If you need have a playbook that you can dynamically choose the serial, this is a good way:

serial: "{{ ser_count | default('1') }}"

Make default what you want to run as normally using standard serial convention, and then you can pass is ser_count. Great for control from Ansible Tower templates.

From the command line, this is what you would do to run all hosts at once

ansible-playbook -i hosts.commvault patch.yml -e="ser_count=100%"