net: dsa: tag_8021q: support up to 8 VLANs per port using sub-VLANs

For switches that support VLAN retagging, such as sja1105, we extend
dsa_8021q by encoding a "sub-VLAN" into the remaining 3 free bits in the
dsa_8021q tag.

A sub-VLAN is nothing more than a number in the range 0-7, which serves
as an index into a per-port driver lookup table. The sub-VLAN value of
zero means that traffic is untagged (this is also backwards-compatible
with dsa_8021q without retagging).

The switch should be configured to retag VLAN-tagged traffic that gets
transmitted towards the CPU port (and towards the CPU only). Example:

bridge vlan add dev sw1p0 vid 100

The switch retags frames received on port 0, going to the CPU, and
having VID 100, to the VID of 1104 (0x0450). In dsa_8021q language:

 | 11  | 10  |  9  |  8  |  7  |  6  |  5  |  4  |  3  |  2  |  1  |  0  |
 +-----------+-----+-----------------+-----------+-----------------------+
 |    DIR    | SVL |    SWITCH_ID    |  SUBVLAN  |          PORT         |
 +-----------+-----+-----------------+-----------+-----------------------+

0x0450 means:
 - DIR = 0b01: this is an RX VLAN
 - SUBVLAN = 0b001: this is subvlan #1
 - SWITCH_ID = 0b001: this is switch 1 (see the name "sw1p0")
 - PORT = 0b0000: this is port 0 (see the name "sw1p0")

The driver also remembers the "1 -> 100" mapping. In the hotpath, if the
sub-VLAN from the tag encodes a non-untagged frame, this mapping is used
to create a VLAN hwaccel tag, with the value of 100.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 16 insertions, 0 deletions

diff --git a/include/linux/dsa/8021q.h b/include/linux/dsa/8021q.h
index 404bd2cce642..311aa04e7520 100644
--- a/include/linux/dsa/8021q.h
+++ b/include/linux/dsa/8021q.h
@@ -20,6 +20,8 @@ struct dsa_8021q_crosschip_link {
 	refcount_t refcount;
 };
 
+#define DSA_8021Q_N_SUBVLAN			8
+
 #if IS_ENABLED(CONFIG_NET_DSA_TAG_8021Q)
 
 int dsa_port_setup_8021q_tagging(struct dsa_switch *ds, int index,
@@ -42,10 +44,14 @@ u16 dsa_8021q_tx_vid(struct dsa_switch *ds, int port);
 
 u16 dsa_8021q_rx_vid(struct dsa_switch *ds, int port);
 
+u16 dsa_8021q_rx_vid_subvlan(struct dsa_switch *ds, int port, u16 subvlan);
+
 int dsa_8021q_rx_switch_id(u16 vid);
 
 int dsa_8021q_rx_source_port(u16 vid);
 
+u16 dsa_8021q_rx_subvlan(u16 vid);
+
 bool vid_is_dsa_8021q(u16 vid);
 
 #else
@@ -88,6 +94,11 @@ u16 dsa_8021q_rx_vid(struct dsa_switch *ds, int port)
 	return 0;
 }
 
+u16 dsa_8021q_rx_vid_subvlan(struct dsa_switch *ds, int port, u16 subvlan)
+{
+	return 0;
+}
+
 int dsa_8021q_rx_switch_id(u16 vid)
 {
 	return 0;
@@ -98,6 +109,11 @@ int dsa_8021q_rx_source_port(u16 vid)
 	return 0;
 }
 
+u16 dsa_8021q_rx_subvlan(u16 vid)
+{
+	return 0;
+}
+
 bool vid_is_dsa_8021q(u16 vid)
 {
 	return false;