If it works in asm, why not use it. There is no problem calling asm from C. I have several drivers (including LCD) written in asm in the days the king of diamonds were still a jack and happily use them again and again instead of reinventing the wheel. I have, however, rewritten a few processes in C because the logic was not readily understandable and it made modification difficult, but that can not apply to something 'straight' like a LCD driver.

Erik