What should be the value of ngpio field for multiplexed GPIO Pins

[rishi gupta <gupt21@xxxxxxxxx>]

Hello,
I am writing driver for USB Based device which has 4 pins which can be
configured for GPIO or alternate functions. 2 pins are configured for
GPIO while other 2 pins for alternate function. In this scenario, what
is correct approach 1 or 2 and why from linux gpio framework
perspective?

1. Register all 4 pins and return -ENODEV in request calback for pins
used for alternate function.
struct gpio_chip *gc;
gc.ngpio = 4;

2. Register only 2: gc.ngpio = 2;

Regards,
Rishi