Raspberry Pi 5 uses external RP1 Chip (via PCIe) https://datasheets.raspberrypi.com/rp1/rp1-peripherals.pdf
The Registers are complete different from Pi 4 (64 GPIOs with GPFSEL0-GPFSEL5, 3 bit Function definition compared to Pi 5 with 28 GPIOs with STATUS and CTRL Register per GPIO)
Need a complete new implementation and understanding of register access.

Raspberry Pi 5 GPIO uses /dev/gpiomem0 - absolute address unknown/untested.