i_cdev
file->device = container_of(inode->i_cdev->si_drv1, struct ib_ucm_device, cdev);
port = container_of(inode->i_cdev->si_drv1, struct ib_umad_port, sm_cdev);
port = container_of(inode->i_cdev->si_drv1, struct ib_umad_port, cdev);
dev = container_of(inode->i_cdev->si_drv1, struct ib_uverbs_device, cdev);