[U-Boot] [PATCH] pci: don't skip vendor ID 0
Leon Woestenberg
leon at sidebranch.com
Thu Jan 26 13:26:09 CET 2017
Hello all,
my two cents on this one:
On Thu, Jan 26, 2017 at 11:08 AM, Bin Meng <bmeng.cn at gmail.com> wrote:
> >> On Wed, Jan 25, 2017 at 1:25 PM, Gregory Fong
> >> <Gregory.Fong at virgingalactic.com> wrote:
> >> > I've been looking through the book I have on PCI and through various
> online
> >> > resources, and haven't been able to find evidence that a vendor ID of
> 0 is
> >> > invalid, even if it's unusual.
>
> Is it possible that it's zero due to the hardware is buggy? For
> example, on some Intel cards, PCI vendor ID and device ID can be
> loaded from an EEPROM and if EEPROM content is wrong, it may expose
> wrong IDs. Anyway zero does not look like a valid one though.
>
> Regards,
> Bin
>
>From the spec. point of view, 0x0000 seems as valid as any in the range
[0x0001-0xFFFE].
>From the registry point of view, only registered numbers are valid.
I.e. if I create a programmable PCI(e) card, I can pick any number in the
range [0x0000-0xFFFE] during development and it should work. I will try not
to clash with already registered numbers (to prevent the wrong drivers
probing the endpoint), and preferably I would try to re-use the (FPGA)
silicon vendor's ID, although I am well aware that it should change going
into production.
If only 0xFFFF is reserved, then [0-0xFFFE] should be accepted in the code,
right?
If we disallow 0x0000, on what arguments do we do that?
Middle solution is to accept the ID with a warning.
Regards,
Leon.
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