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2224fb8b1d
The option:: doesn't render properly, follow the example of the other devices. Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
99 lines
3.0 KiB
Markdown
99 lines
3.0 KiB
Markdown
# vhost-device-gpio - GPIO emulation backend daemon
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## Description
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This program is a vhost-user backend that emulates a VirtIO GPIO device. This
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program takes a list of gpio devices on the host OS and then talks to them via
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the /dev/gpiochip{X} interface when a request comes from the guest OS for an
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GPIO device.
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This program is tested with QEMU's `-device vhost-user-gpio-pci` but should
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work with any virtual machine monitor (VMM) that supports vhost-user. See the
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Examples section below.
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## Synopsis
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```shell
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vhost-device-gpio [OPTIONS] --socket-path <SOCKET_PATH> --device-list <DEVICE_LIST>
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```
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## Options
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```text
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vhost-device-gpio
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-h, --help
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Print help.
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-s, --socket-path=PATH
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Location of vhost-user Unix domain sockets, this path will be suffixed with
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0,1,2..socket_count-1.
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-c, --socket-count=INT
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Number of guests (sockets) to attach to, default set to 1.
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-l, --device-list=GPIO-DEVICES
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GPIO device list at the host OS in the format:
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<device1>[:<device2>]
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Example: --device-list "2:4:7"
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Here, each GPIO devices correspond to a separate guest instance, i.e. the
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number of devices in the device-list must match the number of sockets in the
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--socket-count. For example, the GPIO device 0 will be allocated to the guest
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with "<socket-path>0" path.
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```
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## MockGpioDevice support
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As connecting VM guests to random GPIO pins on your host is generally
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asking for trouble you can enable the "mock_gpio" feature in your build:
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cargo build --features "mock_gpio"
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You can then enable simulated GPIOs using the 's' prefix:
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--device-list s4:s8
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Which will create two gpio devices, the first with 4 pins and the
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second with 8. By default updates are display via env logger:
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vhost-device-gpio -s /tmp/vus.sock -c 1 -l s4
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[2023-09-14T14:15:14Z INFO vhost_device_gpio::mock_gpio] gpio dummy0 set value to 1
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[2023-09-14T14:15:14Z INFO vhost_device_gpio::mock_gpio] gpio dummy0 set direction to 1
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[2023-09-14T14:15:14Z INFO vhost_device_gpio::mock_gpio] gpio dummy0 set direction to 0
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[2023-09-14T14:15:19Z INFO vhost_device_gpio::mock_gpio] gpio dummy1 set value to 1
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[2023-09-14T14:15:19Z INFO vhost_device_gpio::mock_gpio] gpio dummy1 set direction to 1
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[2023-09-14T14:15:19Z INFO vhost_device_gpio::mock_gpio] gpio dummy1 set direction to 0
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## Examples
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The daemon should be started first:
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::
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host# vhost-device-gpio --socket-path=gpio.sock --socket-count=2 --device-list 0:3
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The QEMU invocation needs to create a chardev socket the device can
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use to communicate as well as share the guests memory over a memfd.
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::
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host# qemu-system \
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-chardev socket,path=vgpio.sock,id=vgpio \
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-device vhost-user-gpio-pci,chardev=vgpio,id=gpio \
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-m 4096 \
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-object memory-backend-file,id=mem,size=4G,mem-path=/dev/shm,share=on \
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-numa node,memdev=mem \
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...
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## License
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This project is licensed under either of
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- [Apache License](http://www.apache.org/licenses/LICENSE-2.0), Version 2.0
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- [BSD-3-Clause License](https://opensource.org/licenses/BSD-3-Clause)
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