linux-kernel - Re: [PATCH v8 18/25] powerpc: Implement nvram sync ioctl

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Date:   Mon, 31 Dec 2018 13:17:33 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Finn Thain <fthain@...egraphics.com.au>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH v8 18/25] powerpc: Implement nvram sync ioctl

On Mon, Dec 31, 2018 at 12:13 AM Finn Thain <fthain@...egraphics.com.au> wrote:
> On Sun, 30 Dec 2018, Finn Thain wrote:
> > > > diff --git a/include/linux/nvram.h b/include/linux/nvram.h
> > > > index b7bfaec60a43..24a57675dba1 100644
> > > > --- a/include/linux/nvram.h
> > > > +++ b/include/linux/nvram.h
> > > > @@ -18,8 +18,12 @@ struct nvram_ops {
> > > >         unsigned char   (*read_byte)(int);
> > > >         void            (*write_byte)(unsigned char, int);
> > > >         ssize_t         (*get_size)(void);
> > > > +#ifdef CONFIG_PPC
> > > > +       long            (*sync)(void);
> > > > +#else
> > > >         long            (*set_checksum)(void);
> > > >         long            (*initialize)(void);
> > > > +#endif
> > > >  };
> > >
> > > Maybe just leave all entries visible here, and avoid the above #ifdef
> > > checks.
> > >
> >
> > The #ifdef isn't there just to save a few bytes, though it does do that.
> > It's really meant to cause a build failure when I mess up somewhere. But
> > I'm happy to change it if you can see a reason to do so (?)
> >
>
> I think the problem with these #ifdef conditionals is that they don't
> express the correct constraints. So, at the end of this series I'd prefer
> to see,
>
> struct nvram_ops {
>        ssize_t         (*read)(char *, size_t, loff_t *);
>        ssize_t         (*write)(char *, size_t, loff_t *);
>        unsigned char   (*read_byte)(int);
>        void            (*write_byte)(unsigned char, int);
>        ssize_t         (*get_size)(void);
> #if defined(CONFIG_PPC)
>        long            (*sync)(void);
>        int             (*get_partition)(int);
> #elif defined(CONFIG_X86) || defined(CONFIG_M68K)
>        long            (*set_checksum)(void);
>        long            (*initialize)(void);
> #endif
> };
>
> Is that okay with you?

My preference would be no #ifdef here, but the compile time
error you mention is a good enough reason, so I'm fine with
either version you pick.

       Arnd