Re: [PATCH 08/11] brcmfmac: Make 5G join preference configurable.

From: Dan Williams <dcbw@redhat.com>
To: Arend van Spriel <arend@broadcom.com>, Jouni Malinen <j@w1.fi>,
	Kalle Valo <kvalo@codeaurora.org>
Cc: linux-wireless <linux-wireless@vger.kernel.org>,
	Hante Meuleman <meuleman@broadcom.com>
Subject: Re: [PATCH 08/11] brcmfmac: Make 5G join preference configurable.
Date: Wed, 02 Dec 2015 10:38:51 -0600	[thread overview]
Message-ID: <1449074331.21648.2.camel@redhat.com> (raw)
In-Reply-To: <565EF307.90002@broadcom.com>

On Wed, 2015-12-02 at 14:32 +0100, Arend van Spriel wrote:
> On 12/01/2015 12:08 PM, Jouni Malinen wrote:
> > On Tue, Dec 01, 2015 at 11:48:32AM +0200, Kalle Valo wrote:
> > > Arend van Spriel <arend@broadcom.com> writes:
> > > > It solves a problem for us, but admittedly it is not something
> > > > that is
> > > > very usable by user-space apps. So I guess what you are
> > > > suggesting
> > > > here is to come up with a nl80211 api for this. On the mailing
> > > > list
> > > > (or hostap list) the topic pops up from time to time so there
> > > > are
> > > > people who would like to have such a knob to play with. Still
> > > > would
> > > > like to keep the module parameter although its use may change
> > > > when
> > > > nl80211 api is added.
> > > 
> > > I don't know what is the best approach, that's why I would like
> > > to hear
> > > opinions from others. Personally I don't like the idea of adding
> > > 802.11
> > > level configuration options to module parameters, but on the
> > > other hand
> > > I don't have any strong opinions about this.
> > 
> > I would like to see this as a new attribute to NL80211_CMD_CONNECT
> > to
> > provide parameters for offloaded (driver and/or firmware) BSS
> > selection
> > and roaming. If there is a driver that uses roaming offload with
> > NL80211_CMD_ASSOCIATE, the same attribute could be used there (but
> > I'm
> > not sure how exact such offloading would work in practice since I'd
> > expect both authentication and (re)association to be offloaded).
> 
> Sounds reasonable. Just would like to explore the use-case a bit
> more. 
> Looking at tools like NetworkManager and android network list, the
> user 
> is always presented with just SSID listed once. For NetworkManager 
> 
While NM has band locking properties, there is currently no "prefer
5ghz" since as Jouni said, the supplicant should probably just prefer
5ghz right now.  In any case, the best path from an NM perspective
would be a supplicant per-network property that would then be sent for
CONNECT-capable drivers, or which the supplicant would manually handle
for softmac drivers through its existing AP selection code.

Dan

> details can be configured for a connection and the bss selection 
> parameters could be one of those. What level of detail would be
> needed 
> there. Not saying we can not have more detail in the nl80211 API.
> 
> > > I guess we have two different designs, one where the roaming
> > > logic is in
> > > firmware and other where wpasupplicant is responsible for this.
> > > (And I
> > > assume that brcfmac belongs to the former group.) Ideally it
> > > would be
> > > nice that we would have a same configuration knob for both but I
> > > don't
> > > know if that's really feasible.
> > 
> > Both of these would work as long as wpa_supplicant has means for
> > providing such configuration to the driver in a generic manner.
> > That
> > NL80211_CMD_CONNECT extension with a new optional attribute would
> > be
> > such a generic design.
> 
> So does the driver need to advertise support for bss selection 
> parameters or can it simply ignore the parameters. Assuming the
> latter 
> for now.
> 
> Regards,
> Arend
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