device: init module, add UnblockDevice, BlockDevice

tower: https://tower.im/projects/8f19f0bf0e754f0b82ef2c24bc230973/todos/b36ee8058e7d4756816f70a0dd8290f8/
Change-Id: If0bb4600e6129e1a4ad1a270b2ca94c7614df37d