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Message-ID: <cb991a00-fce2-5a3d-c03f-579b44f922f5@quicinc.com>
Date: Fri, 12 Apr 2024 09:41:46 +0530
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Subject: Re: [PATCH 01/13] wifi: cfg80211: Add provision to advertise multiple
 radio in one wiphy
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To: Ben Greear <greearb@candelatech.com>,
        Johannes Berg
	<johannes@sipsolutions.net>,
        Karthikeyan Periyasamy
	<quic_periyasa@quicinc.com>,
        <ath12k@lists.infradead.org>
CC: <linux-wireless@vger.kernel.org>
References: <20240328072916.1164195-1-quic_periyasa@quicinc.com>
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 <72f491f8-dd3a-0c9e-7490-4d51c86f2102@candelatech.com>
From: Vasanthakumar Thiagarajan <quic_vthiagar@quicinc.com>
In-Reply-To: <72f491f8-dd3a-0c9e-7490-4d51c86f2102@candelatech.com>
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On 4/11/2024 2:33 AM, Ben Greear wrote:
> 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.
>>
>>> 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.
> 
> Hello Johannes,
> 
> Is there any design document for the combined phy approach somewhere publicly available?
> 
> It is hard to understand the over all goals by just reading patches as they show up on
> the public mailing lists...
> 

Hi Ben,

I dont think there is a document for this composite phy approach. But we try to clarify
as much as possible in the commit log and kernel-doc. Pls let us know the area which
is more appropriate to be clarified in the path.

Vasanth