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

[Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>]

Hi Laurent,
Thanks for your review.

On Wed, Jun 24, 2026 at 10:28:55PM +0300, Laurent Pinchart wrote:
> 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@bp.renesas.com>
> > ---
> >  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.

Ok, thanks.
I guess we want the same for v4l2_fill_pixfmt_mp() ?

> 
> >  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 :-)

Ouch :)

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

Thanks, I will add documentation in v2.


Kind Regards,
Tommaso

> 
> >  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