Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756930Ab3GKWSW (ORCPT ); Thu, 11 Jul 2013 18:18:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59468 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754572Ab3GKWSU (ORCPT ); Thu, 11 Jul 2013 18:18:20 -0400 Message-ID: <51DEF6DD.1070406@redhat.com> Date: Thu, 11 Jul 2013 14:18:05 -0400 From: Don Dutile User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.12) Gecko/20130108 Thunderbird/10.0.12 MIME-Version: 1.0 To: Bjorn Helgaas CC: Yijing Wang , "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , Rafael , Hanjun Guo , Jiang Liu Subject: Re: [PATCH -v2 1/3] PCI: introduce PCIe Device Serial Number Capability support References: <1373535825-49972-1-git-send-email-wangyijing@huawei.com> <1373535825-49972-2-git-send-email-wangyijing@huawei.com> <51DE8032.4040808@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4231 Lines: 124 On 07/11/2013 04:09 PM, Bjorn Helgaas wrote: > 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. Ah, like so many other features of a PCI device? -- what are all those flags/status bits in pdev for ??? ;-) > Personally, I think it's simpler to return the serial number directly > and avoid the side-effect, but maybe this is just bike-shedding. > What struck me about rtning a value is in pci_init_capabilities(), it was the only function with a rtn value that had to be put into a pci_dev struct element, while all the others stored their related capabilities in the pdev, or other struct related to it. So, maybe there should be a "pci_device_serial_number_init()" function which does the storage in the pdev struct, and another (wrapper, dare I shoot myself, inline) that is "pci_device_serial_number()" that returns the value of the pdev's sn element, if another module or other core component want to get it. .... and do that in a future patch... :-/ > 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/