netdev - Re: [RFC net-next 1/3] net: marvell: prestera: Add Switchdev driver for Prestera family ASIC device 98DX325x (AC3x)

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Date:   Tue, 5 May 2020 07:01:43 +0300
From:   Vadym Kochan <vadym.kochan@...ision.eu>
To:     Ido Schimmel <idosch@...sch.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Oleksandr Mazur <oleksandr.mazur@...ision.eu>,
        Taras Chornyi <taras.chornyi@...ision.eu>,
        Serhiy Boiko <serhiy.boiko@...ision.eu>,
        Andrii Savka <andrii.savka@...ision.eu>,
        Volodymyr Mytnyk <volodymyr.mytnyk@...ision.eu>,
        Serhiy Pshyk <serhiy.pshyk@...ision.eu>
Subject: Re: [RFC net-next 1/3] net: marvell: prestera: Add Switchdev driver
 for Prestera family ASIC device 98DX325x (AC3x)

Hi Ido,

On Sat, May 02, 2020 at 06:20:49PM +0300, Vadym Kochan wrote:
> Hi Ido,
> 
> On Thu, Mar 05, 2020 at 04:49:37PM +0200, Ido Schimmel wrote:
> > On Tue, Feb 25, 2020 at 04:30:54PM +0000, Vadym Kochan wrote:
> > > +int mvsw_pr_port_learning_set(struct mvsw_pr_port *port, bool learn)
> > > +{
> > > +	return mvsw_pr_hw_port_learning_set(port, learn);
> > > +}
> > > +
> > > +int mvsw_pr_port_flood_set(struct mvsw_pr_port *port, bool flood)
> > > +{
> > > +	return mvsw_pr_hw_port_flood_set(port, flood);
> > > +}
> > 
> > Flooding and learning are per-port attributes? Not per-{port, VLAN} ?
> > If so, you need to have various restrictions in the driver in case
> > someone configures multiple vlan devices on top of a port and enslaves
> > them to different bridges.

Yes, and there is no support for vlan device on top of the port.

> > 
> > > +
> > > +
> > > +	INIT_LIST_HEAD(&port->vlans_list);
> > > +	port->pvid = MVSW_PR_DEFAULT_VID;
> > 
> > If you're using VID 1, then you need to make sure that user cannot
> > configure a VLAN device with with this VID. If possible, I suggest that
> > you use VID 4095, as it cannot be configured from user space.
> > 
> > I'm actually not entirely sure why you need a default VID.
> > 
>  
> > > +mvsw_pr_port_vlan_bridge_join(struct mvsw_pr_port_vlan *port_vlan,
> > > +			      struct mvsw_pr_bridge_port *br_port,
> > > +			      struct netlink_ext_ack *extack)
> > > +{
> > > +	struct mvsw_pr_port *port = port_vlan->mvsw_pr_port;
> > > +	struct mvsw_pr_bridge_vlan *br_vlan;
> > > +	u16 vid = port_vlan->vid;
> > > +	int err;
> > > +
> > > +	if (port_vlan->bridge_port)
> > > +		return 0;
> > > +
> > > +	err = mvsw_pr_port_flood_set(port, br_port->flags & BR_FLOOD);
> > > +	if (err)
> > > +		return err;
> > > +
> > > +	err = mvsw_pr_port_learning_set(port, br_port->flags & BR_LEARNING);
> > > +	if (err)
> > > +		goto err_port_learning_set;
> > 
> > It seems that learning and flooding are not per-{port, VLAN} attributes,
> > so I'm not sure why you have this here.
> > 
> > The fact that you don't undo this in mvsw_pr_port_vlan_bridge_leave()
> > tells me it should not be here.
> > 
> 
>  > +
> > > +void
> > > +mvsw_pr_port_vlan_bridge_leave(struct mvsw_pr_port_vlan *port_vlan)
> > > +{
> > > +	struct mvsw_pr_port *port = port_vlan->mvsw_pr_port;
> > > +	struct mvsw_pr_bridge_vlan *br_vlan;
> > > +	struct mvsw_pr_bridge_port *br_port;
> > > +	int port_count;
> > > +	u16 vid = port_vlan->vid;
> > > +	bool last_port, last_vlan;
> > > +
> > > +	br_port = port_vlan->bridge_port;
> > > +	last_vlan = list_is_singular(&br_port->vlan_list);
> > > +	port_count =
> > > +	    mvsw_pr_bridge_vlan_port_count_get(br_port->bridge_device, vid);
> > > +	br_vlan = mvsw_pr_bridge_vlan_find(br_port, vid);
> > > +	last_port = port_count == 1;
> > > +	if (last_vlan) {
> > > +		mvsw_pr_fdb_flush_port(port, MVSW_PR_FDB_FLUSH_MODE_DYNAMIC);
> > > +	} else if (last_port) {
> > > +		mvsw_pr_fdb_flush_vlan(port->sw, vid,
> > > +				       MVSW_PR_FDB_FLUSH_MODE_DYNAMIC);
> > > +	} else {
> > > +		mvsw_pr_fdb_flush_port_vlan(port, vid,
> > > +					    MVSW_PR_FDB_FLUSH_MODE_DYNAMIC);
> > 
> > If you always flush based on {port, VID}, then why do you need the other
> > two?
> > 
> 
>  > +
> > > +static int mvsw_pr_port_obj_attr_set(struct net_device *dev,
> > > +				     const struct switchdev_attr *attr,
> > > +				     struct switchdev_trans *trans)
> > > +{
> > > +	int err = 0;
> > > +	struct mvsw_pr_port *port = netdev_priv(dev);
> > > +
> > > +	switch (attr->id) {
> > > +	case SWITCHDEV_ATTR_ID_PORT_STP_STATE:
> > > +		err = -EOPNOTSUPP;
> > 
> > You don't support STP?
> 
> Not, yet. But it will be in the next submission or official patch.
> > 
> > > +		break;
>  
> > > +	default:
> > > +		kfree(switchdev_work);
> > > +		return NOTIFY_DONE;
> > > +	}
> > > +
> > > +	queue_work(mvsw_owq, &switchdev_work->work);
> > 
> > Once you defer the operation you cannot return an error, which is
> > problematic. Do you have a way to know if the operation will succeed or
> > not? That is, if the hardware has enough space for this new FDB entry?
> > 
> Right, fdb configuration on via fw is blocking operation I still need to
> think on it if it is possible by current design.
> 
> 
> > 
> > Why do you need both 'struct mvsw_pr_switchdev' and 'struct
> > mvsw_pr_bridge'? I think the second is enough. Also, I assume
> > 'switchdev' naming is inspired by mlxsw, but 'bridge' is better.
> > 
> I changed to use bridge for bridge object, because having bridge_device
> may confuse.
> 
> Thank you for your comments they were very useful, sorry for so late
> answer, I decided to re-implement this version a bit. Regarding flooding
> and default vid I still need to check it.
> 
> Regards,
> Vadym Kochan