Re: [PATCH v2] sparc: Avoid -Wunused-but-set-parameter in clear_user_page()

On 2026-05-25 10:44:39-0700, Andrew Morton wrote:
> On Mon, 25 May 2026 10:36:21 +0200 Thomas Weißschuh <[email protected]> wrote:
> 
> > The loop in clear_user_pages() iterates over all pages and calls
> > clear_user_page() for each of them. During the loop "vaddr" is modified.
> > However on sparc clear_user() is a macro which does not use "vaddr".
> > The compiler sees a variable which is modified but never used and emits
> > a warning for that:
> > 
> > 	include/linux/highmem.h: In function 'clear_user_pages':
> > 	include/linux/highmem.h:234:63: warning: parameter 'vaddr' set but not used [-Wunused-but-set-parameter=]
> > 		static inline void clear_user_pages(void *addr, unsigned long vaddr,
> > 
> > Other architectures use an inline function for clear_user_page() which
> > avoids the warning. This is not possible on sparc, as
> > sparc_flush_page_to_ram() is not yet declared where clear_user_page() is
> > defined. Including cacheflush_32.h will trigger recursive and lots of
> > other issues.
> > 
> > So hide the warning with a cast to (void) instead.
> > 
> > While we are here, do the same for copy_user_page().
> 
> A pleasing solution to these sorts of problems is often "don't use
> macros".  Other architectures use inlined C for these functions - will
> that work for sparc?

Probably yes. But it would require a major reshuffling of the header
files to get the dependencies right. So I went with the easy solution to
avoid a lot of churn. As I tried to explain this in the patch message.


Thomas