+ if (!cmd->t_data_nents)
+ return NULL;
+ else if (cmd->t_data_nents == 1)
+ return kmap(sg_page(sg)) + sg->offset;
+
+ /* >1 page. use vmap */
+ pages = kmalloc(sizeof(*pages) * cmd->t_data_nents, GFP_KERNEL);
+ if (!pages)
+ return NULL;
+
+ /* convert sg[] to pages[] */
+ for_each_sg(cmd->t_data_sg, sg, cmd->t_data_nents, i) {
+ pages[i] = sg_page(sg);
+ }
+
+ cmd->t_data_vmap = vmap(pages, cmd->t_data_nents, VM_MAP, PAGE_KERNEL);
+ kfree(pages);
+ if (!cmd->t_data_vmap)
+ return NULL;
+
+ return cmd->t_data_vmap + cmd->t_data_sg[0].offset;