Re: [PATCH v3 2/4] media: v4l2-common: Add v4l2_fill_pixfmt_aligned() helper

Hi Tommaso

On Wed, Jul 08, 2026 at 06:14:03PM +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 <[email protected]>
> ---
> v2->v3:
>  - No changes, just moved to from PATCH 3/4 to PATCH 2/4
>
> v1->v2:
>  - Move v4l2_fill_pixfmt() into v4l2-common.h as inline wrapper
>  - Add v4l2_fill_pixfmt_aligned() helper documentation.
>
>  drivers/media/v4l2-core/v4l2-common.c | 12 +++++----
>  include/media/v4l2-common.h           | 38 +++++++++++++++++++++++++--
>  2 files changed, 43 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
> index 54995ba8c20d..2ce4f1c20fbc 100644
> --- a/drivers/media/v4l2-core/v4l2-common.c
> +++ b/drivers/media/v4l2-core/v4l2-common.c
> @@ -537,8 +537,8 @@ int v4l2_fill_pixfmt_mp_aligned(struct v4l2_pix_format_mplane *pixfmt,
>  }
>  EXPORT_SYMBOL_GPL(v4l2_fill_pixfmt_mp_aligned);
>
> -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;
> @@ -554,15 +554,17 @@ 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);
> +EXPORT_SYMBOL_GPL(v4l2_fill_pixfmt_aligned);
>
>  #ifdef CONFIG_MEDIA_CONTROLLER
>  static s64 v4l2_get_link_freq_ctrl(struct v4l2_ctrl_handler *handler,
> diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h
> index 749fe38c134e..be4dd9762196 100644
> --- a/include/media/v4l2-common.h
> +++ b/include/media/v4l2-common.h
> @@ -554,8 +554,42 @@ static inline bool v4l2_is_format_bayer(const struct v4l2_format_info *f)
>  const struct v4l2_format_info *v4l2_format_info(u32 format);
>  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);
> +
> +/**
> + * v4l2_fill_pixfmt_aligned - Fill in a &struct v4l2_pix_format with stride
> + *	alignment requirements.

nit:
I was about to suggest "No '.' at the end of the function's brief to
match the existing style" but I see the devm_v4l2_sensor_clk_get_legacy
has it. However the majority of the other functions don't, so maybe
consider dropping it.

> + *
> + * @pixfmt: pointer to the &struct v4l2_pix_format to be filled
> + * @pixelformat: the V4L2 pixel format (V4L2_PIX_FMT_*)
> + * @width: image width in pixels
> + * @height: image height in pixels
> + * @stride_alignment: stride alignment in bytes, must be a power of 2
> + *
> + * Fills all fields of @pixfmt for the given pixel format, dimensions, and
> + * stride alignment. Only formats stored in a single memory plane are
> + * supported; returns -EINVAL for multi-memory-plane formats.
> + *
> + * @pixfmt->bytesperline is set to the stride of the primary (plane 0) plane,
> + * rounded up to a multiple of @stride_alignment. For formats that store
> + * multiple component planes in a single memory buffer (e.g. NV12), the
> + * alignment applied to each component plane's stride is scaled relative to
> + * @stride_alignment so that the chroma stride remains consistently derivable

Does this rather mean that

"For formats that store multiple component planes in a single memory
buffer (e.g. NV12), the alignment applied to each component plane is
the first plane @stride_alignment scaled by the plane's sub-sampling
ratio" or have I mis-read this ?

> + * from the luma stride. @pixfmt->bytesperline therefore reflects only the
> + * primary plane stride.
> + *
> + * @pixfmt->sizeimage is set to the total size in bytes of all component planes.

maybe s/component // ?

> + *
> + * Return: 0 on success, -EINVAL if @pixelformat is unknown or uses multiple
> + *	memory planes.

Do you need this tab ?

> + */
> +int v4l2_fill_pixfmt_aligned(struct v4l2_pix_format *pixfmt, u32 pixelformat,
> +			     u32 width, u32 height, u8 stride_alignment);
> +
> +static inline 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);
> +}

All minors or nit-picking
Reviewed-by: Jacopo Mondi <[email protected]>

Thanks
  j

>
>  /* @stride_alignment is a power of 2 value in bytes */
>  int v4l2_fill_pixfmt_mp_aligned(struct v4l2_pix_format_mplane *pixfmt,
> --
> 2.54.0
>
>