[U-Boot] [PATCH] pci: don't skip vendor ID 0

[Gregory Fong]

On Thu, Jan 26, 2017 at 5:57 AM, Leon Woestenberg <leon at sidebranch.com> wrote:
>
> On Thu, Jan 26, 2017 at 2:19 PM, Gregory Fong <gregory.0xf0 at gmail.com>
> wrote:
>>
>>  It looks like the main problem is that
>> struct pci_device_id with vendor and device both 0 is being used to
>> indicate the end of an array.  Not that complicated to change, but it
>> isn't trivial either, so figure it's best to leave for a future
>> changeset.
>>
> Hmm, then maybe 0xFFFF, 0xFFFF should be used to indicate the end of the
> array.
>
> How does Linux handle the end of the array, while it also supports 0x0000,
> 0x0000?

Well, looking at
http://lxr.free-electrons.com/source/drivers/pci/pci-driver.c , in
pci_match_id(), it stops if !(vendor || subvendor || class_mask), so
I'd hazard a guess that the device I have is working is because it has
a nonzero class ID.  Strictly speaking that is probably still invalid,
but it's much less likely to happen.  It also supports dynamic IDs for
which it iterates over a linked list.

Unfortunately there seems to be a fair bit of code relying on all 0s
having a special meaning, and it looks like all PCI_ANY_ID has its own
meaning as well based off of the fact that there's a static
pci_device_id_any struct in there that's used if driver_override is
set in the input struct pci_dev.  I can't say more than that without
digging into the log for that change or finding the users of the
driver_override flag.

Best regards,
Gregory