[PATCH net-next] devlink: Add devlink port documentation

[Parav Pandit <parav@nvidia.com>]

Added documentation for devlink port and port function related commands.

Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
---
 .../networking/devlink/devlink-port.rst       | 102 ++++++++++++++++++
 Documentation/networking/devlink/index.rst    |   1 +
 2 files changed, 103 insertions(+)
 create mode 100644 Documentation/networking/devlink/devlink-port.rst

diff --git a/Documentation/networking/devlink/devlink-port.rst b/Documentation/networking/devlink/devlink-port.rst
new file mode 100644
index 000000000000..966d2ee328a6
--- /dev/null
+++ b/Documentation/networking/devlink/devlink-port.rst
@@ -0,0 +1,102 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+============
+Devlink Port
+============
+
+``devlink-port`` provides capability for a driver to expose various
+flavours of ports which exist on device. A devlink port can of an
+embedded switch (eswitch) present on the device.
+
+A devlink port can be of 3 diffferent types.
+
+.. list-table:: List of devlink port types
+   :widths: 23 90
+
+   * - Type
+     - Description
+   * - ``DEVLINK_PORT_TYPE_ETH``
+     - This type is set for a devlink port when a physical link layer of the port
+       is Ethernet.
+   * - ``DEVLINK_PORT_TYPE_IB``
+     - This type is set for a devlink port when a physical link layer of the port
+       is InfiniBand.
+   * - ``DEVLINK_PORT_TYPE_AUTO``
+     - This type is indicated by the user when user prefers to set the port type
+       to be automatically detected by the device driver.
+
+Devlink port can be of few different flavours described below.
+
+.. list-table:: List of devlink port flavours
+   :widths: 33 90
+
+   * - Flavour
+     - Description
+   * - ``DEVLINK_PORT_FLAVOUR_PHYSICAL``
+     - Any kind of port which is physically facing the user. This can be
+       a eswitch physical port or any other physical port on the device.
+   * - ``DEVLINK_PORT_FLAVOUR_CPU``
+     - This indicates a CPU port.
+   * - ``DEVLINK_PORT_FLAVOUR_DSA``
+     - This indicates a interconnect port in a distributed switch architecture.
+   * - ``DEVLINK_PORT_FLAVOUR_PCI_PF``
+     - This indicates an eswitch port representing PCI physical function(PF).
+   * - ``DEVLINK_PORT_FLAVOUR_PCI_VF``
+     - This indicates an eswitch port representing PCI virtual function(VF).
+   * - ``DEVLINK_PORT_FLAVOUR_VIRTUAL``
+     - This indicates a virtual port facing the user.
+   * - ``DEVLINK_PORT_FLAVOUR_VIRTUAL``
+     - This indicates an virtual port facing the user.
+
+A devlink port may be for a controller consist of one or more PCI device(s).
+A devlink instance holds ports of two types of controllers.
+
+(1) controller discovered on same system where eswitch resides
+This is the case where PCI PF/VF of a controller and devlink eswitch
+instance both are located on a single system.
+
+(2) controller located on external host system.
+This is the case where a controller is located in one system and its
+devlink eswitch ports are located in a different system.
+
+An example view of two controller systems::
+
+                 ---------------------------------------------------------
+                 |                                                       |
+                 |           --------- ---------         ------- ------- |
+    -----------  |           | vf(s) | | sf(s) |         |vf(s)| |sf(s)| |
+    | server  |  | -------   ----/---- ---/----- ------- ---/--- ---/--- |
+    | pci rc  |=== | pf0 |______/________/       | pf1 |___/_______/     |
+    | connect |  | -------                       -------                 |
+    -----------  |     | controller_num=1 (no eswitch)                   |
+                 ------|--------------------------------------------------
+                 (internal wire)
+                       |
+                 ---------------------------------------------------------
+                 | devlink eswitch ports and reps                        |
+                 | ----------------------------------------------------- |
+                 | |ctrl-0 | ctrl-0 | ctrl-0 | ctrl-0 | ctrl-0 |ctrl-0 | |
+                 | |pf0    | pf0vfN | pf0sfN | pf1    | pf1vfN |pf1sfN | |
+                 | ----------------------------------------------------- |
+                 | |ctrl-1 | ctrl-1 | ctrl-1 | ctrl-1 | ctrl-1 |ctrl-1 | |
+                 | |pf0    | pf0vfN | pf0sfN | pf1    | pf1vfN |pf1sfN | |
+                 | ----------------------------------------------------- |
+                 |                                                       |
+                 |                                                       |
+                 |           --------- ---------         ------- ------- |
+                 |           | vf(s) | | sf(s) |         |vf(s)| |sf(s)| |
+                 | -------   ----/---- ---/----- ------- ---/--- ---/--- |
+                 | | pf0 |______/________/       | pf1 |___/_______/     |
+                 | -------                       -------                 |
+                 |                                                       |
+                 |  local controller_num=0 (eswitch)                     |
+                 ---------------------------------------------------------
+
+Port function configuration
+===========================
+
+When a port flavor is ``DEVLINK_PORT_FLAVOUR_PCI_PF`` or
+``DEVLINK_PORT_FLAVOUR_PCI_VF``, it represents the port of a PCI function.
+A user can configure the port function attributes before enumerating the
+function. For example user may set the hardware address of the function
+represented by the devlink port.
diff --git a/Documentation/networking/devlink/index.rst b/Documentation/networking/devlink/index.rst
index d82874760ae2..aab79667f97b 100644
--- a/Documentation/networking/devlink/index.rst
+++ b/Documentation/networking/devlink/index.rst
@@ -18,6 +18,7 @@ general.
    devlink-info
    devlink-flash
    devlink-params
+   devlink-port
    devlink-region
    devlink-resource
    devlink-reload
-- 
2.26.2