Virtual USB Printer

Virtual USB Printer provides a server which can be used with USBIP in order to emulate a USB printing device and bind it to the system as if it were physically connected to a USB port.

Virtual USB Printer supports both regular USB printers as well as IPP-over-USB devices.

Motivation

This project was created in order to make on-device tests which check for any regressions in the native USB printing system.

Installation

As of https://crrev.com/c/3093381, virtual-usb-printer is built and installed by default on all test images that support it.

If for some reason you need to build it yourself, you can USE=usbip when building packages for your board - i.e.

USE="usbip" ./build_packages --board=$BOARD

How to Use

For ease of human operation, start virtual-usb-printer via its Upstart unit. Pass the appropriate arguments to the invocation as needed.

For example, to start and connect the virtual-usb-printer as an IPP-over-USB printer, issue

start virtual-usb-printer USB_DESCRIPTORS=ippusb_printer.json IPP_ATTRIBUTES=ipp_attributes.json

Consult the Upstart config file to see the arguments understood in this context.

Configuration

The printer's USB descriptors and defined IPP attributes can be configured using a JSON file and are loaded at run-time using command line flags. Example configurations can be found in the config/ directory.

The configuration files can be loaded with the following flags:

• --descriptors_path - full path to the JSON file which defines the USB descriptors
• --attributes_path - full path to the JSON file which defines the supported IPP attributes
  • Only needed for IPP-over-USB printer configurations
• --record_doc_path - full path to the file used to record documents received from print jobs
• --output_log_dir - directory path specifying where scan settings will be logged

Using in Tast

Refer to these existing tast tests for examples of how to use the virtual-usb-printer to test the Chromium OS printing stack.

Print Tests

• printer.AddUSBPrinter
  • Tests that adding a basic USB printer works correctly
• printer.PrintUSB
  • Tests that the full print pipeline works correctly for a basic USB printer
• printer.PrintIPPUSB
  • Tests that the full print pipeline for IPP-over-USB printing works correctly
  • This also tests that the automatic_usb_printer_configurer is able to automatically configure an IPP Everywhere printer
• printer.IPPUSBPPDNoCopies, printer.IPPUSBPPDCopiesUnsupported, and printer.IPPUSBPPDCopiesSupported
  • Tests that the CUPS understands whether or not printers support print job copies (duplication).

Scan Tests

• documentscanapi.Scan
  • Tests the document scanner app.
• scanner.EnumerateIPPUSB
  • Tests that lorgnette can correctly enumerate IPP USB devices.
• scanner.ScanESCLIPP
  • Tests basic scanning functionality via IPP USB.