msm_rbmemptrs
memptrs += sizeof(struct msm_rbmemptrs);
memptrs_iova += sizeof(struct msm_rbmemptrs);
sizeof(struct msm_rbmemptrs) * nr_rings,
struct msm_rbmemptrs *memptrs = gpu->rb[0]->memptrs;
((ring)->memptrs_iova + offsetof(struct msm_rbmemptrs, member))
struct msm_rbmemptrs *memptrs;