[PATCH 4/5] docs: add a man page for vhost-user-i2c

[Viresh Kumar <viresh.kumar@linaro.org>]

Basic usage and example invocation.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 docs/tools/index.rst          |  1 +
 docs/tools/vhost-user-i2c.rst | 75 +++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+)
 create mode 100644 docs/tools/vhost-user-i2c.rst

diff --git a/docs/tools/index.rst b/docs/tools/index.rst
index 3a5829c17a54..af2519406ddf 100644
--- a/docs/tools/index.rst
+++ b/docs/tools/index.rst
@@ -17,3 +17,4 @@ QEMU Tools Guide
    qemu-trace-stap
    virtfs-proxy-helper
    virtiofsd
+   vhost-user-i2c
diff --git a/docs/tools/vhost-user-i2c.rst b/docs/tools/vhost-user-i2c.rst
new file mode 100644
index 000000000000..8471b39d8b1d
--- /dev/null
+++ b/docs/tools/vhost-user-i2c.rst
@@ -0,0 +1,75 @@
+QEMU vhost-user-i2c - I2C emulation backend
+===========================================
+
+Synopsis
+--------
+
+**vhost-user-i2c** [*OPTIONS*]
+
+Description
+-----------
+
+This program is a vhost-user backend that emulates a VirtIO I2C bus.
+This program takes the layout of the i2c bus and its devices on the host
+OS and then talks to them via the /dev/i2c-X interface when a request
+comes from the guest OS for an I2C device.
+
+This program is designed to work with QEMU's ``-device
+vhost-user-i2c-pci`` but should work with any virtual machine monitor
+(VMM) that supports vhost-user. See the Examples section below.
+
+Options
+-------
+
+.. program:: vhost-user-i2c
+
+.. option:: -h, --help
+
+  Print help.
+
+.. option:: -v, --verbose
+
+   Increase verbosity of output
+
+.. option:: -s, --socket-path=PATH
+
+  Listen on vhost-user UNIX domain socket at PATH. Incompatible with --fd.
+
+.. option:: -f, --fd=FDNUM
+
+  Accept connections from vhost-user UNIX domain socket file descriptor FDNUM.
+  The file descriptor must already be listening for connections.
+  Incompatible with --socket-path.
+
+.. option:: -l, --device-list=I2C-DEVICES
+
+  I2c device list at the host OS in the format:
+      <bus>:<client_addr>[:<client_addr>],[<bus>:<client_addr>[:<client_addr>]]
+
+      Example: --device-list "2:1c:20,3:10:2c"
+
+  Here,
+      bus (decimal): adatper bus number. e.g. 2 for /dev/i2c-2, 3 for /dev/i2c-3.
+      client_addr (hex): address for client device. e.g. 0x1C, 0x20, 0x10, 0x2C.
+
+Examples
+--------
+
+The daemon should be started first:
+
+::
+
+  host# vhost-user-i2c --socket-path=vi2c.sock --device-list 0:20
+
+The QEMU invocation needs to create a chardev socket the device can
+use to communicate as well as share the guests memory over a memfd.
+
+::
+
+  host# qemu-system \
+      -chardev socket,path=vi2c.sock,id=vi2c \
+      -device vhost-user-i2c-pci,chardev=vi2c,id=i2c \
+      -m 4096 \
+      -object memory-backend-file,id=mem,size=4G,mem-path=/dev/shm,share=on \
+      -numa node,memdev=mem \
+      ...
-- 
2.25.0.rc1.19.g042ed3e048af