Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756537AbbFRTwU (ORCPT ); Thu, 18 Jun 2015 15:52:20 -0400 Received: from mail-yh0-f48.google.com ([209.85.213.48]:35845 "EHLO mail-yh0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751525AbbFRTwM (ORCPT ); Thu, 18 Jun 2015 15:52:12 -0400 MIME-Version: 1.0 In-Reply-To: <20150618180103.GA23809@roeck-us.net> References: <1432342336-25832-1-git-send-email-linux@roeck-us.net> <20150527210447.GY32152@google.com> <20150528022332.GA23724@roeck-us.net> <20150528124112.GJ10210@google.com> <20150618180103.GA23809@roeck-us.net> From: Bjorn Helgaas Date: Thu, 18 Jun 2015 14:51:52 -0500 Message-ID: Subject: Re: [PATCH] PCI: Only enable IO window if supported To: Guenter Roeck Cc: "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Lorenzo Pieralisi , Suravee Suthikulpanit , Will Deacon Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1842 Lines: 40 On Thu, Jun 18, 2015 at 1:01 PM, Guenter Roeck wrote: > On Thu, May 28, 2015 at 07:41:12AM -0500, Bjorn Helgaas wrote: >> >> > > I'd like res->flags to reflect the capabilities of the hardware, not >> > > whether the window is currently enabled. >> > > >> > Flag bits seem to be all taken. Could we use IORESOURCE_DISABLED for that >> > purpose, or could that cause conflicts elsewhere ? >> >> Yes, I think IORESOURCE_DISABLED would be appropriate for any I/O windows >> below a host bridge that doesn't support I/O space. >> > I integrated Lorenzo's patch and tried to get this working. > > Problem is that the use of a resource is widely checked with "!res->flags" > throughout the code. That would have to be changed to something like > "(!res->flags || (res->flags & IORESOURCE_DISABLED))" whereever it is used. > > I tried going with "!res->flags" instead, but have not been able to get it > to work realiably; it is just very difficult to distinguish if "!res->flags" > means that the resource has not yet been assigned or if it means that it is not > supported. > > The correct approach, in my opinion, would be to go with IORESOURCE_DISABLED > and make the necessary changes whereever needed. Effectively this means to > replace the "!res->flags" check with something like pci_res_used() [ pick > your preferred name ] and define it as > > #define pci_res_used(res) ((res)->flags && !((res)->flags & IORESOURCE_DISABLED)) I think that makes sense. Maybe "res_valid()"? It's not really PCI-specific, and "used" is a little ambiguous. So is "valid", I admit. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/