linux-kernel - Re: [PATCH 2/4] m68k: Replace NR_syscalls macro from asm/unistd.h

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Message-ID: <CAMuHMdUcg-73DNNGuG3Kn9oQ9R+LpYxpWYV_1tmzN-EzBFUXVQ@mail.gmail.com>
Date:   Tue, 18 Sep 2018 12:04:31 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     firoz.khan@...aro.org
Cc:     linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        y2038 Mailman List <y2038@...ts.linaro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Arch <linux-arch@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        marcin.juszkiewicz@...aro.org
Subject: Re: [PATCH 2/4] m68k: Replace NR_syscalls macro from asm/unistd.h

Hi Firoz,

On Tue, Sep 18, 2018 at 9:16 AM Firoz Khan <firoz.khan@...aro.org> wrote:
> On 9 August 2018 at 13:00, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > One first comment below...
> >
> > On Thu, Aug 9, 2018 at 7:16 AM Firoz Khan <firoz.khan@...aro.org> wrote:
> >> NR_syscalls macro holds the number of system call exist in m68k
> >> architecture. This macro is currently the part of asm/unistd.h file.
> >> We have to change the value of NR_syscalls, if we add or delete a
> >> system call.
> >>
> >> One of patch in this patch series has a script which will generate
> >> a uapi header based on syscall.tbl file. The syscall.tbl file
> >> contains the number of system call information. So we have two
> >> option to update NR_syscalls value.
> >>
> >> 1. Update NR_syscalls in asm/unistd.h manually by counting the
> >>    no.of system calls. No need to update NR_syscalls untill
> >>    we either add a new system call or delete an existing system
> >>    call.
> >>
> >> 2. We can keep this feature it above mentioned script, that'll
> >>    count the number of syscalls and keep it in a generated file.
> >>    In this case we don't need to explicitly update NR_syscalls
> >>    in asm/unistd.h file.
> >>
> >> The 2nd option will be the recommended one. For that, I moved the
> >> NR_syscalls macro from asm/unistd.h to uapi/asm/unistd.h. The macro
> >> name also changed form NR_syscalls to __NR_syscalls for making the
> >> name convention same across all architecture. While __NR_syscalls
> >> isn't strictly part of the uapi, having it as part of the generated
> >> header to simplifies the implementation.
> >
> > It can indeed not be part of the UAPI, as UAPI definitions can never change,
> > while new syscalls will be added in the future, increasing the number ;-)
>
> Thanks for your reply :)
> Sorry for the delayed response :(
>
> I would like to keep __NR_syscalls macro to uapi header in order to simplify
> the system call table generation script. Otherwise the __NR_syscalls
> macro need to update manually. That become a problem.
>
> Please check the below implementation in uapi file make sense?
> It is an easy workaround to leave __NR_syscalls macro in uapi/asm/unistd.h
> and enclose it in #ifdef __KERNEL__
>
> ...
> ...
> #define __NR_pwritev2  378
> #define __NR_statx      379
>
> #ifdef __KERNEL__
> #define __NR_syscalls   380
> #endif
> ...
> ...

#ifdef __KERNEL__ sounds fine to me.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds