Hi,

On Wed, Feb 16, 2022 at 02:29:34PM +0100, Tobias Waldekranz wrote:

+static int mv88e6xxx_sid_new(struct mv88e6xxx_chip *chip, u8 *sid)
+{
+	DECLARE_BITMAP(busy, MV88E6XXX_N_SID) = { 0 };
+	struct mv88e6xxx_mst *mst;
+
+	set_bit(0, busy);
+
+	list_for_each_entry(mst, &chip->msts, node) {
+		set_bit(mst->stu.sid, busy);
+	}

Do you need these set_bit() operations to be atomic? Would __set_bit()
produce better code?

+
+	*sid = find_first_zero_bit(busy, MV88E6XXX_N_SID);
+
+	return (*sid >= mv88e6xxx_max_sid(chip)) ? -ENOSPC : 0;

Hmm. Let's hope that mv88e6xxx_max_sid() never returns a value larger
than MV88E6XXX_N_SID.

+}
+

...

+static int mv88e6xxx_sid_get(struct mv88e6xxx_chip *chip, struct net_device *br,
+			     u16 mstid, u8 *sid)
+{
+	struct mv88e6xxx_mst *mst;
+	int err;
+
+	if (!br)
+		return 0;
+
+	if (!mv88e6xxx_has_stu(chip))
+		return -EOPNOTSUPP;
+
+	list_for_each_entry(mst, &chip->msts, node) {
+		if (mst->br == br && mst->mstid == mstid) {
+			refcount_inc(&mst->refcnt);
+			*sid = mst->stu.sid;
+			return 0;
+		}
+	}
+
+	err = mv88e6xxx_sid_new(chip, sid);
+	if (err)
+		return err;
+
+	mst = kzalloc(sizeof(*mst), GFP_KERNEL);
+	if (!mst)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&mst->node);

There is no need to initialise the node if you're then going to be
adding it to the list.

+	refcount_set(&mst->refcnt, 1);
+	mst->br = br;
+	mst->mstid = mstid;
+	mst->stu.valid = true;
+	mst->stu.sid = *sid;
+	list_add_tail(&mst->node, &chip->msts);
+	return mv88e6xxx_stu_loadpurge(chip, &mst->stu);

I haven't checked what the locking is here - I hope it's not possible
for two of these to run concurrently.

Thanks.

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