Linux IOCTLs for USB2Serial

Question

I'm developing a program in C++ on Linux which interacts with a USB2Serial adapter to fetch some information from the remote terminal. I was able to set it the IOCTL on windows using the following code:

 #define IOCTL_SERIAL_XOFF_COUNTER       CTL_CODE(FILE_DEVICE_SERIAL_PORT,28,METHOD_BUFFERED,FILE_ANY_ACCESS)

unsigned char xoff_counter[] = {0xd0,0x07,0x00,0x00,0x05,0x00,0x00,0x00,0x13,0x00,0x00,0x00};

        bool result = DeviceIoControl(file,IOCTL_SERIAL_XOFF_COUNTER,
                                        &xoff_counter, sizeof(xoff_counter),
                                        NULL,0,
                                        &junk,
                                        &o);

I tried doing the same on Linux using the following code:

#define SERIAL_XOFF_COUNTER 28

unsigned char xoff_counter[] = {0xd0,0x07,0x00,0x00,0x05,0x00,0x00,0x00,0x13,0x00,0x00,0x00};

int retVal = ioctl(fd,SERIAL_XOFF_COUNTER,xoff_counter);
            if(retVal < 0){
                cout << "Error while setting ioctl:"<<strerror(errno)<<endl;
            }

This is raising an error when I run the program:

Error while setting ioctl:Inappropriate ioctl for device

If anyone has worked in these ioctls before, please let me know what the Linux equivalents are for this flag.
TIA!

Answer 1

There's no serial ioctl for that in linux. That ioctl is specific of the windows serial driver. XON/XOFF protocol has no counters defined, so I cannot imagine what is this being used for. (perhaps Windows is counting the number of XOFF characters received, but just a speculation)

See termios(3) manual page of linux to see the ioctls defined for rs232 terminal control.