staging: dpaa2-ethsw: check if there is space for a new VLAN

Avoid getting into a WARNING as below by checking, while in the prepare
state of the transactional operation, if there is space for a new VLAN.
If we reached the maximum number, return an appropriate error.

[ 6503.657564] eth3: Commit of object (id=1) failed.
[ 6503.657588] WARNING: CPU: 2 PID: 17144 at net/switchdev/switchdev.c:277 switchdev_port_obj_add_now+0xcc/0x110
...
[ 6503.657628] x1 : 70887ce26695c500 x0 : 0000000000000000
[ 6503.657630] Call trace:
[ 6503.657633]  switchdev_port_obj_add_now+0xcc/0x110
[ 6503.657635]  switchdev_port_obj_add+0x40/0xc0
[ 6503.657638]  br_switchdev_port_vlan_add+0x50/0x78
[ 6503.657640]  __vlan_add+0x2dc/0x758
[ 6503.657642]  nbp_vlan_add+0xc0/0x180
[ 6503.657644]  br_vlan_info.isra.0+0x68/0x128
[ 6503.657646]  br_process_vlan_info+0x224/0x2f8
[ 6503.657647]  br_afspec+0x158/0x188
[ 6503.657649]  br_setlink+0x1a4/0x290
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Link: https://lore.kernel.org/r/20200721091919.20394-7-ioana.ciornei@nxp.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fsl-dpaa2/ethsw/ethsw.c

@@ -979,10 +979,27 @@ static int port_vlans_add(struct net_device *netdev,
 			  struct switchdev_trans *trans)
 {
 	struct ethsw_port_priv *port_priv = netdev_priv(netdev);
-	int vid, err = 0;
+	struct ethsw_core *ethsw = port_priv->ethsw_data;
+	struct dpsw_attr *attr = &ethsw->sw_attr;
+	int vid, err = 0, new_vlans = 0;
+
+	if (switchdev_trans_ph_prepare(trans)) {
+		for (vid = vlan->vid_begin; vid <= vlan->vid_end; vid++)
+			if (!port_priv->ethsw_data->vlans[vid])
+				new_vlans++;
+
+		/* Check if there is space for a new VLAN */
+		err = dpsw_get_attributes(ethsw->mc_io, 0, ethsw->dpsw_handle,
+					  &ethsw->sw_attr);
+		if (err) {
+			netdev_err(netdev, "dpsw_get_attributes err %d\n", err);
+			return err;
+		}
+		if (attr->max_vlans - attr->num_vlans < new_vlans)
+			return -ENOSPC;
 
-	if (switchdev_trans_ph_prepare(trans))
 		return 0;
+	}
 
 	for (vid = vlan->vid_begin; vid <= vlan->vid_end; vid++) {
 		if (!port_priv->ethsw_data->vlans[vid]) {