vhost-user-i2c - I2C emulation backend daemon

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 or SMBUS device.

This program is tested 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.

Synopsis

vhost-user-i2c [OPTIONS]

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: :[:],[:[:]]

  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 \ ...