Re: [PATCH 2/4] mm: ioremap: Add arch_ioremap/iounmap_check()

[Kefeng Wang]

On 2022/4/28 2:20, Arnd Bergmann wrote:
> On Wed, Apr 27, 2022 at 2:14 PM Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
> > @@ -964,6 +964,9 @@ static inline void iounmap(volatile void __iomem *addr)
> >   #elif defined(CONFIG_GENERIC_IOREMAP)
> >   #include <linux/pgtable.h>
> >
> > +bool arch_ioremap_check(phys_addr_t addr, size_t size, unsigned long prot);
> > +bool arch_iounmap_check(void __iomem *addr);
> > +
> >   void __iomem *ioremap_prot(phys_addr_t addr, size_t size, unsigned long prot);
> >   void iounmap(volatile void __iomem *addr);
> >
> > diff --git a/mm/ioremap.c b/mm/ioremap.c
> > index 522ef899c35f..d1117005dcc7 100644
> > --- a/mm/ioremap.c
> > +++ b/mm/ioremap.c
> > @@ -11,6 +11,16 @@
> >   #include <linux/io.h>
> >   #include <linux/export.h>
> >
> > +bool __weak arch_ioremap_check(phys_addr_t addr, size_t size, unsigned long prot)
> > +{
> > +       return true;
> > +}
> > +
> > +bool __weak arch_iounmap_check(void __iomem *addr)
> > +{
> > +       return true;
> > +}
> > +
> I don't really like the weak functions. The normal way to do this in
> asm-generic headers
> is to have something like
>
> #ifndef arch_ioremap_check
> static inline bool arch_ioremap_check(phys_addr_t addr, size_t size,
> unsigned long prot)
> {
>         return true;
> }
> #endif
>
> and then in architectures that actually do some checking, have these
> bits in asm/io.h
>
> bool arch_ioremap_check(phys_addr_t addr, size_t size, unsigned long prot);
> #define arch_ioremap_check arch_ioremap_check
Ok, I could use this way, and keep consistent with others definitions in 
asm/io.h
> (or alternatively an extern declaration, if the implementation is nontrivial)
>
> It may be worth pointing out that either way requires including
> asm-generic/io.h,
> which most architectures don't. This is probably fine, as only csky, riscv and
> now arm64 use CONFIG_GENERIC_IOREMAP, and we can probably require
> that any further architectures using this symbol also have to use
> asm-generic/io.h.

It looks the arch is already include it,

$ git grep "asm-generic/io.h" arch/

arch/arc/include/asm/io.h:#include <asm-generic/io.h>
arch/arm/include/asm/io.h:#include <asm-generic/io.h>
arch/arm64/include/asm/io.h:#include <asm-generic/io.h>
arch/csky/include/asm/io.h:#include <asm-generic/io.h>
arch/h8300/include/asm/io.h:#include <asm-generic/io.h>
arch/ia64/include/asm/io.h:#include <asm-generic/io.h>
arch/m68k/include/asm/io.h:#include <asm-generic/io.h>
arch/m68k/include/asm/io_no.h: * that behavior here first before we 
include asm-generic/io.h.
arch/microblaze/include/asm/io.h:#include <asm-generic/io.h>
arch/nios2/include/asm/io.h:#include <asm-generic/io.h>
arch/openrisc/include/asm/io.h:#include <asm-generic/io.h>
arch/powerpc/include/asm/io.h:#include <asm-generic/io.h>
arch/riscv/include/asm/io.h:#include <asm-generic/io.h>
arch/s390/include/asm/io.h:#include <asm-generic/io.h>
arch/sparc/include/asm/io_32.h:#include <asm-generic/io.h>
arch/um/include/asm/io.h:#include <asm-generic/io.h>
arch/x86/include/asm/io.h:#include <asm-generic/io.h>
arch/xtensa/include/asm/io.h:#include <asm-generic/io.h>

>        Arnd
>
> .