Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756690Ab3GLDiV (ORCPT ); Thu, 11 Jul 2013 23:38:21 -0400 Received: from mail-ob0-f173.google.com ([209.85.214.173]:37466 "EHLO mail-ob0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756475Ab3GLDiT (ORCPT ); Thu, 11 Jul 2013 23:38:19 -0400 MIME-Version: 1.0 In-Reply-To: <51DEF6DD.1070406@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> <51DEF6DD.1070406@redhat.com> From: Bjorn Helgaas Date: Thu, 11 Jul 2013 21:37:58 -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: 4704 Lines: 144 On Thu, Jul 11, 2013 at 12:18 PM, Don Dutile wrote: > 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. Good point, BTW. I hadn't thought about it from that angle. > 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... :-/ Of course, for Yijing's use, it's important that we're able to get the *non-cached* serial number, because the cached one belongs to the old, pre-suspend device, and we want to look at the post-suspend device to see if it's the same. Sigh. I dunno, I'll have to finish sorting through this in a week or so... (I'll be on vacation for the next few days.) 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/