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 A70B8C28CF5 for ; Tue, 28 Dec 2021 12:54:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231918AbhL1Myw (ORCPT ); Tue, 28 Dec 2021 07:54:52 -0500 Received: from ams.source.kernel.org ([145.40.68.75]:45878 "EHLO ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231695AbhL1Myr (ORCPT ); Tue, 28 Dec 2021 07:54:47 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 55AA6B811D9; Tue, 28 Dec 2021 12:54:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4546BC36AE8; Tue, 28 Dec 2021 12:54:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1640696083; bh=Gap0GwZ7QhskHCBuxCWJ0ehIbXdcDMw/3DRBfuFroAo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=uT1Bi526RdiqCovjK+BsZ0LQ21O6eAGdLfperJgxt/T4KZXCQHLowjI+U/BnL+30l HJRegFW6ceEx7gRTUzAnY/lOi8+345syFMoVZJg23IyMTVv8lxOmatGJsejunnysTY b7cgtAhK1rV1ciaHNDicksS8OtcQVVqsJ8fTaLs35K3JpOGyDL1M7tu/pQlaK0TC5o 847l3oZwcFMOo4LfbX6OTisn674FFeznktD1n6AMeVW9VoFWIsJndv9O02I/tcIR5D xfPFEZmvAPeSdi4V+6+pSCDV5v0lZDnuzytqnQmuAjGw0iIL513WDap3bYMORE0U6k 6wPKV3GCt3SBA== Date: Tue, 28 Dec 2021 13:54:25 +0100 From: Mauro Carvalho Chehab To: Niklas Schnelle Cc: Greg Kroah-Hartman , Arnd Bergmann , Bjorn Helgaas , John Garry , 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 , Hans Verkuil , 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-staging@lists.linux.dev, linux-serial@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-watchdog@vger.kernel.org, alsa-devel@alsa-project.org Subject: Re: [RFC 01/32] Kconfig: introduce and depend on LEGACY_PCI Message-ID: <20211228135425.0a69168c@coco.lan> In-Reply-To: References: <20211227164317.4146918-1-schnelle@linux.ibm.com> <20211227164317.4146918-2-schnelle@linux.ibm.com> <20211228101435.3a55b983@coco.lan> X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.30; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org Em Tue, 28 Dec 2021 11:58:55 +0100 Niklas Schnelle escreveu: > On Tue, 2021-12-28 at 10:15 +0100, Mauro Carvalho Chehab wrote: > > Em Tue, 28 Dec 2021 09:21:23 +0100 > > Greg Kroah-Hartman escreveu: > > > > > On Mon, Dec 27, 2021 at 05:42:46PM +0100, Niklas Schnelle wrote: > > > > --- a/drivers/pci/Kconfig > > > > +++ b/drivers/pci/Kconfig > > > > @@ -23,6 +23,17 @@ menuconfig PCI > > > > > > > > if PCI > > > > > > > > +config LEGACY_PCI > > > > + bool "Enable support for legacy PCI devices" > > > > + depends on HAVE_PCI > > > > + help > > > > + This option enables support for legacy PCI devices. This includes > > > > + PCI devices attached directly or via a bridge on a PCI Express bus. > > > > + It also includes compatibility features on PCI Express devices which > > > > + make use of legacy I/O spaces. > > > > This Kconfig doesn't seem what it is needed there, as this should be an > > arch-dependent feature, and not something that the poor user should be > > aware if a given architecture supports it or not. Also, the above will keep > > causing warnings or errors with randconfigs. > > > > Also, the "depends on HAVE_CPI" is bogus, as PCI already depends on > > HAVE_PCI: > > Ah yes you're right. > > > > > menuconfig PCI > > bool "PCI support" > > depends on HAVE_PCI > > help > > This option enables support for the PCI local bus, including > > support for PCI-X and the foundations for PCI Express support. > > Say 'Y' here unless you know what you are doing. > > > > So, instead, I would expect that a new HAVE_xxx option would be > > added at arch/*/Kconfig, like: > > > > config X86 > > ... > > select HAVE_PCI_DIRECT_IO > > > > It would also make sense to document it at Documentation/features/. > > I'll look into that, thanks. > > > > > > All you really care about is the "legacy" I/O spaces here, this isn't > > > tied to PCI specifically at all, right? > > > > > > So why not just have a OLD_STYLE_IO config option or something like > > > that, to show that it's the i/o functions we care about here, not PCI at > > > all? > > > > > > And maybe not call it "old" or "legacy" as time constantly goes forward, > > > just describe it as it is, "DIRECT_IO"? > > > > Agreed. HAVE_PCI_DIRECT_IO (or something similar) seems a more appropriate > > name for it. > > > > Thanks, > > Mauro > > Hmm, I might be missing something here but that sounds a lot like the > HAS_IOPORT option added in patch 02. > > We add both LEGACY_PCI and HAS_IOPORT to differentiate between two > cases. HAS_IOPORT is for PC-style devices that are not on a PCI card > while LEGACY_PCI is for PCI drivers that require port I/O. I didn't look at the other patches on this series, but why it is needed to deal with them on a separate way? Won't "PCI" and "HAS_IOPORT" be enough? I mean, are there any architecture where HAVE_PCI=y and HAS_IOPORT=y where LEGACY_PCI shall be "n"? > This > includes pre-PCIe devices as well as PCIe devices which require > features like I/O spaces. The "legacy" naming is comes from the PCIe > spec which in section 2.1.1.2 says "PCI Express supports I/O Space for > compatibility with legacy devices which require their use. Future > revisions of this specification may deprecate the use of I/O Space." I would still avoid calling it LEGACY_PCI, as this sounds too generic. I didn't read the PCI/PCIe specs, but I suspect that are a lot more features that were/will be deprecated on PCI specs as time goes by. So, I would, instead, use something like PCI_LEGACY_IO_SPACE or HAVE_PCI_LEGACY_IO_SPACE, in order to let it clear what "legacy" means. > These two separate config options allow us to compile without support > for these legacy PCI devices even on a system where inb()/outb() and > friends are required for some PC style devices and for example ACPI. Hmm... why this patch make SND_BT87X dependent on LEGACY_PCI? > @@ -172,6 +177,7 @@ config SND_AZT3328 > > config SND_BT87X > tristate "Bt87x Audio Capture" > + depends on LEGACY_PCI > select SND_PCM > help > If you want to record audio from TV cards based on I couldn't find any usage of inb/outb & friends on it: $ grep -E '(inb|outb|inw|outw|inl|outl)\b' ./sound/pci/bt87x.c It uses, instead, readl/writel: static inline u32 snd_bt87x_readl(struct snd_bt87x *chip, u32 reg) { return readl(chip->mmio + reg); } static inline void snd_bt87x_writel(struct snd_bt87x *chip, u32 reg, u32 value) { writel(value, chip->mmio + reg); } I failed to see what makes it different from VIDEO_BT848 and DVB_BT8XX drivers. They all support exactly the same chipset: Brooktree/Conexant BT8xx. On those devices, depending on the exact model, up to three separate interfaces are provided, each one with its own Kconfig var: - audio I/O (SND_BT87X); - video I/O (VIDEO_BT848); - MPEG-TS I/O (DVB_BT8XX). Thanks, Mauro