In this paper, the problem of control allocation is revisited focusing on weakly redundant plants, that is plants having more inputs than outputs but such that no input can be equivalently substituted by a combination of the others. Considering the case of asymptotically constant references, it is shown that input allocation can be used to optimize the steady state input, without altering (even during transients) the output response induced by any a priori given controller. Moreover, a general structure for the allocator is proposed, consisting of a series connection of a steady-state optimizer and an annihilator