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chromium / chromiumos / third_party / hdctools / HEAD / . / servo / interface
tree: 5fdc7e1d4a7bb3828ce115cd74a790fee28c2b64 [path history] [tgz]
  1. __init__.py
  2. common.py
  3. ec3po_interface.py
  4. empty.py
  5. ftdi_common.py
  6. ftdi_utils.py
  7. ftdii2c.py
  8. ftdiuart.py
  9. gpio_interface.py
  10. i2c_base.py
  11. i2cbus.py
  12. interface.py
  13. Makefile
  14. README.md
  15. stm32gpio.py
  16. stm32i2c.py
  17. stm32uart.py
  18. stm32usb.py
  19. uart.py
servo/interface/README.md

Introduction

A servo interface (effectively) maps to a usb end-point on a servo device that can perform a certain task. More generally, the idea is that a servo device supports multiple interfaces to perform multiple separate tasks. So far, we support GPIO, I2C, and UART interfaces. This short README is designed to give an overview of the servo.interface module.

Overview

Recall that a servo device is one usb device with a collection of interfaces. Depending on the device, there are different interfaces. These interfaces are implemented in this module. The module itself provides a ‘clean’ discovery method that allows the interface writers to identify their interface with a ‘name’ static method, and the servo_interfaces.py list (that maps servo devices to a list of interfaces and parameters on how to build them). So adding a new interface happens here, while describing how to build and deploy that interface on a new servo device happens in servo_interfaces.py.

Lastly, consider an example like ec3po: this is an entirely software interface that takes an underlying “real” interface and provide functionality on top of that. This means that an interface can also be developed by adding functionality on top of a current interface.

defining Build()

Build is invoked from the servo_server with keyword arguments only. It gets invoked with the union of all arguments that any known Build implementation needs. This means that some Build() implementations do not require the passed in arguments. It's fine to either ignore them (and mark so for pylint) or leverage |kwargs|.

In its current implemenation Build is invoked with the following parameters:

  • index: the interface index i.e. whether it's the first, second, or 10th
  • vid, pid, serial: the identifiers for the underlying device
  • interface_data: a (custom) dictionary with extra data to build the interface. This is taken directory from servo_interfaces.py and passed to the Build() function.
  • servod: a reference to servod for interfaces that need to query information about the system to build themselves e.g. ec3po