I have an problem with linux not being able to register a gpiochip on a custom FPGA board (Cyclone V).
I get the following error during kernel boot
_piochip_add: gpios -1…30 (/sopc@0/bridge@0xff200000/gpio@0x1000107a0) failed to register
/sopc@0/bridge@0xff200000/gpio@0x1000107a0: GPIO chip registration failed with status -28
altera_gpio ff2107a0.gpio: Failed adding memory mapped gpiochip
altera_gpio: probe of ff2107a0.gpio failed with error -28
After the kernel has complete the boot the folder ‘’/sys/class/fpga-bridge’’ is completely empty.
Does anyone know what error code -28 mean?