Re: [PATCH v3] wifi: cfg80211: check radio iface combination for multi radio per wiphy

[Johannes Berg <johannes@sipsolutions.net>]

On Wed, 2024-09-11 at 20:51 +0530, Karthikeyan Periyasamy wrote:
> 
> ieee80211_link_reserve_chanctx() calls 
> ieee80211_can_create_new_chanctx() with radio_idx (-1) to calculate the 
> max channel (ieee80211_max_num_channels) after the iface combination 
> check (cfg80211_iter_combinations) passed for the global iface 
> combination. Here the expectation is number of channel context is less 
> than the number of different channel. So in multi-radio advertisement, 
> each radio support atleast one channel, so totally multiple different 
> channels advertised in the global iface combination to pass this 
> ieee80211_max_num_channels().

So maybe that's broken then, I dunno. You should figure it out with
Felix I guess.

The intent was, and clearly it has to be, that the global combinations
are something that can be handled regardless of radio information, to be
backward compatible with existing uses. Therefore, it cannot be
something where you say two channels and radar detection on both because
that would imply being able to use channels 36 and 40 with 20 MHz at the
same time with radar detection, which isn't actually possible.
In this case, the "two channels" is only possible with also two radios,
which has to rely on the per-radio advertisement, and the global one has
to be just one channel for radar detection.

We still need the part of the patch that calls the validation on each
radio, but it shouldn't be different from the global one. If you could
make that patch I'd appreciate it.

johannes