Date:   Fri, 3 Mar 2023 17:13:06 +0800
From:   Baoquan He <bhe@redhat.com>
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     linux-kernel@vger.kernel.org,
        Linux-Arch <linux-arch@vger.kernel.org>, linux-mm@kvack.org,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Christoph Hellwig <hch@infradead.org>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Huacai Chen <chenhuacai@kernel.org>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        linux-mips@vger.kernel.org
Subject: Re: [PATCH v2 1/2] mips: add <asm-generic/io.h> including
Message-ID: <ZAG6Ilwj7+pcJdK7@MiWiFi-R3L-srv>
References: <20230301102208.148490-1-bhe@redhat.com>
 <20230301102208.148490-2-bhe@redhat.com>
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On 03/02/23 at 08:12am, Arnd Bergmann wrote:
> On Thu, Mar 2, 2023, at 05:12, Baoquan He wrote:
> > On 03/01/23 at 03:06pm, Arnd Bergmann wrote:
> >
> > Yeah, defining mmiowb() to wmb() directly is also good to me. I tried
> > to comb including sequence and find where asm/io.h is included, but
> > failed. Mainly asm/mmiowb.h including asm/io.h will cause below
> > compiling error, the asm/io.h need see mmiowb_set_pending which is
> > defnined in asm-generic/mmiowb.h. Moving asm-generic/mmiowb.h to above
> > asm/io.h can also fix the compiling error.
> >
> > =============
> > diff --git a/arch/mips/include/asm/mmiowb.h b/arch/mips/include/asm/mmiowb.h
> > index a40824e3ef8e..cae2745935bc 100644
> > --- a/arch/mips/include/asm/mmiowb.h
> > +++ b/arch/mips/include/asm/mmiowb.h
> > @@ -2,10 +2,8 @@
> >  #ifndef _ASM_MMIOWB_H
> >  #define _ASM_MMIOWB_H
> > 
> > +#include <asm-generic/mmiowb.h>
> >  #include <asm/io.h>
> > 
> >  #define mmiowb()       iobarrier_w()
> > -
> > -#include <asm-generic/mmiowb.h>
> > -
> >  #endif /* _ASM_MMIOWB_H */
> 
> According to the comment in asm-generic/mmiowb.h, the intention is
> to have the mmiowb definition before the #include, though this would
> only be necessary if there was an "#ifndef mmiowb" fallback in that
> file. If the definition to wmb() works, I'd go for that one and
> leave the include order unchanged.

I didn't add definition of outb(), so it caused the compiling error at
below. Adding it can fix that. I will leave the asm/mmiowb.h as is
since no issue now.

In file included from ./arch/mips/include/asm/io.h:611,
                 from ./arch/mips/include/asm/mmiowb.h:5,
                 from ./include/linux/spinlock.h:65,
                 from ./include/linux/ipc.h:5,
                 from ./include/uapi/linux/sem.h:5,
                 from ./include/linux/sem.h:5,
                 from ./include/linux/compat.h:14,
                 from arch/mips/kernel/asm-offsets.c:12:
./include/asm-generic/io.h: In function ‘_outb’:
./include/asm-generic/io.h:46:24: error: implicit declaration of function ‘mmiowb_set_pending’ [-Werror=implicit-function-declaration]
   46 | #define __io_aw()      mmiowb_set_pending()
      |                        ^~~~~~~~~~~~~~~~~~
./include/asm-generic/io.h:54:24: note: in expansion of macro ‘__io_aw’
   54 | #define __io_paw()     __io_aw()
      |                        ^~~~~~~
./include/asm-generic/io.h:585:9: note: in expansion of macro ‘__io_paw’
  585 |         __io_paw();
      |         ^~~~~~~~