linux-kernel - Re: [PATCH v3 0/3] net: dsa: mv88e6xxx: add support for VLAN Table Unit

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Date:	Mon, 6 Jul 2015 20:46:10 -0700
From:	Scott Feldman <sfeldma@...il.com>
To:	Andrew Lunn <andrew@...n.ch>
Cc:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
	Netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Jiri Pirko <jiri@...nulli.us>,
	Florian Fainelli <f.fainelli@...il.com>,
	Guenter Roeck <linux@...ck-us.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	kernel <kernel@...oirfairelinux.com>
Subject: Re: [PATCH v3 0/3] net: dsa: mv88e6xxx: add support for VLAN Table Unit

On Mon, Jul 6, 2015 at 7:00 PM, Andrew Lunn <andrew@...n.ch> wrote:
> On Tue, Jul 07, 2015 at 01:38:04AM +0200, Andrew Lunn wrote:
>> On Sun, Jul 05, 2015 at 10:14:50PM -0400, Vivien Didelot wrote:
>> > Hi all,
>> >
>> > This patchset brings full support for hardware VLANs in DSA, and the Marvell
>> > 88E6xxx compatible switch chips.
>>
>> Hi Vivien
>>
>> I just booted these patches on my board, and i'm getting WARNINGS:
>>
>> [   61.111302] WARNING: CPU: 0 PID: 2751 at net/switchdev/switchdev.c:265 switchdev_port_obj_add+0xd4/0xdc()
>
> Hi Vivien
>
> I debugged this a bit.
>
> The problem comes from:
>
> static int dsa_slave_port_obj_add(struct net_device *dev,
>                                   struct switchdev_obj *obj)
> {
>         int err;
>
>         /*
>          * Skip the prepare phase, since currently the DSA drivers don't need to
>          * allocate any memory for operations and they will not fail to HW
>          * (unless something horrible goes wrong on the MDIO bus, in which case
>          * the prepare phase wouldn't have been able to predict anyway).
>          */
>         if (obj->trans != SWITCHDEV_TRANS_COMMIT)
>                 return 0;
>
>         switch (obj->id) {
>         case SWITCHDEV_OBJ_PORT_VLAN:
>                 err = dsa_slave_port_vlans_add(dev, obj);
>                 break;
>         default:
>                 err = -EOPNOTSUPP;
>                 break;
>         }
>
>         return err;
> }
>
> It is being called with obj->id of 2, which is
> SWITCHDEV_OBJ_IPV4_FIB. This function is called twice. The first time
> it is with SWITCHDEV_TRANS_PREPARE and we are allowed to return an
> error. The second time, with SWITCHDEV_TRANS_COMMIT, errors are not
> allowed.
>
> EOPNOTSUPP is considered an error, so since we don't support
> SWITCHDEV_OBJ_IPV4_FIB we error out the COMMIT phase.
>
> Not sure which is cleaner. Test to see if we support the object during
> the prepare, or allow the commit to accept EOPNOTSUPP as not being an
> error?

I think we should return EOPNOTSUPP on PREPARE, so move the trans !=
COMMIT test inside the case for PORT_VLAN.  That would future-proof
the func when new objects are added to switchdev (and not supported by
dsa_slave).

Does that sound OK?

-scott
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