Subject: Re: [PATCH] bus/pci: nvme on Windows requires class id and bus

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Hi Tal,

Thanks for the comments.

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+       /* Try and find PCI class ID */
+       for (cp = buf; !(cp[0] == 0 && cp[1] == 0); cp++)

How about
for (cp = buf; cp[0] || cp[1]; cp++)

That would be my preferred idiom, but the DPDK coding style (1.9.1) says 'do
not use ! for tests unless it is a boolean' (but somewhat confusingly does so
in a section on NULL pointers).  I interpreted it as a general prohibition on
conditionals without an explicit operator (except for booleans).  I'd love to be
corrected here!

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+               if (*cp == '&' && sscanf_s(cp, "&CC_%" PRIx32,
+ &class_id) == 1)

Could there be a case where PCI\\VEN_v(4)&DEV_d(4)&CC_c(2)s(2) exist

but PCI\\VEN_v(4)&DEV_d(4)&CC_c(2)s(2)p(2) doesn't? In that case the
parsing would be incorrect.
The MSDN documentation says that the most specific string will be returned
first, in this case &CC_c(2)s(2)p(2), so if there is a 6-digit class ID we will
return it.  That left me wondering what to do if we only encounter a 4-digit
class ID.  If we ignore it, then we won't be able to match on the class ID.  We
could parse it as 4-digits and supply zero for the p(2) field, but that left me
wondering why Windows wouldn't have already done that for us.  What I see
on my own systems is that there is always a 6-digit class ID defined, even if
the pci-ids repository doesn't list any values for p(2) (e.g.
https://pci-ids.ucw.cz/read/PD/07/80 reports as &CC_078000).

My conclusion was that was probably best just to return the first class ID that
Windows reports even if it's only 4-digits.  That way the device can still be
found and will match the CC_ info displayed in device manager.

I'd shift the class_id value to the right in case the returned value is 4 digit, just to verify the result would be "c(2)s(2) 0" and not "0 s(2)p(2)", however when testing your change I couldn't find a case where only 4 digits matched.

Either than that LGTM.

Thanks,
Nick