MarsSeed [1] filed a deletion request for cm256cc-git [2]: Unmaintained, badly packaged VCS build from 2017, and master branch code is exactly the same as what extra repo's cm256cc uses.
Which makes this PKGBUILD an inferiorly configured duplicate - one that is superfluous. [1] https://aur.archlinux.org/account/MarsSeed/ [2] https://aur.archlinux.org/pkgbase/cm256cc-git/
