linux-kernel - Re: [Patch 2/2] media: ti-vpe: vpe: allow use of user specified stride

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Date:   Wed, 15 Feb 2017 13:22:42 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...com>
To:     Benoit Parrot <bparrot@...com>, Hans Verkuil <hverkuil@...all.nl>,
        Mauro Carvalho Chehab <mchehab@....samsung.com>,
        <linux-media@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, Jyri Sarha <jsarha@...com>,
        Peter Ujfalusi <peter.ujfalusi@...com>
Subject: Re: [Patch 2/2] media: ti-vpe: vpe: allow use of user specified
 stride

Hi,

On 13/02/17 15:06, Benoit Parrot wrote:
> Bytesperline/stride was always overwritten by VPE to the most
> adequate value based on needed alignment.
> 
> However in order to make use of arbitrary size DMA buffer it
> is better to use the user space provide stride instead.
> 
> The driver will still calculate an appropriate stride but will
> use the provided one when it is larger than the calculated one.
> 
> Signed-off-by: Benoit Parrot <bparrot@...com>
> ---
>  drivers/media/platform/ti-vpe/vpe.c | 28 ++++++++++++++++++++--------
>  1 file changed, 20 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/media/platform/ti-vpe/vpe.c b/drivers/media/platform/ti-vpe/vpe.c
> index 2dd67232b3bc..c47151495b6f 100644
> --- a/drivers/media/platform/ti-vpe/vpe.c
> +++ b/drivers/media/platform/ti-vpe/vpe.c
> @@ -1597,6 +1597,7 @@ static int __vpe_try_fmt(struct vpe_ctx *ctx, struct v4l2_format *f,
>  	struct v4l2_plane_pix_format *plane_fmt;
>  	unsigned int w_align;
>  	int i, depth, depth_bytes, height;
> +	unsigned int stride = 0;
>  
>  	if (!fmt || !(fmt->types & type)) {
>  		vpe_err(ctx->dev, "Fourcc format (0x%08x) invalid.\n",
> @@ -1683,16 +1684,27 @@ static int __vpe_try_fmt(struct vpe_ctx *ctx, struct v4l2_format *f,
>  		plane_fmt = &pix->plane_fmt[i];
>  		depth = fmt->vpdma_fmt[i]->depth;
>  
> -		if (i == VPE_LUMA)
> -			plane_fmt->bytesperline = (pix->width * depth) >> 3;
> -		else
> -			plane_fmt->bytesperline = pix->width;
> +		stride = (pix->width * fmt->vpdma_fmt[VPE_LUMA]->depth) >> 3;
> +		if (stride > plane_fmt->bytesperline)
> +			plane_fmt->bytesperline = stride;

The old code calculates different bytes per line for luma and chroma,
but the new one calculates only for luma. Is that correct?

 Tomi



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