Re: [PATCH 01/13] wifi: cfg80211: Add provision to advertise multiple radio in one wiphy

Vasanthakumar Thiagarajan
2024-04-14T16:03:10Z

On 4/13/2024 9:10 PM, Ben Greear wrote:
> On 4/12/24 08:58, Ben Greear wrote:
>> On 4/12/24 07:31, Vasanthakumar Thiagarajan wrote:
>
>>> As said, please feel free to propose an alternate solution to address the issue.
>>
>> I do not know the particulars of your driver or driver's needs, but at high level:
>>
>> *  Leave existing wiphy mapping as is.
>> *  Allow adding new combined wiphy(s) on top of groups of underlying physical wiphys.
>> Sort of
>>     like bridges on top of Eth ports.
>> *  The combined wiphy would report underlying wiphy's capabilities (for instance, a
>> combined wiphy on top of
>>     3 single band phys would report itself as tri-band).
>> *  The combined wiphy would add new netlink field listing of its underlying wiphys.
>> User-space wanting to control the combined
>>     wiphy would generally configure the underlying phys (to set 2.4g channel to 6, you'd
>> set the underlying 2.4g
>>     wiphy to channel 6)
>> *  This should require very minimal changes to user space, except of course for new code
>> to actually utilize
>>     the new combined wiphy.
>> *  MLO links and any other logic that needs the combined view would live on the combined
>> wiphy (I understand
>>     from Johannes' comments this is a needed feature.)
>> *  Or user can ignore that combined wiphy entirely and directly use underlying wiphys
>> like we use them currently
>>     for sniffers, stations, aps, combinations thereof.
>> *  Advanced use case could allow combined wiphy to use subset of underlying radios (add
>> combined wiphy on 2.4 and 5g, use 6g for
>>     dedicated mesh backhaul/whatever).
>> *  Interesting logic would be needed to deal with constraints to properly share the
>> underlying resources (you could not
>>     add 16 ap bssid to 2.4 wiphy and also add 16 other ones to the combined wiphy that
>> also uses 2.4 radio most likely,
>>     for instance).  But I think that logic has to be written
>>     either way and is not overly worse with this approach.
>
> I had some further thoughts on this approach:
>
> *  If someone has 2 QCA radio cards, and each radio card has 3 phys, would it be possible
> to have a 6-link MLO
>    setup?
>

As long as supported frequencies of the radios are not overlapping , it is technically
possible to register 6 radios under one wiphy

> *  Could two be200 be combined into a multi-channel concurrent MLO setup with this approach?
>

By nature, MLO device is multi-channel concurrent. Not quite sure about the
be200 capability.

>
> *  For multi-phy arrangements like QCA ath12k and MTK7996, I think the default
> configuration when the driver
>    loads should just be the physical phys by themselves (as mt7996, at least, does it
> now).  This would be fully backwards compatible with
>    current user-space and operation.

There can be configuration knobs in the driver to register it differently...

But the phys would have netlink attributes that
> lets user-space
>    know combined phys (cphys?) can be created on top of them.  User-space that knows
> about MLO can then
>    create the cphy(s) as wanted and build sta/vap/whatever on top of the cphys.
>

Not quite positive on the combined_phy+legacy_phy design as mentioned in the previous mail.

> *  For radios like be200 that are already designed to show a single phy to userspace, they
> would not
>    need any significant change.

As mentioned, it is not lot of changes in hostapd/wpa_s. We'll post them once kernel
part is concluded.

Vasanth