linux-kernel - RE: [PATCH] media: staging: rkisp1: rsz: make const array static, makes object smaller

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Message-ID: <d5663dec063440129bf6c373aa252d51@AcuMS.aculab.com>
Date:   Tue, 20 Oct 2020 15:29:46 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Colin King' <colin.king@...onical.com>,
        Helen Koike <helen.koike@...labora.com>,
        Dafna Hirschfeld <dafna.hirschfeld@...labora.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>
CC:     "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] media: staging: rkisp1: rsz: make const array static,
 makes object smaller

From: Colin King
> Sent: 20 October 2020 15:47
> 
> From: Colin Ian King <colin.king@...onical.com>
> 
> Don't populate the const array dev_names on the stack but instead it
> static. Makes the object code smaller by 15 bytes.
> 
> Before:
>    text	   data	    bss	    dec	    hex	filename
>   17091	   2648	     64	  19803	   4d5b	media/rkisp1/rkisp1-resizer.o
> 
> After:
>    text	   data	    bss	    dec	    hex	filename
>   17012	   2712	     64	  19788	   4d4c	media/rkisp1/rkisp1-resizer.o
> 
> (gcc version 10.2.0)
> 
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/staging/media/rkisp1/rkisp1-resizer.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/media/rkisp1/rkisp1-resizer.c b/drivers/staging/media/rkisp1/rkisp1-
> resizer.c
> index 1687d82e6c68..7ca5b47c5bf5 100644
> --- a/drivers/staging/media/rkisp1/rkisp1-resizer.c
> +++ b/drivers/staging/media/rkisp1/rkisp1-resizer.c
> @@ -763,8 +763,10 @@ static void rkisp1_rsz_unregister(struct rkisp1_resizer *rsz)
> 
>  static int rkisp1_rsz_register(struct rkisp1_resizer *rsz)
>  {
> -	const char * const dev_names[] = {RKISP1_RSZ_MP_DEV_NAME,
> -					  RKISP1_RSZ_SP_DEV_NAME};
> +	static const char * const dev_names[] = {
> +		RKISP1_RSZ_MP_DEV_NAME,
> +		RKISP1_RSZ_SP_DEV_NAME
> +	};
>  	struct media_pad *pads = rsz->pads;
>  	struct v4l2_subdev *sd = &rsz->sd;
>  	int ret;

Don't look at what that code is actually doing....
It is rather horrid.
rkisp1_rsz_register() is called for each entry in an array (twice).
The array index is written into rsz->id.
The value is then used to select one of the two strings.
But rsz->id is actually an enum type.

rkisp1_rsz_register() should probably just be called twice with some
extra parameters.

	David

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