On Wed, Feb 24, 2021 at 2:57 AM Masahiro Yamada [off-list ref] wrote:

On Wed, Feb 24, 2021 at 5:04 AM Arnd Bergmann [off-list ref] wrote:

quoted

On Tue, Feb 23, 2021 at 11:06 AM Masahiro Yamada [off-list ref] wrote:

My intention is to improve the UAPI/KAPI decoupling
to decrease the task of scripts/headers_install.sh

Ideally, we could export UAPI headers with
almost no modification.

It is true that scripts/unifdef can remove #ifndef __KERNEL__
blocks, but having the kernel-space code in UAPI headers
does not make sense. Otherwise, our initial motivation
"separate them by directory structure" would be lost.

So, I believe redefining _IOC_TYPECHECK is the right direction.
I can add comments if this is not clear.

Maybe using '#ifndef _IOC_TYPECHECK' would help here?

Another alternative might be to find a way to rewrite the typecheck
macro to make it safe to be used in user space as well, and not
have two different versions.

       Arnd