IOCTL on Linux

GeekyNorm · 07-23-2015, 05:11 AM

Hi Folks,
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 the IOCTL_SERIAL_XOFF_COUNTER on windows using the following code:

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:

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:

Code:

Error while setting ioctl:Inappropriate ioctl for device

So if any of you have done something similar before, please let me know how I can map the IOCTLs from my windows program to the corresponding calls on Linux.
TIA! Regards,
Nachiketh

NevemTeve · 07-23-2015, 06:52 AM

In a userspace program, you cannot invent new ioctls (even if they exist in Windows), only use the existing ones. See manuals of termios(3) and stty(1), also this:
http://tldp.org/HOWTO/Serial-Programming-HOWTO/

GeekyNorm · 07-24-2015, 02:21 AM

Quote:

Originally Posted by NevemTeve

In a userspace program, you cannot invent new ioctls (even if they exist in Windows), only use the existing ones. See manuals of termios(3) and stty(1), also this:
http://tldp.org/HOWTO/Serial-Programming-HOWTO/

Hi,
Thanks for the reply.
I did have a look at termios and stty, but I could not find any setting to flags to set the IOCTL_SERIAL_XOFF_COUNTER and also the IOCTL_SERIAL_LSRMST_INSERT control codes in them. Does this mean these cannot be set on Linux? Please let me know.
Thanks & Regards,
Nachiketh

NevemTeve · 07-24-2015, 02:56 AM

I think it depends on what are they supposed to do.

GeekyNorm · 07-24-2015, 03:03 AM

Quote:

Originally Posted by NevemTeve

I think it depends on what are they supposed to do.

According to the MSDN documentation:

Quote:

IOCTL_SERIAL_LSRMST_INSERT Enables or disables the placement of line status and modem status values into the regular data stream that an application acquires through the ReadFile function.

The value should be set to 255 in my application.

Quote:

The IOCTL_SERIAL_XOFF_COUNTER request sets an XOFF counter. An XOFF counter request supports clients that use software to emulate hardware handshake flow control.

This value needs to be written after writing 5 bytes of data onto the RS232 port, the value for which is the byte array which I have posted in the original question. hope this helps!

NevemTeve · 07-24-2015, 04:00 AM

That's nice, but you have to find out if they actually do something useful, and if they do then exactly what it is, and how can that be emulated in unix.

sundialsvcs · 07-28-2015, 09:55 PM

It may well be that they cannot.

ioctl() is sort-of the "wild card" in the device-interface world: it lets you pass "a request-code and associated parameters" to the driver, but it really doesn't say what those mean. "That's strictly between you and the driver." (And furthermore, "the driver" might be provided by the vendor of the device in question.)

The operating systems in question basically "just implement the ability to get the job done." Beyond that, it's up to the driver.