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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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.