Default Qualcomm Diag Mode without USB connection to PC

Hello guys,

I am curious, what the /dev/diag device can be used for. Does anyone know its purpose? Regarding the Kconfig of /drivers/char/diag, this virtual device is an interface for exchanging diag data. However, performing a cat on that device file, resulted in an error:
cat: /dev/diag: Bad address
Echo-ing the 4-byte-version-query into the diag-device did not result in an error. But nothing else happened, either.

I would like to be able to access the baseband's diag data without having a computer attached to the phone's USB port - and, if even possible, without even modifying the kernel.

My new Game FruitPunch. XDA-Thread
and my Live Wallpapers (XDA)