Custom ioctl on Linux FORE200E ATM driver

[dalves]

I need to pass a user-space pointer for a 64 bit memory chunk to the FORE200E Linux ATM driver so that the driver can write in it. I was thinking of using the ioctl() call to perform this custom "operation" of the recording the user-space pointer in the driver module.

I open the socket without a problem:

atmSocket = socket(PF_ATMPVC, SOCK_DGRAM, 0);

I can do setsockopt(atmSocket, ...), send(atmSocket, ...) and recv(atmSocket, ...) calls also without a problem.

However, regardless of the cmd I pass to the ioctl() call, it always fails with the "No such device" error message:

int someInt;
ioctl(atmSocket, FIOGETOWN, &someInt);
perror("ioctl");

-> ioctl: No such device

What am I doing wrong?

[Rubberman]

You need to test the return value from the ioctl() call. If it returns a zero, then it succeeded, otherwise it should return a -1 if there is an error. You are also not clearing errno before your ioctl() call, which is a mistake - the output of perror() may be because it hasn't been reset before the ioctl() call.

One final observation, is that your integer someInt is a 32-bit value, not 64-bits, yet you said that you need a 64-bit chunk to pass with the ioctl(). So, declare it as a long long int. That will force it to be 64-bits in size.