[RFC wireless-next 0/8] initial UHR NPCA support

[Johannes Berg <johannes@sipsolutions.net>]

Here's the UHR Non-Primary Channel ACcess (NPCA) support I've been
working on.

The idea is to represent the NPCA channel/puncturing in the chandef
and have the other parameters per link. That's maybe not compeletely
right, but having them all in the chandef seemed too complex, and
these have to be there to be able to set up things.

There is, however, a problem with the way I've done this: I'm now
checking that NPCA is legal, i.e. the NPCA primary channel [sic]
is actually in the second half of the chandef. This cause problems
when adding DBE, because DBE extends the chandef as well, and you
could have, for 320 MHz:

| p |   |   |   | n |   |   |   |   |   |   |   |   |   |   |   |
| BSS Channel                   |
                | NPCA channel  |
| DBE Channel                                                   |

p = primary channel
n = NPCA primary channel

so that the NPCA isn't actually in the second half. I think now
the right way is to actually represent it as in the picture, but
it seems the spec is also still evolving wrt. the intersection of
NPCA and DBE. Some folks want NPCA to be in DBE but that doesn't
seem to work well (to me) with puncturing patterns etc.

So I think I'm probably going to change the chandef validation on
top of these changes when adding DBE, and then we need a separate
NPCA validation function for mac80211 instead, but that seems OK.


This is based on the patches I sent a few minutes ago:
https://lore.kernel.org/linux-wireless/20260303152558.00e7bc8e9f4b.Iafdf37fb0f4304bdcdb824977d61e17b38c47685@changeid/T/#u
https://lore.kernel.org/linux-wireless/20260303142641.273071-5-johannes@sipsolutions.net/T/#t

johannes