An experimental version of the linux usbtmc kernel driver has been released at https://github.com/dpenkler/linux-usbtmcfor folks to test and suggest new features before having them submitted to the upstream kernel.
The current version of the driver has some additional capabilities that have not yet been submitted upstream. These include module parameters to configure the buffer size and usb timeout and also an ioctl to send a device trigger.
The build and resulting driver have been tested successfully on "3.16.0-4-amd64 #1 SMP Debian 3.16.39-1+deb8u2" and a stock kernel.org 4.11.3, so should build OK on the intervening kernel versions.
Please see the README of the project for more details.