Re: [PATCH] asm-generic: replace ________addr with __UNIQUE_ID(addr)

David Laight
2026-04-26T10:49:41Z

On Sat, 25 Apr 2026 15:12:40 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Sat, 25 Apr 2026 23:01:34 +0100 David Laight <david.laight.linux@gmail.com> wrote:
>
> > > > The real problem with this define is that both idx and phys are
> > > > expanded twice.
> > >
> > > The real problem with this define is that it's a define. Why oh why do
> > > we keep doing this to ourselves?
> >
> > Sometimes #defines generate better code because they are expanded earlier,
> > and sometimes you want type-agnostic 'functions'.
> > But neither is true here.
> >
> > But I think I'd go for 'always_inline'.
> > Sometimes the compilers make silly decisions.
>
> Gee, if `static inline' misbehaves then we have big problems!
>
> What's special about the fixmap code anyway? It's not exactly
> fastpath. Perhaps this stuff can simply be uninlined.

Some of the inlines are trivial - just adding an extra parameter.
But this set would be simpler if the last function
(__native_set_fixmap() for x86) returned (address & ~PAGE_MASK)

>
> Pet peeves:
>
> We use too many macros.

Indeed, I get fed up of looking things up to find they are trivial.
Some of the 'helpers' do nothing for core readability.
Even things like BIT() can have unexpected consequences.

Not to say I haven't got the pre-processor to do odd things in the past.
But it is usually trying to avoid having to keep multiple definitions
aligned with each other.

> We inline too much stuff.

True - don't look at what strlcpy() can generate.
The inline code should just get the constants from the compiler and
then call the appropriate function.

As does the compiler.
pixpaper_panel_hw_init() repeatedly calls two static functions that
contain sleeps. They all get inlined bloating the code size and
exploding the stack when clang separately allocates all the buffers
in the called functions.

David