Ok let’s try it again:
A USB Stick has serveral Descriptors, that are located on the ROM of the Stick.
With the Device- and Stringdescriptor I am able to indetify a unique USB Device.
A Linux System can have serveral USB Hostcontroller and each Hostcontroller can have up to 127 USB Devices.
The Device Number is asigned depending on the number of usb devices already connected to the Hostcontroller.
I am writing a cpp programm, where i need to access the descriptors an the files of the same USB Stick.
The usbd_() functions allow me to get the descriptors of a USB Device.
To adress a USB Device in the usbd_() functions you cannot use the name of a device (that is has in /dev/) but the USB Hostcontroller Number and Device Number.
After iterating over all the USB Hostcontroller and their USB Devices i finally identified the unique USB Stick with its descriptors (in case it is plugged in).
Now i need to to know, where i can access this USB Device (on Hostcontroller X with Device Number Y) in the filesystem.
How do I connect the Host-/DeviceNumber of a USB Device to its entry in /dev/?
If I knew, i could conclude to its mounting point in /fs/.