You can use IEA-128 on linux like a normal modem, It needn't any driver in linux.
        You can configuration for linux like this.
       1. Basic setup
          Excute "modemtool" in control-panel or terminal.
            Select the device (serial port ) to which your modem is connected.
 
       2.    setup use "netcfg" or "kppp" follow this configj
         connect with pc           
            Baud Rate         115200
            Data Bit            8
            Parity check      none
            Stop Bit            1
            Flow control     RTS/CTS
        3. AT commant set.
        
        initialization string      
		  ATB4          Async PPP Sync PPP conversion
                  ATB41         Async to Sync PPP conversion in ML PPP mode, 							compatible with Microsoft ISDN accelerator pack
                  ATB42         Async to Sync PPP conversion in ML-PPP mode with 						Bandwidth on Demand(BOD)
 
        init response           OK
        Dial string             ATD
        connect response        CONNECT
        Busy Response           BUSY
        No Carrier response     NO CARRIER
        No Dialtone response    NO DIALTONE
        Hangup string           ATH
        Hngup response          OK
        Answer string           ATA
        Ring Response           RING
        Answer Response         CONNECT
        Escape string           +++
        Escape response         OK