Like all computer hardware, InfiniBand adapters need drivers in order to be used by the operating system. Most modern Linux distributions provide the kernel drivers, libraries, and support programs needed to have a functioning InfiniBand adapter. While functional, these may not be the best choice in all cases.
When a new InfiniBand card, or firmware version is released there may be performance gains available by using the drivers from the Open Fabrics Alliance. These drivers are faster to be released than those included in the Linux kernel and with the Linux distributions.