After much trial and tribulation, we found out that the cards ship by default with the infiniband protocol enabled (IB). We (MAAS) needs it to be configured as ETH protocol. So in order to do that automatically on comissioning, you should download the latest mellanox MFT tool: http://www.mellanox.com/page/management_tools
and then use this as a commissioning script, named 00-maas-00-mftinstall.sh:
you’ll have to host the .tgz file somewhere and update the script to download it from whatever URL you use.
This script will install the Mellanox mangement tools, and then set the firmware on your card to be ETH. After the machine commissions, you’ll be able to configure your mellanox 100G cards in MAAS.