From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: [patch 2/2] PNP: don't check disabled PCI BARs for conflicts in quirk_system_pci_resources() Date: Mon, 29 Sep 2008 09:34:54 -0700 (PDT) Message-ID: References: <200809290953.56565.bjorn.helgaas@hp.com> <200809290957.59813.bjorn.helgaas@hp.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:51604 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751293AbYI2QgV (ORCPT ); Mon, 29 Sep 2008 12:36:21 -0400 In-Reply-To: <200809290957.59813.bjorn.helgaas@hp.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Bjorn Helgaas Cc: Jesse Barnes , Len Brown , Frans Pop , Rene Herman , "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-acpi@vger.kernel.org, Adam Belay , Avuton Olrich , Karl Bellve , Willem Riede , Matthew Hall On Mon, 29 Sep 2008, Bjorn Helgaas wrote: > > + if (!pci_resource_enabled(pdev, i)) > + continue; I really don't think this is the right approach. Maybe the PCI device has been turned off, but the *resource* may still be valid. Wouldn't it be much better to just check whether the resource is inserted in the resource tree or not? Quite frankly, it looks like your change will basically cause us to look over *every* system PnP resource, and for each of them, it will look at *every* PCI device, and for each PCI device it will look at *every* BAR, and for each BAR it finds it will read the PCI status register, over and over and over again. Now, I doubt you'll be able to wear out the PCI bus, but doesn't this just make you go "umm, that's not pretty, and it doesn't make much sense". If we've detected the PCI resource as being valid by the PCI layer, why not just use that information? And afaik, the easy way to check that is just whether it's inserted into the resource tree, which in turn is most trivially done by just checking whether the resource has a parent. IOW, why isn't it just doing struct resource *res = dev->resource[bar]; if (!res->parent) continue; or something? Or what was wrong with just checking the res->start for being zero? Wherever PnP is relevant, resources that start at zero are disabled, no? Linus