Date:   Thu, 6 Jul 2017 14:36:42 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Arkadi Sharshevsky <arkadis@...lanox.com>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, jiri@...nulli.us, ivecera@...hat.com,
        andrew@...n.ch, vivien.didelot@...oirfairelinux.com,
        Woojung.Huh@...rochip.com, stephen@...workplumber.org,
        mlxsw@...lanox.com
Subject: Re: [PATCH net-next RFC 08/12] net: dsa: Remove support for bypass
 bridge port attributes/vlan set

On 07/06/2017 04:00 AM, Arkadi Sharshevsky wrote:
> 
> 
> On 07/05/2017 10:45 PM, Florian Fainelli wrote:
>> On 07/05/2017 08:36 AM, Arkadi Sharshevsky wrote:
>>> The bridge port attributes/vlan for DSA devices should be set only
>>> from bridge code. Furthermore, The vlans are synced totally with the
>>> bridge so there is no need for special dump support.
>>>
>>> Signed-off-by: Arkadi Sharshevsky <arkadis@...lanox.com>
>>
>> I would be more comfortable if we still had a way to dump HW entries by
>> calling into drivers, because it's useful for debugging, and doing that
>> using standard tools plus an additional flag for instance:
>>
>> bridge fdb show
>>
>> would dump the SW-maintained VLANs, but:
>>
>> bridge fdb show hw
>>
> 
> I agree that in your case, the FDBs are exception because they cannot be
> synced with the sw bridge due to lack of interrupt per learned entry,
> but note that this ability of bypass dump should not be supported by
> switchdev code because its contradicts the model. That is why I moved it
> inside DSA in one of the following patches (another reason is that
> nobody is using it beside you so there is no reason to leave it there).

Sure, I agree with that, no need to clutter switchdev and other
switchdev only drivers like mlxsw with FDB dumping code that they don't
need.

> 
> This is especially true for vlans which are synced completely with the
> software bridge.
> 
> Regarding debugging, if you want to see the hardware tables you can
> easily use dpipe for that. For example you can add table which does
> match on vlan and mac and set the output port, or some table that
> matches port and incoming packets vlan into internal metadata (FID)
> that can be used for lookup.
> 
> I just don't think it is good idea for mixing this tools together.

Well, that is once again debatable, ethtool for instance contains a
collection of debug and functional information about your hardware.
Having the ability to dump the VLAN tables using the standard bridge
vlan output has a lot of value in that you can easily correlated whether
the SW representation matches the HW representation (as fed by the
driver back into bridge's netlink messages).

> 
>> would dump the HW-maintained VLANs, or any flag name really, but the
>> point is that we can keep using a standard tool to expose debugging
>> features. debugfs (or something else) could be used, but was rejected by
>> David.
>>
>> Also, technically, it ought to be possible to configure a port's VLAN
>> membership (although using poor semantics) through e.g: vconfig add
>> sw0p0 1, which would call ndo_vlan_rx_add_vid() (DSA does not support it
>> but mlxsw does), and so being able to dump that configuration would be
> 
> Yeah, in mlxsw the vlan devices are used mainly for vlan unaware bridge,
> so the vlans will not be visible by the bridge, but the correct API to
> see this is via:
> 
> $ip -d link show sw1p7.8

Since the VLAN-aware device is visible to user-space, my comment does
not really make sense in that this very interface existence indicates
that the port has been properly set up with a VLAN tag
-- 
Florian

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