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Message-ID: <614bb8a8f1d9174ad7d87cf7636f657cda7b1ef9.camel@sipsolutions.net>
Subject: Re: [PATCH 01/13] wifi: cfg80211: Add provision to advertise
 multiple radio in one wiphy
From: Johannes Berg <johannes@sipsolutions.net>
To: Ben Greear <greearb@candelatech.com>, Vasanthakumar Thiagarajan
 <quic_vthiagar@quicinc.com>, Karthikeyan Periyasamy
 <quic_periyasa@quicinc.com>,  ath12k@lists.infradead.org
Cc: linux-wireless@vger.kernel.org
Date: Wed, 10 Apr 2024 17:42:09 +0200
In-Reply-To: <20b56e52-a5e2-70cd-a62a-8c4a3526c2cf@candelatech.com>
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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:
> > > > > >=20
> > > > > > > + * @hw_chans: list of the channels supported by every consti=
tuent 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 chann=
el list can be
> > > > > > > + *	used while describing interface combination for each of t=
hem.
> > > > > >=20
> > > > > > I'd expect there to be a limit on channels being within a singl=
e band on
> > > > > > a single "hardware"?
> > > > > >=20
> > > > >=20
> > > > > There are ath12k hardware supporting multiple band which need to =
be
> > > > > registered under one mac80211_hw/wiphy. This design is to support=
 such
> > > > > hardware.
> > > >=20
> > > > Oh OK, that was something that I didn't have in mind any more, or n=
ever
> > > > knew or paid attention to.
> > >=20
> > > Would it work to leave the phy reporting pretty much as it is now, bu=
t add
> > > a 'associated_peer_radios' list section, so that each phy could repor=
t the phys
> > > associated with it?  Then user-space, driver, mac80211 etc could look=
 up the
> > > other phys as needed to get a full picture?
> > >=20
> >=20
> > There's not really a good way to _do_ that short of creating multiple
> > wiphys, but that causes _massive_ complexity in the stack (both cfg8021=
1
> > and mac80211) so we rejected it years ago.
>=20
> 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 lik=
e 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 wi=
ll 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.

johannes