From mboxrd@z Thu Jan 1 00:00:00 1970 From: Randy Dunlap Subject: Re: [PATCH v10 3/7] PCI: reserve bus range for SR-IOV device Date: Mon, 09 Mar 2009 11:09:02 -0700 Message-ID: <49B55B3E.3090502@oracle.com> References: <1235112888-9524-1-git-send-email-yu.zhao@intel.com> <1235112888-9524-4-git-send-email-yu.zhao@intel.com> <20090306202024.GF25995@parisc-linux.org> <20090309081337.GB4638@yzhao-otc.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Matthew Wilcox , "jbarnes@virtuousgeek.org" , "linux-pci@vger.kernel.org" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" To: Yu Zhao Return-path: Received: from rcsinet13.oracle.com ([148.87.113.125]:57389 "EHLO rgminet13.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751271AbZCISHV (ORCPT ); Mon, 9 Mar 2009 14:07:21 -0400 In-Reply-To: <20090309081337.GB4638@yzhao-otc.sh.intel.com> Sender: kvm-owner@vger.kernel.org List-ID: Yu Zhao wrote: > On Sat, Mar 07, 2009 at 04:20:24AM +0800, Matthew Wilcox wrote: >> On Fri, Feb 20, 2009 at 02:54:44PM +0800, Yu Zhao wrote: >>> +static inline void virtfn_bdf(struct pci_dev *dev, int id, u8 *busnr, u8 *devfn) >>> +{ >>> + u16 bdf; >>> + >>> + bdf = (dev->bus->number << 8) + dev->devfn + >>> + dev->sriov->offset + dev->sriov->stride * id; >>> + *busnr = bdf >> 8; >>> + *devfn = bdf & 0xff; >>> +} >> I find the interface here a bit clunky -- a function returning void >> while having two OUT parameters. How about this variation on the theme >> (viewers are encouraged to come up with their own preferred >> implementations and interfaces): >> >> static inline __pure u16 virtfn_bdf(struct pci_dev *dev, int id) >> { >> return (dev->bus->number << 8) + dev->devfn + dev->sriov->offset + >> dev->sriov->stride * id; >> } >> >> #define VIRT_BUS(dev, id) (virtfn_bdf(dev, id) >> 8) >> #define VIRT_DEVFN(dev, id) (virtfn_bdf(dev, id) & 0xff) >> >> We rely on GCC to do CSE and not actually invoke virtfn_bdf more than >> once. > > Yes, that's a good idea. Will replace that function with macros. That's the opposite of most changes lately. I.e., functions (with typechecking) are preferred. -- ~Randy