Re: [PATCH 1/2] media: v4l2-common: add v4l2_fill_pixfmt_aligned() helper

[Laurent Pinchart]

Hi Tommaso,

Thank you for the patch.

On Wed, Jun 24, 2026 at 12:41:30PM +0200, Tommaso Merciai wrote:
> Add v4l2_fill_pixfmt_aligned(), a variant of v4l2_fill_pixfmt()
> that accepts a stride_alignment parameter, mirroring the existing
> v4l2_fill_pixfmt_mp() / v4l2_fill_pixfmt_mp_aligned() pair.
> 
> v4l2_fill_pixfmt() is refactored to call v4l2_fill_pixfmt_aligned()
> with stride_alignment=1, preserving its existing behaviour.
> 
> The new helper is needed by drivers whose DMA engine requires the
> line stride to be a multiple of a specific value, such as the
> Renesas RZ/G3E CRU which requires 128-byte alignment.
> 
> Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@xxxxxxxxxxxxxx>
> ---
>  drivers/media/v4l2-core/v4l2-common.c | 17 +++++++++++++----
>  include/media/v4l2-common.h           |  3 +++
>  2 files changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
> index 65db7340ad38..1de246acc7ab 100644
> --- a/drivers/media/v4l2-core/v4l2-common.c
> +++ b/drivers/media/v4l2-core/v4l2-common.c
> @@ -545,8 +545,8 @@ int v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane *pixfmt,
>  }
>  EXPORT_SYMBOL_GPL(v4l2_fill_pixfmt_mp);
>  
> -int v4l2_fill_pixfmt(struct v4l2_pix_format *pixfmt, u32 pixelformat,
> -		     u32 width, u32 height)
> +int v4l2_fill_pixfmt_aligned(struct v4l2_pix_format *pixfmt, u32 pixelformat,
> +			     u32 width, u32 height, u8 stride_alignment)
>  {
>  	const struct v4l2_format_info *info;
>  	int i;
> @@ -562,14 +562,23 @@ int v4l2_fill_pixfmt(struct v4l2_pix_format *pixfmt, u32 pixelformat,
>  	pixfmt->width = width;
>  	pixfmt->height = height;
>  	pixfmt->pixelformat = pixelformat;
> -	pixfmt->bytesperline = v4l2_format_plane_stride(info, 0, width, 1);
> +	pixfmt->bytesperline = v4l2_format_plane_stride(info, 0, width,
> +							stride_alignment);
>  	pixfmt->sizeimage = 0;
>  
>  	for (i = 0; i < info->comp_planes; i++)
>  		pixfmt->sizeimage +=
> -			v4l2_format_plane_size(info, i, width, height, 1);
> +			v4l2_format_plane_size(info, i, width, height,
> +					       stride_alignment);
>  	return 0;
>  }
> +EXPORT_SYMBOL_GPL(v4l2_fill_pixfmt_aligned);
> +
> +int v4l2_fill_pixfmt(struct v4l2_pix_format *pixfmt, u32 pixelformat,
> +		     u32 width, u32 height)
> +{
> +	return v4l2_fill_pixfmt_aligned(pixfmt, pixelformat, width, height, 1);
> +}

This could be an inline wrapper in include/media/v4l2-common.h, it would
be more efficient.

>  EXPORT_SYMBOL_GPL(v4l2_fill_pixfmt);
>  
>  #ifdef CONFIG_MEDIA_CONTROLLER
> diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h
> index edd416178c33..718a0f47f36b 100644
> --- a/include/media/v4l2-common.h
> +++ b/include/media/v4l2-common.h
> @@ -556,6 +556,9 @@ void v4l2_apply_frmsize_constraints(u32 *width, u32 *height,
>  				    const struct v4l2_frmsize_stepwise *frmsize);
>  int v4l2_fill_pixfmt(struct v4l2_pix_format *pixfmt, u32 pixelformat,
>  		     u32 width, u32 height);
> +/* @stride_alignment is a power of 2 value in bytes */
> +int v4l2_fill_pixfmt_aligned(struct v4l2_pix_format *pixfmt, u32 pixelformat,
> +			     u32 width, u32 height, u8 stride_alignment);

I know the existing functions lack documentation, but it's not a reason
to continue with that bad habit :-)

One point that needs to be clearly documented is how the stride
alignment is handled for different planes.

>  int v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane *pixfmt, u32 pixelformat,
>  			u32 width, u32 height);
>  /* @stride_alignment is a power of 2 value in bytes */

-- 
Regards,

Laurent Pinchart