How to know the USB port number?

I am using a USB hub with 7 downstream ports.
I am connecting 4 of the same devices(custom class device) on 4 ports.
I have a requirement to know to which physical port is a device connected, cause I have to number them accordingly in the application GUI.

I found an ioctl USBDEVFS_HUB_PORTINFO, in "usbdevice_fs.h" which does give me this information.
"hub_ioctl" does give us this information.

now I don't know how to call this ioctl from my application.

Do I have to make any provision in my device driver to talk to the hub driver? if so can anyone please explain me how do we do that.
I did google on this but it seems to be very trivial, so could not find any information.

Note: am using 2.6.22 on i.Mx21S target
Thanks in advance
Basavesh