Someone

 switch (*d) {
                                        case '1':
                                                switch_set_flag(ep, ED_MUX_READ);
                                                switch_clear_flag(ep, ED_MUX_WRITE);
                                                break;
                                        case '2':
                                                switch_set_flag(ep, ED_MUX_WRITE);
                                                switch_clear_flag(ep, ED_MUX_READ);
                                                break;
                                        case '3':
                                                switch_set_flag(ep, ED_MUX_READ);
                                                switch_set_flag(ep, ED_MUX_WRITE);
                                                break;
                                        case '4':
                                                return status; 
                                        case '0':
                                                switch_clear_flag(ep, ED_MUX_READ);
                                                switch_clear_flag(ep, ED_MUX_WRITE);
                                                break;
                                        default:
                                                z = 0;
                                                break;

                                        }