16-13.uk.ibm.com (unknown [9.145.16.13]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 10 Jan 2022 09:34:34 +0000 (GMT) Message-ID: <822ad0da702f0953b7aae1febd2c4dfcc4707864.camel@linux.ibm.com> Subject: Re: [RFC 01/32] Kconfig: introduce and depend on LEGACY_PCI From: Niklas Schnelle To: John Garry , Bjorn Helgaas Cc: Mauro Carvalho Chehab , Arnd Bergmann , Hans Verkuil , Ettore Chimenti , Greg Kroah-Hartman , Arnd Bergmann , Bjorn Helgaas , Nick Hu , Greentime Hu , Vincent Chen , Paul Walmsley , Palmer Dabbelt , Albert Ou , Guo Ren , Damien Le Moal , Ian Abbott , H Hartley Sweeten , Linus Walleij , Bartosz Golaszewski , Jean Delvare , Guenter Roeck , Dmitry Torokhov , Karsten Keil , Sathya Prakash , Sreekanth Reddy , Suganath Prabu Subramani , Michael Grzeschik , "David S. Miller" , Jakub Kicinski , Jesse Brandeburg , Tony Nguyen , Kalle Valo , Jouni Malinen , "James E.J. Bottomley" , "Martin K. Petersen" , Hannes Reinecke , Kashyap Desai , Sumit Saxena , Shivasharan S , Nilesh Javali , GR-QLogic-Storage-Upstream@marvell.com, Mark Brown , Sudip Mukherjee , Teddy Wang , Forest Bond , Jiri Slaby , Wim Van Sebroeck , Jaroslav Kysela , Takashi Iwai , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-pci@vger.kernel.org, linux-riscv@lists.infradead.org, linux-csky@vger.kernel.org, linux-ide@vger.kernel.org, linux-gpio@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-i2c@vger.kernel.org, linux-input@vger.kernel.org, netdev@vger.kernel.org, linux-media@vger.kernel.org, MPT-FusionLinux.pdl@broadcom.com, linux-scsi@vger.kernel.org, intel-wired-lan@lists.osuosl.org, linux-wireless@vger.kernel.org, megaraidlinux.pdl@broadcom.com, linux-spi@vger.kernel.org, linux-fbdev@vger.kernel.org, linux-serial@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-watchdog@vger.kernel.org Date: Mon, 10 Jan 2022 10:34:34 +0100 In-Reply-To: <74bf4fde-3972-1c36-ca04-58089da0d82b@huawei.com> References: <20220105194748.GA215560@bhelgaas> <74bf4fde-3972-1c36-ca04-58089da0d82b@huawei.com> X-Mailer: Evolution 3.28.5 (3.28.5-18.el8) Mime-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: RBwht8yqbe4Zp6W3roxBtkr5zQL4IA2M X-Proofpoint-ORIG-GUID: RBwht8yqbe4Zp6W3roxBtkr5zQL4IA2M X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.790,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2022-01-10_04,2022-01-07_01,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 bulkscore=0 impostorscore=0 malwarescore=0 mlxlogscore=999 lowpriorityscore=0 phishscore=0 adultscore=0 spamscore=0 clxscore=1015 mlxscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2110150000 definitions=main-2201100067 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220110_013456_905686_6EEA5614 X-CRM114-Status: GOOD ( 45.30 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Thu, 2022-01-06 at 17:41 +0000, John Garry wrote: > On 05/01/2022 19:47, Bjorn Helgaas wrote: > > > > > > ok if the PCI maintainers decide otherwise. > > > > > I don't really like the "LEGACY_PCI" Kconfig option. "Legacy" just > > > > > means something old and out of favor; it doesn't say*what* that > > > > > something is. > > > > > > > > > > I think you're specifically interested in I/O port space usage, and it > > > > > seems that you want all PCI drivers that*only* use I/O port space to > > > > > depend on LEGACY_PCI? Drivers that can use either I/O or memory > > > > > space or both would not depend on LEGACY_PCI? This seems a little > > > > > murky and error-prone. > > > > I'd like to hear Arnd's opinion on this but you're the PCI maintainer > > > > so of course your buy-in would be quite important for such an option. > > I'd like to hear Arnd's opinion, too. If we do add LEGACY_PCI, I > > think we need a clear guide for when to use it, e.g., "a PCI driver > > that uses inb() must depend on LEGACY_PCI" or whatever it is. > > > > I must be missing something because I don't see what we gain from > > this. We have PCI drivers, e.g., megaraid [1], for devices that have > > either MEM or I/O BARs. I think we want to build drivers like that on > > any arch that supports PCI. > > > > If the arch doesn't support I/O port space, devices that only have I/O > > BARs won't work, of course, and hopefully the PCI core and driver can > > figure that out and gracefully fail the probe. > > > > But that same driver should still work with devices that have MEM > > BARs. If inb() isn't always present, I guess we could litter these > > drivers with #ifdefs, but that would be pretty ugly. I think this is the big question here. If we do go with a compile-time solution as requested by Linus we will either get a lot of #ifdeffery, coarse driver dependencies or as proposed by Alan Stern for the USB #ifdefs might end up turning inb() into a compile-time nop. The originally proposed change that returned ~0 from inb() and printed a warning clearly is the simpler change and sure we could also drop the warning. I'm honestly torn, I do agree with Linus that we shouldn't have run-time things that we know at compile-time will not work but I also dislike all the #ifdeffery a compile-time solution requires. Sadly C really doesn't give us any better tools here. Also I 100% agree with you Bjorn how likely it is to see a device on a platform really shouldn't matter. Without going into details, on s390 we have already beneffited from PCI drivers working with 0 changes to support devices we previously didn't have on the platform or anticipated we would get in the future. Consequently drivers that could work in principle should be built. > > > > There were some ifdefs added to the 8250 drivers in Arnd's original > patch [0], but it does not seem included here. > > Niklas, what happened to the 8250 and the other driver changes? I missed it during the rebase, likely because the changed files compile depend on !S390 via config SERIAL_8250 and thus didn't cause any errors for my allyesconfig. That !S390 dependency is of course not really what we want if the driver can use MEM BARs. _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv