return retval;
 }
 
-static int default_virt2phys(struct target_s *target, uint32_t virtual, uint32_t *physical)
+static int identity_virt2phys(struct target_s *target,
+               uint32_t virtual, uint32_t *physical)
 {
        *physical = virtual;
        return ERROR_OK;
 }
 
-static int default_mmu(struct target_s *target, int *enabled)
+static int no_mmu(struct target_s *target, int *enabled)
 {
        *enabled = 0;
        return ERROR_OK;
 }
 
 static int
-default_read_phys_memory(struct target_s *target, uint32_t address,
+err_read_phys_memory(struct target_s *target, uint32_t address,
                uint32_t size, uint32_t count, uint8_t *buffer)
 {
        LOG_ERROR("Not implemented: %s", __func__);
 }
 
 static int
-default_write_phys_memory(struct target_s *target, uint32_t address,
+err_write_phys_memory(struct target_s *target, uint32_t address,
                uint32_t size, uint32_t count, uint8_t *buffer)
 {
        LOG_ERROR("Not implemented: %s", __func__);
                /* Set up default functions if none are provided by target */
                if (target->type->virt2phys == NULL)
                {
-                       target->type->virt2phys = default_virt2phys;
+                       target->type->virt2phys = identity_virt2phys;
                }
 
                if (target->type->read_phys_memory == NULL)
                {
-                       target->type->read_phys_memory = default_read_phys_memory;
+                       target->type->read_phys_memory = err_read_phys_memory;
                }
 
                if (target->type->write_phys_memory == NULL)
                {
-                       target->type->write_phys_memory = default_write_phys_memory;
+                       target->type->write_phys_memory = err_write_phys_memory;
                }
 
+               /**
+                * @todo MCR/MRC are ARM-specific; don't require them in
+                * all targets, or for ARMs without coprocessors.
+                */
                if (target->type->mcr == NULL)
                {
                        target->type->mcr = default_mcr;
                }
 
 
+               /**
+                * @todo get rid of those *memory_imp() methods, now that all
+                * callers are using target_*_memory() accessors ... and make
+                * sure the "physical" paths handle the same issues.
+                */
+
                /* a non-invasive way(in terms of patches) to add some code that
                 * runs before the type->write/read_memory implementation
                 */
 
                if (target->type->mmu == NULL)
                {
-                       target->type->mmu = default_mmu;
+                       target->type->mmu = no_mmu;
                }
                target = target->next;
        }
                        "loads active fast load image to current target "
                        "- mainly for profiling purposes");
 
-
+       /** @todo don't register virt2phys() unless target supports it */
        register_command(cmd_ctx, NULL, "virt2phys",
                        handle_virt2phys_command, COMMAND_ANY,
                        "translate a virtual address into a physical address");
+
        register_command(cmd_ctx,  NULL, "reg",
                        handle_reg_command, COMMAND_EXEC,
                        "display or set a register");