Re: [PATCH] [media] vivid: don't use more than 1024 bytes of stack

[Hans Verkuil <hverkuil@xs4all.nl>]

On 06/05/2015 12:29 PM, Mauro Carvalho Chehab wrote:
> Remove the following compilation warnings:
> 
> 	drivers/media/platform/vivid/vivid-tpg.c: In function 'tpg_gen_text':
> 	drivers/media/platform/vivid/vivid-tpg.c:1562:1: warning: the frame size of 1308 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> 	 }
> 	 ^
> 
> This seems to be due to some bad optimization done by gcc.
> 
> Moving the for() loop to happen inside the macro solves the
> issue.

Huh, interesting. I'd never have guessed that.

Acked-by: Hans Verkuil <hans.verkuil@cisco.com>

Thanks for looking at this!

	Hans

> 
> While here, fix CodingStyle at the switch().
> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
> 
> diff --git a/drivers/media/platform/vivid/vivid-tpg.c b/drivers/media/platform/vivid/vivid-tpg.c
> index b1147f2df26c..7a3ed580626a 100644
> --- a/drivers/media/platform/vivid/vivid-tpg.c
> +++ b/drivers/media/platform/vivid/vivid-tpg.c
> @@ -1492,12 +1492,10 @@ void tpg_gen_text(const struct tpg_data *tpg, u8 *basep[TPG_MAX_PLANES][2],
>  	else if (tpg->field == V4L2_FIELD_SEQ_TB || tpg->field == V4L2_FIELD_SEQ_BT)
>  		div = 2;
>  
> -	for (p = 0; p < tpg->planes; p++) {
> -		unsigned vdiv = tpg->vdownsampling[p];
> -		unsigned hdiv = tpg->hdownsampling[p];
> -
> -		/* Print text */
> -#define PRINTSTR(PIXTYPE) do {	\
> +	/* Print text */
> +#define PRINTSTR(PIXTYPE) for (p = 0; p < tpg->planes; p++) {	\
> +	unsigned vdiv = tpg->vdownsampling[p];	\
> +	unsigned hdiv = tpg->hdownsampling[p];	\
>  	PIXTYPE fg;	\
>  	PIXTYPE bg;	\
>  	memcpy(&fg, tpg->textfg[p], sizeof(PIXTYPE));	\
> @@ -1548,16 +1546,19 @@ void tpg_gen_text(const struct tpg_data *tpg, u8 *basep[TPG_MAX_PLANES][2],
>  	}	\
>  } while (0)
>  
> -		switch (tpg->twopixelsize[p]) {
> -		case 2:
> -			PRINTSTR(u8); break;
> -		case 4:
> -			PRINTSTR(u16); break;
> -		case 6:
> -			PRINTSTR(x24); break;
> -		case 8:
> -			PRINTSTR(u32); break;
> -		}
> +	switch (tpg->twopixelsize[p]) {
> +	case 2:
> +		PRINTSTR(u8);
> +		break;
> +	case 4:
> +		PRINTSTR(u16);
> +		break;
> +	case 6:
> +		PRINTSTR(x24);
> +		break;
> +	case 8:
> +		PRINTSTR(u32);
> +		break;
>  	}
>  }
>  
>