linux-kernel - Re: [PATCH -v2 1/3] PCI: introduce PCIe Device Serial Number Capability support

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Date:	Thu, 11 Jul 2013 22:43:01 -0400
From:	Don Dutile <ddutile@...hat.com>
To:	Yijing Wang <wangyijing@...wei.com>
CC:	Bjorn Helgaas <bhelgaas@...gle.com>, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, Rafael <rjw@...k.pl>,
	Hanjun Guo <guohanjun@...wei.com>, jiang.liu@...wei.com
Subject: Re: [PATCH -v2 1/3] PCI: introduce PCIe Device Serial Number Capability
 support

On 07/11/2013 09:38 PM, Yijing Wang wrote:
> Hi Don,
>     Thanks for your review and comments very much!
>
>>> +    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() ?
>
> I don't do assignment in pci_device_serial_number() because pci_device_serial_number()
> is an EXPORT_SYMBOL, and will be used to get dsn for non-scaned device, for example:
>
> 1. we have pcie device in slot before suspend.
> 2. we removed the device during suspend.
> 3. we reinserted a new device during suspend.
> 4. we should check the device change during resume, so we
> try to use pcie device serial number to identify changes.
> But the pci_dev structure maybe the old stale data. So
> I prefer to get dsn by return.
>
> what about this:
>
> static void pci_init_capabilities(struct pci_dev *dev)
>      ........
>      pci_dsn_init(dev);
>      ..........
>
>
> void pci_dsn_init(dev)
> {
>      dev->sn = pci_device_serial_number(dev);
> }
>
>
>
Looks good!  I think that meets all the uses (use in init, post-suspend).
- Don

>> See above....
>> - Don
>>
>>>        /* Vital Product Data */
>>>        pci_vpd_pci22_init(dev);
>>>
>>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>>> index 0fd1f15..10d190b 100644
>>> --- a/include/linux/pci.h
>>> +++ b/include/linux/pci.h
>>> @@ -342,6 +342,7 @@ struct pci_dev {
>>>        struct list_head msi_list;
>>>        struct kset *msi_kset;
>>>    #endif
>>> +    u64 sn;        /* device serieal number, 0 if not support */
>>>        struct pci_vpd *vpd;
>>>    #ifdef CONFIG_PCI_ATS
>>>        union {
>>> @@ -995,6 +996,8 @@ ssize_t pci_read_vpd(struct pci_dev *dev, loff_t pos, size_t count, void *buf);
>>>    ssize_t pci_write_vpd(struct pci_dev *dev, loff_t pos, size_t count, const void *buf);
>>>    int pci_vpd_truncate(struct pci_dev *dev, size_t size);
>>>
>>> +u64 pci_device_serial_number(struct pci_dev *dev);
>>> +
>>>    /* Helper functions for low-level code (drivers/pci/setup-[bus,res].c) */
>>>    resource_size_t pcibios_retrieve_fw_addr(struct pci_dev *dev, int idx);
>>>    void pci_bus_assign_resources(const struct pci_bus *bus);
>>
>>
>> .
>>
>
>

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