We currently use the atomic openshift installer to install OCP, which generates an ansible hosts file based on the input cfg file we generate as part of the cluster infrastructure creation. This appears to still work when setting the deployment type to "origin" and changing the ansible playbook path to one where the ansible-playbook repo has been cloned at the correct origin tag.

atomic-openshift-installer --unattended --configuration #{installer_cfg_file} --ansible-playbook-directory #{playbook_dir} install --force

It might be better in the longer term to just bypass the atomic openshift installer entirely and call the ansible playbooks directly, but since the installer generates a valid host file for us, and everything is there to configure it as required, it will be the quickest solution to installing origin vs ocp to just keep using it for now.