One way auto redirect

In many cases one would only want detection and auto redirect when visiting a site from a mobile device. Meanwhile I expect to not be redirected to desktop version when I visit the mobile version from a desktop.

The case of facebook is an example. Going to www.facebook.com from a mobile device takes you to m.facebook.com and from there you can still force a desktop version of the site. But going to m.facebook.com from a desktop browser does not switch you to www.facebook.com

Could there be an option where we set auto redirect to be one way only? Or could there be two auto-redirect checkboxes:
[ ] Auto detect and redirect to mobile version
[ ] Auto detect and redirect to desktop version