libmlx4 is a userspace driver for Mellanox ConnectX InfiniBand HCAs. It is a plug-in module for libibverbs that allows programs to use Mellanox hardware directly from userspace. See the libibverbs package for more information.
Development sources of libmlx4 are managed with git.
The "official" upstream git tree for libmlx4 is git://git.kernel.org/pub/scm/libs/infiniband/libmlx4.git
The OFED git tree for libmlx4 is git://git.openfabrics.org/ofed_1_5/libmlx4.git