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

[Ben Greear <greearb@candelatech.com>]

On 4/10/24 08:42, Johannes Berg wrote:
> On Wed, 2024-04-10 at 07:37 -0700, Ben Greear wrote:
>> On 4/10/24 00:56, Johannes Berg wrote:
>>> On Fri, 2024-03-29 at 07:47 -0700, Ben Greear wrote:
>>>> On 3/29/24 07:30, Johannes Berg wrote:
>>>>> On Fri, 2024-03-29 at 19:41 +0530, Vasanthakumar Thiagarajan wrote:
>>>>>>>
>>>>>>>> + * @hw_chans: list of the channels supported by every constituent underlying
>>>>>>>> + *	hardware. Drivers abstracting multiple discrete hardware (radio) under
>>>>>>>> + *	one wiphy can advertise the list of channels supported by each physical
>>>>>>>> + *	hardware in this list. Underlying hardware specific channel list can be
>>>>>>>> + *	used while describing interface combination for each of them.
>>>>>>>
>>>>>>> I'd expect there to be a limit on channels being within a single band on
>>>>>>> a single "hardware"?
>>>>>>>
>>>>>>
>>>>>> There are ath12k hardware supporting multiple band which need to be
>>>>>> registered under one mac80211_hw/wiphy. This design is to support such
>>>>>> hardware.
>>>>>
>>>>> Oh OK, that was something that I didn't have in mind any more, or never
>>>>> knew or paid attention to.
>>>>
>>>> Would it work to leave the phy reporting pretty much as it is now, but add
>>>> a 'associated_peer_radios' list section, so that each phy could report the phys
>>>> associated with it?  Then user-space, driver, mac80211 etc could look up the
>>>> other phys as needed to get a full picture?
>>>>
>>>
>>> There's not really a good way to _do_ that short of creating multiple
>>> wiphys, but that causes _massive_ complexity in the stack (both cfg80211
>>> and mac80211) so we rejected it years ago.
>>
>> I thought the problem ath12k is trying to fix is that there are currently multiple phys (radios) that needed to be made to
>> look like a single phy?
> 
> Correct.
> 
>> For dual and tri-concurrent radios, I think we will need them to look like 3 individual radios for non-MLO use
>> cases
> 
> No, I don't see why, and if you want that we wouldn't support it anyway,
> you'd have to have a module option or something to decide which way to
> go.
> 
> But it really ought to not be needed - the point of these patches is to
> give userspace enough information to know how to (and where) to create
> separate BSSes, with or without MLO between them.

If phy0 told user-space that phy1 and phy2 were 'mlo peers', and phy1 and phy2
gave similar mapping, couldn't user-space just notice the peer group and then
have all the info it needed without the bulk of the patch set in question?

So then if hostapd wants to have 3 radios in an mlo grouping, it can do so.

And if instead it wants three old-style wifi-6 AP interfaces, it could do that
as well.  I don't see why it would need any module option, and I also do not
see why it could not do both behaviours concurrently (one BSSID being MLO, second one
being non MLO, for instance).

>> For instance, mt7996 currently reports 3 single-band wiphys, and each can be used independently.
>> But assuming it starts supporting MLO, then those 3 single band wiphys will need to start acting
>> at least somewhat like a single entity
> 
> Yes.
> 
>> (while also concurrently being able to act as individual
>> wiphys so that one can do a mix of MLO and non MLO sta/AP.)
> 
> No.

How will you allow all three bands/phys to host bssids that can talk to
wifi-6 and earlier stations if there is only a single phy seen by hostapd?

I definitely want to put STA vdevs on the three individual 7996 phys and have them
be able to talk to non MLO APs. This currently works.

I suspect other use cases, such as meshing with non MLO APs may also want
this sort of ability.

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com