On Mon, Feb 12, 2018 at 01:45:31PM +0100, Linus Walleij wrote:

> The non-generic bitbang was a feature where a platform could optimize
> SPI bit-banging by inlining the routines to hammer GPIO lines into
> the GPIO bitbanging driver as direct register writes using a custom
> set of GPIO library calls.

> It does not work with multiplatform concepts, violates everything
> about how GPIO is made generic and is just generally a bad idea,
> even on legacy system. Also there is no single user in the entire
> kernel (for good reasons).

It's not expected that users should go upstream and it doesn't seem
helpful to delete without replacement.  The original idea was to allow
things like setting multiple GPIOs at once if there were calls for that,
now that gpiolib has support for that we should at least convert to it
before removing the hook.