Re: [PATCH] ARM: efi: Simplify arch_efi_call_virt() macro by using typeof()

[Sudeep Holla <sudeep.holla@arm.com>]

On Tue, Jun 28, 2022 at 03:16:26PM +0200, Ard Biesheuvel wrote:
> On Tue, 28 Jun 2022 at 14:59, Sudeep Holla <sudeep.holla@arm.com> wrote:
> >
> > Currently, the arch_efi_call_virt() assumes all users of it will have
> > defined a type 'efi_##f##_t' to make use of it. It is unnecessarily
> > forcing the users to create a new typedef when __efi_rt_asm_wrapper()
> > actually expects void pointer.
> >
> > Simplify the arch_efi_call_virt() macro by using typeof(p->f) which must
> > be a pointer as required by __efi_rt_asm_wrapper() and eliminate the
> > explicit need for efi_##f##_t type for every user of this macro.
> >
> > This change is done to align with implementations on other similar
> > architectures.
> >
> > Cc: Ard Biesheuvel <ardb@kernel.org>
> > Cc: Russell King <linux@armlinux.org.uk>
> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> > ---
> >  arch/arm/include/asm/efi.h | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > Hi,
> >
> > Reference for this change [1] and in particular[2]
> >
> > Regards,
> > Sudeep
> >
> > [1] https://lore.kernel.org/r/20220628125346.693304-1-sudeep.holla@arm.com
> > [2] https://lore.kernel.org/r/20220628125346.693304-3-sudeep.holla@arm.com/
> >
> > diff --git a/arch/arm/include/asm/efi.h b/arch/arm/include/asm/efi.h
> > index 27218eabbf9a..d4a405c9b4b6 100644
> > --- a/arch/arm/include/asm/efi.h
> > +++ b/arch/arm/include/asm/efi.h
> > @@ -26,8 +26,7 @@ int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);
> >
> >  #define arch_efi_call_virt(p, f, args...)                              \
> >  ({                                                                     \
> > -       efi_##f##_t *__f;                                               \
> > -       __f = p->f;                                                     \
> > +       typeof(p->f) __f = p->f;                                        \
> >         __f(args);                                                      \
> >  })
> >
> 
> I think this could simply be
> 
> #define arch_efi_call_virt(p, f, args...) ((p)->f(args))
> 
> no?

Yes, I came to similar conclusion just after sending this out as I started to
look if we can have one generic definition for arm/arm64/riscv/loongarch.

I am yet to figure out how asm/efi.h and linux/efi.h are included so that
we can have generic definition in linux/efi.h and x86 can undefine that
and redefine its own version.

Does that make sense ?

--
Regards,
Sudeep

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