amdiommu_ir_find
ctx = amdiommu_ir_find(src, &rid, &is_iommu);
ctx = amdiommu_ir_find(src, NULL, NULL);
static struct amdiommu_ctx *amdiommu_ir_find(device_t src, uint16_t *rid,
ctx = amdiommu_ir_find(src, NULL, NULL);