Re: [PATCH v3 08/26] compat_ioctl: add compat_ptr_ioctl()

[Al Viro]

On Tue, Apr 16, 2019 at 10:19:46PM +0200, Arnd Bergmann wrote:
> Many drivers have ioctl() handlers that are completely compatible between
> 32-bit and 64-bit architectures, except for the argument that is passed
> down from user space and may have to be passed through compat_ptr()
> in order to become a valid 64-bit pointer.
> 
> Using ".compat_ptr = compat_ptr_ioctl" in file operations should let
> us simplify a lot of those drivers to avoid #ifdef checks, and convert
> additional drivers that don't have proper compat handling yet.

You forgot to mention that it even gets the previous commit to build ;-)
IOW, that needs to be reordered.