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=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 78636C433EB for ; Sun, 2 Aug 2020 18:47:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5B1A820738 for ; Sun, 2 Aug 2020 18:47:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="km2ppJ9W" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726985AbgHBSrY (ORCPT ); Sun, 2 Aug 2020 14:47:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49026 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725801AbgHBSrW (ORCPT ); Sun, 2 Aug 2020 14:47:22 -0400 Received: from mail.skyhub.de (mail.skyhub.de [IPv6:2a01:4f8:190:11c2::b:1457]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 90B30C06174A; Sun, 2 Aug 2020 11:47:22 -0700 (PDT) Received: from nazgul.tnic (unknown [78.130.214.198]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 6060E1EC027B; Sun, 2 Aug 2020 20:47:20 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1596394040; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=6tNJPljLjNx2x9QEIVJnns37NMBlLLp4EAbpTzGkx/k=; b=km2ppJ9W1lKPkeogNByCZRPPB90pQ77y1xFpzqsz5v2Gw4jUrJuG2BUGC6FlwifBWKp5xA i/pwFuidiFCe1IAhyK7PX67NxCd1gqUPGlQREtpW/WPoHky93LT53Q3Zqf5RRY0CErhAu0 8YCnO7sm9NOsIwnrSCtwGhnf6GzAdAw= Date: Sun, 2 Aug 2020 20:46:48 +0200 From: Borislav Petkov To: Saheed Bolarinwa Cc: trix@redhat.com, helgaas@kernel.org, Kalle Valo , "David S. Miller" , Jakub Kicinski , Wolfgang Grandegger , Marc Kleine-Budde , Miquel Raynal , Richard Weinberger , Vignesh Raghavendra , Joerg Roedel , bjorn@helgaas.com, skhan@linuxfoundation.org, linux-kernel-mentees@lists.linuxfoundation.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-mtd@lists.infradead.org, iommu@lists.linux-foundation.org, linux-rdma@vger.kernel.org, linux-ide@vger.kernel.org, linux-i2c@vger.kernel.org, linux-hwmon@vger.kernel.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-gpio@vger.kernel.org, linux-fpga@vger.kernel.org, linux-edac@vger.kernel.org, dmaengine@vger.kernel.org, linux-crypto@vger.kernel.org, linux-atm-general@lists.sourceforge.net Subject: Re: [RFC PATCH 00/17] Drop uses of pci_read_config_*() return value Message-ID: <20200802184648.GA23190@nazgul.tnic> References: <20200801112446.149549-1-refactormyself@gmail.com> <20200801125657.GA25391@nazgul.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Sun, Aug 02, 2020 at 07:28:00PM +0200, Saheed Bolarinwa wrote: > Because the value ~0 has a meaning to some drivers and only No, ~0 means that the PCI read failed. For *every* PCI device I know. Here's me reading from 0xf0 offset of my hostbridge: # setpci -s 00:00.0 0xf0.l 01000000 That device doesn't have extended config space, so the last valid byte is 0xff. Let's read beyond that: # setpci -s 00:00.0 0x100.l ffffffff > Again, only the drivers can determine if ~0 is a valid value. This > information is not available inside pci_config_read*(). Of course it is. *every* change you've done in 6/17 - this is the only patch I have received - checks for == ~0. So that check can just as well be moved inside pci_config_read_*(). Here's how one could do it: #define PCI_OP_READ(size, type, len) \ int noinline pci_bus_read_config_##size \ (struct pci_bus *bus, unsigned int devfn, int pos, type *value) \ { \ int res; \ unsigned long flags; \ u32 data = 0; \ if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER; \ pci_lock_config(flags); \ res = bus->ops->read(bus, devfn, pos, len, &data); \ /* Check we actually read something which is not all 1s.*/ if (data == ~0) return PCIBIOS_READ_FAILED; *value = (type)data; \ pci_unlock_config(flags); \ return res; \ } Also, I'd prefer a function to *not* return void but return either an error or success. In the success case, the @value argument can be consumed by the caller and otherwise not. In any case, that change is a step in the wrong direction and I don't like it, sorry. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette