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

[Karthikeyan Periyasamy <quic_periyasa@quicinc.com>]

On 9/11/2024 7:10 PM, Johannes Berg wrote:
> On Wed, 2024-09-11 at 18:45 +0530, Karthikeyan Periyasamy wrote:
>>> I guess it depends on how you interpret "combined". It must be something
>>> that can actually be done *regardless* of radio assignment, to be
>>> compatible with older userspace.
>>>
>>> So if you think "combined" == "superset of all radios" then your
>>> understanding is incorrect. You need to think "combined" == "what the
>>> device can do without caring about radio assignment".
>>>
>> The current implementation of radio specific advertisement global iface
>> combination (NL80211_ATTR_WIPHY_INTERFACE_COMBINATIONS) expects the
>> superset of all radios, wherever the radio idx is -1 from caller of
>> cfg80211_iter_combinations().
> 
> How so?
> 

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().

-- 
Karthikeyan Periyasamy
--
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