linux-kernel - Re: [PATCH] gpio: gpio-stmpe: make various char arrays static const, shrinks object size

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Date:   Wed, 29 Nov 2017 09:19:35 +0100
From:   walter harms <wharms@....de>
To:     Colin King <colin.king@...onical.com>
CC:     Linus Walleij <linus.walleij@...aro.org>,
        linux-gpio@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpio: gpio-stmpe: make various char arrays static const,
 shrinks object size



Am 28.11.2017 19:23, schrieb Colin King:
> From: Colin Ian King <colin.king@...onical.com>
> 
> Don't populate the read-only arrays edge_det_values, rise_values and
> fall_values on the stack but instead make them static and constify them.
> Makes the object code smaller by over 240 bytes:
> 
> Before:
>    text	   data	    bss	    dec	    hex	filename
>    9525	   2520	    192	  12237	   2fcd	drivers/gpio/gpio-stmpe.o
> 
> After:
>    text	   data	    bss	    dec	    hex	filename
>    9025	   2776	    192	  11993	   2ed9	drivers/gpio/gpio-stmpe.o
> 
> (gcc version 7.2.0 x86_64)
> 
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/gpio/gpio-stmpe.c | 24 +++++++++++++++---------
>  1 file changed, 15 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpio/gpio-stmpe.c b/drivers/gpio/gpio-stmpe.c
> index e6e5cca624a7..e3d048e65339 100644
> --- a/drivers/gpio/gpio-stmpe.c
> +++ b/drivers/gpio/gpio-stmpe.c
> @@ -273,15 +273,21 @@ static void stmpe_dbg_show_one(struct seq_file *s,
>  		u8 fall_reg;
>  		u8 irqen_reg;
>  
> -		char *edge_det_values[] = {"edge-inactive",
> -					   "edge-asserted",
> -					   "not-supported"};
> -		char *rise_values[] = {"no-rising-edge-detection",
> -				       "rising-edge-detection",
> -				       "not-supported"};
> -		char *fall_values[] = {"no-falling-edge-detection",
> -				       "falling-edge-detection",
> -				       "not-supported"};
> +		static const char * const edge_det_values[] = {
> +			"edge-inactive",
> +			"edge-asserted",
> +			"not-supported"
> +		};
> +		static const char * const rise_values[] = {
> +			"no-rising-edge-detection",
> +			"rising-edge-detection",
> +			"not-supported"
> +		};
> +		static const char * const fall_values[] = {
> +			"no-falling-edge-detection",
> +			"falling-edge-detection",
> +			"not-supported"
> +		};
>  		#define NOT_SUPPORTED_IDX 2

@maintainer:
the define here is hard to find, perhaps i should be move to a place
where i can be found more easily. Like the beginning of line.

re,
 wh
>  		u8 edge_det = NOT_SUPPORTED_IDX;
>  		u8 rise = NOT_SUPPORTED_IDX;