linux-kernel - Re: [PATCH] drm/bridge/tc358767: make the array ext

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Date:   Thu, 19 Aug 2021 06:51:23 -0700
From:   Joe Perches <joe@...ches.com>
To:     Colin King <colin.king@...onical.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/bridge/tc358767: make the array ext_div static
 const, makes object smaller

On Thu, 2021-08-19 at 14:38 +0100, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> Don't populate the array ext_div on the stack but instead it
> static const. Makes the object code smaller by 118 bytes:
> 
> Before:
>    text    data    bss     dec    hex filename
>   39449   17500    128   57077   def5 ./drivers/gpu/drm/bridge/tc358767.o
> 
> After:
>    text    data    bss     dec    hex filename
>   39235   17596    128   56959   de7f ./drivers/gpu/drm/bridge/tc358767.o

Why is text smaller and data larger with this change?

> 
> (gcc version 10.3.0)
> 
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/gpu/drm/bridge/tc358767.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
> index 23a6f90b694b..599c23759400 100644
> --- a/drivers/gpu/drm/bridge/tc358767.c
> +++ b/drivers/gpu/drm/bridge/tc358767.c
> @@ -468,7 +468,7 @@ static int tc_pxl_pll_en(struct tc_data *tc, u32 refclk, u32 pixelclock)
>  	int div, best_div = 1;
>  	int mul, best_mul = 1;
>  	int delta, best_delta;
> -	int ext_div[] = {1, 2, 3, 5, 7};
> +	static const int ext_div[] = {1, 2, 3, 5, 7};
>  	int best_pixelclock = 0;
>  	int vco_hi = 0;
>  	u32 pxl_pllparam;