netdev - Re: [PATCH RFC 2/2] net: dsa: bcm_sf2: implement HW bridging operations

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Date:	Thu, 19 Feb 2015 22:56:56 -0500
From:	Andy Gospodarek <gospo@...ulusnetworks.com>
To:	Florian Fainelli <f.fainelli@...il.com>
Cc:	roopa <roopa@...ulusnetworks.com>,
	Guenter Roeck <linux@...ck-us.net>, netdev@...r.kernel.org,
	davem@...emloft.net, vivien.didelot@...oirfairelinux.com,
	jerome.oufella@...oirfairelinux.com, andrew@...n.ch,
	cphealy@...il.com
Subject: Re: [PATCH RFC 2/2] net: dsa: bcm_sf2: implement HW bridging
 operations

On Thu, Feb 19, 2015 at 10:20:58PM -0500, Andy Gospodarek wrote:
> On Thu, Feb 19, 2015 at 06:00:22PM -0800, Florian Fainelli wrote:
> > On 19/02/15 17:46, roopa wrote:
> > > On 2/19/15, 5:03 PM, Guenter Roeck wrote:
> > >> On Thu, Feb 19, 2015 at 04:51:30PM -0800, roopa wrote:
> > >>>> Not sure yet what to do about setting the fdb aging time. I don't see a
> > >>>> mechanism to do that. No idea how important that is.
> > >>> rocker, the only consumer today relies on the bridge driver aging of
> > >>> learnt
> > >>> entries.
> > >>> You could do the same.
> > >>>
> > >> Remember that we are dealing with hardware switch chips. Those chips
> > >> won't time out fdb entries just because the kernel's bridge driver
> > >> thinks that it should.
> > > Oh, they dont..?. sorry,  I dont know the details about your hardware.
> > > But, if these are entries learnt by hw, there should be a hw config to
> > > age them (I guess that is what you are talking about). Which the swicth
> > > driver can set.
> > > If you disable hw aging, you can sync these entries to the bridge
> > > driver, and make the bridge driver age them followed by a subsequent
> > > delete in hw.
> > 
> > The SF2 HW has and aging and a valid bit available, I guess my question
> > would be, do we have anything today in "net-next" that allows
> > configuring HW aging vs. SW aging (implying doing a HW to SW sync)?
> 
> Yes, the setting of the BR_LEARNING_SYNC bit in bridge port flags should
> signal to the hardware that it should send learning notifications up to
> the kernel bridge.  This is set via the IFLA_BRPORT_LEARNING attribute
> in a setlink message.

Sorry I should offer some clarification on this point.  The flag I
mentioned is only used to signal to drivers that they should notify the
core kernel about new MACs that are learned.

If there is a need for different driver behavior depending on whether
hardware learning is enabled or not it might be time to add a
configuration option up into the stack.
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