Mity CPU Platforms » MitySOM-5CSX Altera Cyclone V

Hi,
I have added pio ip (output only) to the HPS block design in platform designer, and modified/added gpio block with address specification by converting the dtb file to dts. Again compiled back to new dtb and replaced in pre built os image contained emmc card. After booting I am able to gpio chip in and as /sys/class/gpio/gpiochip1984. I have made pio out signal as external and added to signal tap analyser in top module to view the value. Whaen I try to run echo commands, it is permission denied. How can I access the gpio to send 32 bit data from HPS to FPGA. And my actual requirement is to send 256 bit(32X8) data, is it allowed add any number of pio modules.
Thank you.