arm_smmu_invs_alloc
test_a = arm_smmu_invs_alloc(0);
new_invs = arm_smmu_invs_alloc(num_invs);
new_invs = arm_smmu_invs_alloc(invs->num_invs - invs->num_trashes);
new_invs = arm_smmu_invs_alloc(0);
master->build_invs = arm_smmu_invs_alloc(2);
master->build_invs = arm_smmu_invs_alloc(2 + fwspec->num_ids);