vhost-device/gpio

vhost-device-gpio - GPIO emulation backend daemon

Description

This program is a vhost-user backend that emulates a VirtIO GPIO device. This program takes a list of gpio devices on the host OS and then talks to them via the /dev/gpiochip{X} interface when a request comes from the guest OS for an GPIO device.

This program is tested with QEMU's -device vhost-user-gpio-pci but should work with any virtual machine monitor (VMM) that supports vhost-user. See the Examples section below.

Synopsis

vhost-device-gpio [OPTIONS]

Options

.. program:: vhost-device-gpio

.. option:: -h, --help

Print help.

.. option:: -s, --socket-path=PATH

Location of vhost-user Unix domain sockets, this path will be suffixed with 0,1,2..socket_count-1.

.. option:: -c, --socket-count=INT

Number of guests (sockets) to attach to, default set to 1.

.. option:: -l, --device-list=GPIO-DEVICES

GPIO device list at the host OS in the format: [:]

  Example: --device-list "2:4:7"

Here, each GPIO devices correspond to a separate guest instance, i.e. the number of devices in the device-list must match the number of sockets in the --socket-count. For example, the GPIO device 0 will be allocated to the guest with "0" path.

Examples

The daemon should be started first:

::

host# vhost-device-gpio --socket-path=gpio.sock --socket-count=1 --device-list 0:3

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=vgpio.sock,id=vgpio
-device vhost-user-gpio-pci,chardev=vgpio,id=gpio
-m 4096
-object memory-backend-file,id=mem,size=4G,mem-path=/dev/shm,share=on
-numa node,memdev=mem
...