1 files changed, 50 insertions, 10 deletions

diff --git a/net/dsa/tag_8021q.c b/net/dsa/tag_8021q.c
index 4adec6bbfe59..65a35e976d7b 100644
--- a/net/dsa/tag_8021q.c
+++ b/net/dsa/tag_8021q.c
@@ -11,20 +11,59 @@
 
 #include "dsa_priv.h"
 
-/* Allocating two VLAN tags per port - one for the RX VID and
- * the other for the TX VID - see below
+/* Binary structure of the fake 12-bit VID field (when the TPID is
+ * ETH_P_DSA_8021Q):
+ *
+ * | 11  | 10  |  9  |  8  |  7  |  6  |  5  |  4  |  3  |  2  |  1  |  0  |
+ * +-----------+-----+-----------------+-----------+-----------------------+
+ * |    DIR    | RSV |    SWITCH_ID    |    RSV    |          PORT         |
+ * +-----------+-----+-----------------+-----------+-----------------------+
+ *
+ * DIR - VID[11:10]:
+ *      Direction flags.
+ *      * 1 (0b01) for RX VLAN,
+ *      * 2 (0b10) for TX VLAN.
+ *      These values make the special VIDs of 0, 1 and 4095 to be left
+ *      unused by this coding scheme.
+ *
+ * RSV - VID[9]:
+ *      To be used for further expansion of SWITCH_ID or for other purposes.
+ *
+ * SWITCH_ID - VID[8:6]:
+ *      Index of switch within DSA tree. Must be between 0 and
+ *      DSA_MAX_SWITCHES - 1.
+ *
+ * RSV - VID[5:4]:
+ *      To be used for further expansion of PORT or for other purposes.
+ *
+ * PORT - VID[3:0]:
+ *      Index of switch port. Must be between 0 and DSA_MAX_PORTS - 1.
  */
-#define DSA_8021Q_VID_RANGE     (DSA_MAX_SWITCHES * DSA_MAX_PORTS)
-#define DSA_8021Q_VID_BASE      (VLAN_N_VID - 2 * DSA_8021Q_VID_RANGE - 1)
-#define DSA_8021Q_RX_VID_BASE   (DSA_8021Q_VID_BASE)
-#define DSA_8021Q_TX_VID_BASE   (DSA_8021Q_VID_BASE + DSA_8021Q_VID_RANGE)
+
+#define DSA_8021Q_DIR_SHIFT             10
+#define DSA_8021Q_DIR_MASK              GENMASK(11, 10)
+#define DSA_8021Q_DIR(x)                (((x) << DSA_8021Q_DIR_SHIFT) & \
+                                                 DSA_8021Q_DIR_MASK)
+#define DSA_8021Q_DIR_RX                DSA_8021Q_DIR(1)
+#define DSA_8021Q_DIR_TX                DSA_8021Q_DIR(2)
+
+#define DSA_8021Q_SWITCH_ID_SHIFT       6
+#define DSA_8021Q_SWITCH_ID_MASK        GENMASK(8, 6)
+#define DSA_8021Q_SWITCH_ID(x)          (((x) << DSA_8021Q_SWITCH_ID_SHIFT) & \
+                                                 DSA_8021Q_SWITCH_ID_MASK)
+
+#define DSA_8021Q_PORT_SHIFT            0
+#define DSA_8021Q_PORT_MASK             GENMASK(3, 0)
+#define DSA_8021Q_PORT(x)               (((x) << DSA_8021Q_PORT_SHIFT) & \
+                                                 DSA_8021Q_PORT_MASK)
 
 /* Returns the VID to be inserted into the frame from xmit for switch steering
  * instructions on egress. Encodes switch ID and port ID.
  */
 u16 dsa_8021q_tx_vid(struct dsa_switch *ds, int port)
 {
-        return DSA_8021Q_TX_VID_BASE + (DSA_MAX_PORTS * ds->index) + port;
+        return DSA_8021Q_DIR_TX | DSA_8021Q_SWITCH_ID(ds->index) |
+               DSA_8021Q_PORT(port);
 }
 EXPORT_SYMBOL_GPL(dsa_8021q_tx_vid);
 
@@ -33,21 +72,22 @@ EXPORT_SYMBOL_GPL(dsa_8021q_tx_vid);
  */
 u16 dsa_8021q_rx_vid(struct dsa_switch *ds, int port)
 {
-        return DSA_8021Q_RX_VID_BASE + (DSA_MAX_PORTS * ds->index) + port;
+        return DSA_8021Q_DIR_RX | DSA_8021Q_SWITCH_ID(ds->index) |
+               DSA_8021Q_PORT(port);
 }
 EXPORT_SYMBOL_GPL(dsa_8021q_rx_vid);
 
 /* Returns the decoded switch ID from the RX VID. */
 int dsa_8021q_rx_switch_id(u16 vid)
 {
-        return ((vid - DSA_8021Q_RX_VID_BASE) / DSA_MAX_PORTS);
+        return (vid & DSA_8021Q_SWITCH_ID_MASK) >> DSA_8021Q_SWITCH_ID_SHIFT;
 }
 EXPORT_SYMBOL_GPL(dsa_8021q_rx_switch_id);
 
 /* Returns the decoded port ID from the RX VID. */
 int dsa_8021q_rx_source_port(u16 vid)
 {
-        return ((vid - DSA_8021Q_RX_VID_BASE) % DSA_MAX_PORTS);
+        return (vid & DSA_8021Q_PORT_MASK) >> DSA_8021Q_PORT_SHIFT;
 }
 EXPORT_SYMBOL_GPL(dsa_8021q_rx_source_port);