linux-kernel - Re: [PATCH] powerpc: use ARRAY_SIZE instead of division operation

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Date:   Mon, 22 Feb 2021 12:40:26 +1100
From:   Daniel Axtens <dja@...ens.net>
To:     Yang Li <yang.lee@...ux.alibaba.com>, mpe@...erman.id.au
Cc:     benh@...nel.crashing.org, paulus@...ba.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Yang Li <yang.lee@...ux.alibaba.com>
Subject: Re: [PATCH] powerpc: use ARRAY_SIZE instead of division operation

Hi Yang,

> This eliminates the following coccicheck warning:
> ./arch/powerpc/boot/mktree.c:130:31-32: WARNING: Use ARRAY_SIZE
>
> Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
> Signed-off-by: Yang Li <yang.lee@...ux.alibaba.com>
> ---
>  arch/powerpc/boot/mktree.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/boot/mktree.c b/arch/powerpc/boot/mktree.c
> index dc603f3..0b2def5 100644
> --- a/arch/powerpc/boot/mktree.c
> +++ b/arch/powerpc/boot/mktree.c
> @@ -127,7 +127,7 @@ int main(int argc, char *argv[])
>  			exit(5);
>  		}
>  		cp = tmpbuf;
> -		for (i = 0; i < sizeof(tmpbuf) / sizeof(unsigned int); i++)
> +		for (i = 0; i < ARRAY_SIZE(tmpbuf); i++)

Unfortunately this breaks the build - see
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/1613808853-78381-1-git-send-email-yang.lee@linux.alibaba.com/

This is because 'boot/mktree.c' is a userspace program without access to
the usual kernel headers.

It might be best to get coccicheck to exclude all of
'arch/powerpc/boot/' as I believe everything in that directory is
compiled differently to the rest of the kernel (see the Makefile), but
maybe just blacklisting boot/mktree.c would be sufficient.

Kind regards,
Daniel

>  			cksum += *cp++;
>  		if (write(out_fd, tmpbuf, sizeof(tmpbuf)) != sizeof(tmpbuf)) {
>  			perror("boot-image write");
> -- 
> 1.8.3.1