Greybus Simulator (gbsim)

A tool which simulates an AP Bridge, SVC, and an arbitrary set of Ara modules plugged into Greybus.

Provided under BSD license. See LICENSE for details.

Quick Start

This code depends on header files present in the "greybus" source directory. The location of this directory is defined in the GBDIR environment variable.

To just build gbsim, do this:

export GBDIR=".../path/to/greybus"
./autogen.sh
./configure
make

Install

The easiest path to get started is to run the kernel greybus support and gbsim on the same machine. This is accomplished using the dummy_hcd USB host+gadget driver in conjuction with the gadget configfs/functionfs features.

Set the environment variable GBDIR to point at the kernel greybus (https://github.com/gregkh/greybus) directory as the simulator shares headers with the kernel code.

export GBDIR=".../path/to/greybus"

Build the kernel greybus subsystem, including the host driver and related protocol drivers.

cd "${GBDIR}"
make -C /usr/src/linux-headers-foo M=$PWD
make -C /usr/src/linux-headers-foo M=$PWD modules_install

Build it:

gbsim has the following dependencies:

• libusbg (https://github.com/libusbg/libusbg)
• libconfig (http://hyperrealm.com/libconfig/libconfig.html)
• libsoc (https://github.com/jackmitch/libsoc)

It also assumes the GBDIR environment variable has been set.

cd /path/to/gbsim
./autogen.sh
./configure
make
make install

If you would like to cross-compile the simulator, you can optionally specify the prefix used for compilation tools at configure time. For example:

./configure --host=arm-linux-gnueabi

If your build environment only supplies the legacy (pre-V2) USB descriptor format, you can indicate that when configuring as well:

./configure --enable-legacy-descriptors

(If you get errors about FUNCTIONFS_DESCRIPTORS_MAGIC_V2 not being defined, you'll need this.)

Run

Load up the greybus framework and ES1 USB driver:

modprobe greybus
modprobe gb-es1
modprobe gb-phy

Now start the simulator:

modprobe configfs
mount -t configfs none /sys/kernel/config
modprobe libcomposite
modprobe dummy_hcd
gbsim -h /path/to -v

Where /path/to is the base directory containing the directory hotplug-modules

gbsim supports the following option flags:

• -b: enable the BeagleBone Black hardware backend
• -h: hotplug base directory
• -i: i2c adapter (if BBB hardware backend is enabled)
• -v: enable verbose output

Using the simulator

After running output should appear as follows:

[I] GBSIM: gbsim gadget created
[D] GBSIM: event BIND,0
[D] GBSIM: event ENABLE,2
[D] GBSIM: Start SVC/CPort endpoints
[D] GBSIM: SVC->AP handshake sent
[D] GBSIM: event SETUP,4
[D] GBSIM: AP->AP Bridge setup message:
[D] GBSIM:   bRequestType = 41
[D] GBSIM:   bRequest     = 01
[D] GBSIM:   wValue       = 0000
[D] GBSIM:   wIndex       = 0000
[D] GBSIM:   wLength      = 000b
[D] GBSIM: AP->SVC message:
  00 00 03 00 00 01 01 00 00 00 00 
[I] GBSIM: AP handshake complete

This indicates that the simulated AP Bridge device was enumerated by the host, a handshake message was sent to the AP, and another handshake message received from the AP indicating that the handshake process has completed.

At this point, it's possible to hot plug/unplug modules by simply copying or removing a conformant manifest blob file in the /path/to/hotplug-module directory. Manifest blob files can be created using the Manifesto tool found at https://github.com/projectara/manifesto. Using the Simple I2C Module as an example, a module can be inserted as follows:

cp /foo/bar/simple-i2c-module.mnfb /path/to/hotplug-module/simple-i2c-module.mnfb

After module insertion, gbsim will report:

[I] GBSIM: simple-i2c-module.mnfb module inserted
[D] GBSIM: SVC->AP hotplug event (plug) sent