Hi Greg > I didn't see anything obvious, but I just realized, have you tried this > with any other usb to serial device to see if the same thing happens > there or not? I tried using the pl2303.c. I observer the same behavior, i.e. tcgetattr results in a call to ioctl with 0x5401() as command (TCGETS). Does it mean that the mistake is in my testing program ? Here the code snippet opening the USB serial device and the calling tcgetattr. void *TxThread(void *threadid) { long tid; tid = (long)threadid; int fdtx; struct termios oldtermios,newtermios; int retval; printf("TxThread, thread #%ld!\n", tid); // open device fdtx = open( deviceFileName, O_RDWR ); if (fdtx < 0) { CONSOLE("Could not open device '%s'(%d)", deviceFileName,fdtx); retval = EDEVICE; goto tx_exit; } CONSOLE("Device '%s' (%d) opened\n",deviceFileName,fdtx); tcgetattr(fdtx,&oldtermios); /* save current port settings */ .... Tilman -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html