Re: checkpatch.pl: Use of extern in function prototype

[Joe Perches <joe@perches.com>]

On Mon, 2014-08-18 at 15:09 +0530, Arun Chandran wrote:
> Hi,
> 
> I have a piece of code as shown below.
> 
> #######################
> diff --git a/arch/arm64/include/asm/proc-fns.h
> b/arch/arm64/include/asm/proc-fns.h
> index 9a8fd84..86be4f9 100644
> --- a/arch/arm64/include/asm/proc-fns.h
> +++ b/arch/arm64/include/asm/proc-fns.h
> @@ -32,7 +32,7 @@ extern void cpu_cache_off(void);
>  extern void cpu_do_idle(void);
>  extern void cpu_do_switch_mm(unsigned long pgd_phys, struct mm_struct *mm);
>  extern void cpu_reset(unsigned long addr) __attribute__((noreturn));
> +extern void cpu_soft_restart(phys_addr_t cpu_reset,
>                 unsigned long addr) __attribute__((noreturn));
>  extern void cpu_do_suspend(struct cpu_suspend_ctx *ptr);
>  extern u64 cpu_do_resume(phys_addr_t ptr, u64 idmap_ttbr);
> ########################
> 
> Other lines had an "extern" in them I also added it blindly.
> when the above code is given checkpatch.pl did not throw any
> error/warning,; but I got this reply
> 
> http://lists.infradead.org/pipermail/linux-arm-kernel/2014-August/279691.html
> 
> [[As the functions have external linkage by default, the extern keyword is
> irrelevant in this case.]]
> 
> Does checkpatch.pl misbehave in my case?

checkpatch's "unnecessary extern" message is somewhat controversial.

It requires the use of "--strict" on the command line.