On Sat, Jan 24, 2026 at 01:47:59AM +0200, Vladimir Oltean wrote:

quoted

+static int
+yt921x_dsa_port_del_dscp_prio(struct dsa_switch *ds, int port, u8 dscp, u8 prio)
+{
+	struct yt921x_priv *priv = to_yt921x_priv(ds);
+	int res;
+
+	mutex_lock(&priv->reg_lock);
+	res = yt921x_reg_write(priv, YT921X_IPM_DSCPn(dscp),
+			       ipm_ctrl(IEEE8021Q_TT_BK));

Question regarding semantics, also for Oleksij: deleting the DSCP app
table entry should cause that DSCP value to be mapped to bulk, as in
your interpretation (or best effort for KSZ), or according to the next
selector in line, as per trust order (for example port default priority,
which may not be bulk)?

It maps to bulk.

My interpretation of this hardware is that it uses a direct lookup table
without a "valid/invalid" bit per entry. Once DSCP is enabled in the
trust order, the switch performs the lookup for every packet; it cannot
transparently skip a specific DSCP value to fall back to the next
selector.

Therefore, "deleting" an entry practically remaps it to the default
(Bulk/Best Effort) priority. This matches the logic we use in the KSZ
driver.

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