Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756553Ab3GKUJg (ORCPT ); Thu, 11 Jul 2013 16:09:36 -0400 Received: from mail-oa0-f45.google.com ([209.85.219.45]:60175 "EHLO mail-oa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756512Ab3GKUJe (ORCPT ); Thu, 11 Jul 2013 16:09:34 -0400 MIME-Version: 1.0 In-Reply-To: <51DE8032.4040808@redhat.com> References: <1373535825-49972-1-git-send-email-wangyijing@huawei.com> <1373535825-49972-2-git-send-email-wangyijing@huawei.com> <51DE8032.4040808@redhat.com> From: Bjorn Helgaas Date: Thu, 11 Jul 2013 14:09:11 -0600 Message-ID: Subject: Re: [PATCH -v2 1/3] PCI: introduce PCIe Device Serial Number Capability support To: Don Dutile Cc: Yijing Wang , "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , Rafael , Hanjun Guo , Jiang Liu Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3332 Lines: 107 On Thu, Jul 11, 2013 at 3:51 AM, Don Dutile wrote: > On 07/11/2013 05:43 AM, Yijing Wang wrote: >> >> Introduce PCIe Ext Capability Device Serial Number support, >> so we can use the unique device serial number to identify >> the physical device. During system suspend, if the PCIe >> device was removed and inserted a new same device, after >> system resume there is no good way to identify it, maybe >> Device Serial Number is a good choice if device support. >> >> Signed-off-by: Yijing Wang >> --- >> drivers/pci/pci.c | 27 +++++++++++++++++++++++++++ >> drivers/pci/probe.c | 2 ++ >> include/linux/pci.h | 3 +++ >> 3 files changed, 32 insertions(+), 0 deletions(-) >> >> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c >> index e37fea6..2e855b5 100644 >> --- a/drivers/pci/pci.c >> +++ b/drivers/pci/pci.c >> @@ -2048,6 +2048,33 @@ void pci_free_cap_save_buffers(struct pci_dev *dev) >> } >> >> /** >> + * pci_device_serial_number - get device serial number >> + * @dev: the PCI device >> + * >> + * return the device serial number if device support, >> + * otherwise return 0. >> + */ >> +u64 pci_device_serial_number(struct pci_dev *dev) > > See comment below: > void pci_device_serial_number(struct pci_dev *dev) > > >> +{ >> + int pos; >> + u64 sn; >> + u32 lo, hi; >> + >> + if (!pci_is_pcie(dev)) >> + return 0; >> + > > See comment below: > if (!pci_is_pcie(dev)) { > dev->sn = 0; > return; > > } >> >> + pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DSN); >> + if (!pos) >> + return 0; >> + >> + pci_read_config_dword(dev, pos + 4,&lo); >> + pci_read_config_dword(dev, pos + 8,&hi); >> + sn = ((u64)hi<< 32) | lo; > > See comment below: > dev->sn = ((u64)hi<< 32) | lo; > return; > >> + return sn; >> +} >> +EXPORT_SYMBOL(pci_device_serial_number); >> + >> +/** >> * pci_configure_ari - enable or disable ARI forwarding >> * @dev: the PCI device >> * >> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c >> index 46ada5c..c4c1a2b 100644 >> --- a/drivers/pci/probe.c >> +++ b/drivers/pci/probe.c >> @@ -1322,6 +1322,8 @@ static void pci_init_capabilities(struct pci_dev >> *dev) >> /* Power Management */ >> pci_pm_init(dev); >> >> + dev->sn = pci_device_serial_number(dev); >> + > > Finally, 'the comment below': > I know you were following Bjorn's suggestion, which I thought > was an improvement, but why not do above assignment in > pci_device_serial_number() ? > See above.... pci_device_serial_number() would then have the side-effect of saving the result somewhere, and callers would have to know where to look. Personally, I think it's simpler to return the serial number directly and avoid the side-effect, but maybe this is just bike-shedding. As long as we are bike-shedding, I'd just drop "sn" and do: return ((u64)hi << 32) | lo; And of course, you need spaces before "&hi" and "&lo" in the pci_read_config_dword() calls. -- 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/