Since you are already modifying this code, I would just use bool here (because it's shorter).

All of the above should be size_t, and constified AFAICT (or at least const unsigned int).

Adding this padding here is very ugly. Shouldn't the padding be added by hv_ring_buffer_write automatically? It seems open-coding this for every caller of hv_ring_buffer_write is very inefficient.

return (error);