On Monday 25 January 2010, Anton Vorontsov wrote:

With this patch there are two ways to register OF GPIO controllers:

1. Allocating the of_gpio_chip structure and passing the
   &of_gc->gc pointer to the gpiochip_add. (Can use container_of
   to convert the gpio_chip to the of_gpio_chip.)

2. Allocating and registering the gpio_chip structure separately
   from the of_gpio_chip. (Since two allocations are separate,
   container_of won't work.)

As time goes by we'll kill the first option.

Why have two options, instead of just the first/simpler one??