netdev - Re: [PATCH 2/2] net: ipv4: Use BIT macro.

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Message-ID: <1490818609.24891.49.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Wed, 29 Mar 2017 13:16:49 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Varsha Rao <rvarsha016@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>,
        outreachy-kernel <outreachy-kernel@...glegroups.com>,
        netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] net: ipv4: Use BIT macro.

On Thu, 2017-03-30 at 00:46 +0530, Varsha Rao wrote:
> Replace bitwise left shift by one operations with BIT() macro. This patch
> fixes the checkpatch issue.
> 
> Signed-off-by: Varsha Rao <rvarsha016@...il.com>
> ---
>  net/ipv4/tcp_bbr.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c
> index 4da4bc1..9f2c869 100644
> --- a/net/ipv4/tcp_bbr.c
> +++ b/net/ipv4/tcp_bbr.c
> @@ -71,10 +71,10 @@
>   * an issue. The upper bound isn't an issue with existing technologies.
>   */
>  #define BW_SCALE 24
> -#define BW_UNIT (1 << BW_SCALE)
> +#define BW_UNIT BIT(BW_SCALE)
>  
>  #define BBR_SCALE 8	/* scaling factor for fractions in BBR (e.g. gains) */
> -#define BBR_UNIT (1 << BBR_SCALE)
> +#define BBR_UNIT BIT(BBR_SCALE)
>  
>  /* BBR has the following modes for deciding how fast to send: */
>  enum bbr_mode {

Well, no.  BIT() is using unsigned long.

#define BIT(nr)    (1UL << (nr))


This change might have unintended effects.

Maybe checkpatch should be fixed.