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

[Dan Williams <dcbw@redhat.com>]

On Wed, 2015-12-02 at 10:00 -0800, Paul Stewart wrote:
> From my perspective it is useful to have the driver express whether
> or not it supports this parameter.  It may not change how the system
> operates, but it will be useful in testing to determine whether it
> is expected that a (given version of a) driver is expected to act
> with respect to this property so we can flag issues with the
> implementation.

Agreed.

Dan

> On Wed, Dec 2, 2015 at 8:38 AM, Dan Williams <dcbw@redhat.com> wrote:
> > 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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