Re: [PATCH 7/8] pci: Add CircuitCo VENDOR ID and MinnowBoard DEVICE ID

[Bjorn Helgaas]

On Wed, Jun 26, 2013 at 3:30 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> On 06/26/2013 12:37 PM, Bjorn Helgaas wrote:
>>
>> Yeah, that's what I was thinking.
>>
>> But Peter's comment makes more sense to me now.  The spec refers to
>> that config register as "Subsystem ID," not "Subsystem Device ID," but
>> I was confused because most existing usage treats it as a device ID.
>> For example, the field in struct pci_device_id is named "subdevice,"
>> and all the existing #defines in pci_ids.h are of the form
>> PCI_SUBDEVICE_ID_*.
>>
>> Device IDs are pretty specific identifiers, so I was thinking that a
>> "sub-device ID" would be even more specific.  Then it would make no
>> sense to have a "sub-device ID" that was as generic as "MINNOWBOARD."
>> But the register is actually *not* a "sub-device ID," and I can see
>> that using the same Subsystem ID for all the devices on a board might
>> make sense.
>>
>
> Subsystem IDs is basically a board ID in the traditional PC view, but
> they didn't call it that because it would have been confusing in other,
> nontraditional configurations.
>
> Microsoft has a "best practices" document, which may end up becoming
> basis for a future PCI-SIG document clarifying the standard:
>
> http://msdn.microsoft.com/en-us/library/windows/hardware/gg463287.aspx

Interesting, thanks for the link.  If I read that correctly, the
MinnowBoard is basically a motherboard, and any board layout change or
component value change will require a new Subsystem ID, which will in
turn require a pch_gbe update.  That doesn't sound optimal, but maybe
people don't actually interpret it that strictly.

Bjorn
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