Re: [PATCH v2] media: rcar-isp: ispcore: Fix inconsistent step sizes

[Jacopo Mondi <jacopo.mondi@ideasonboard.com>]

Hi Barnabás

On Thu, Oct 01, 2026 at 10:51:30AM +0200, Barnabás Pőcze wrote:
> `risp_io_{input,capture}_enum_framesizes()` sets the horizontal and vertical
> step size to 2. However, `risp_io_{input,capture}_try_format()` passes 2
> to `v4l_bound_align_image()`, which corresponds to a step size of 2^2 = 4.
>
> So move these constants into macros to avoid the repetition, and with that,
> use 4 as the step size everywhere.

Why 4 ?

I can't find any such limit in documentation.

For input I don't find alignment constraints nor in CS or VSPX
documentation.

For output I only see a requirement that the stride is 256 bits
aligned, something that is enforced by risp_io_capture_try_format()
already.

I see Niklas has reviewed the patch, so he might have found somewhere
in the long documentation where the alignment for both input and
capture nodes is described.

>
> Fixes: 2151350f60d1 ("media: rcar-isp: Add support for ISPCORE")
> Signed-off-by: Barnabás Pőcze <barnabas.pocze+renesas@ideasonboard.com>
> Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> ---
> changes in v2:
>   * fix typo
>
> v1: https://lore.kernel.org/linux-media/20260929133020.342677-2-barnabas.pocze+renesas@ideasonboard.com
> ---
>  .../media/platform/renesas/rcar-isp/core-io.c | 40 +++++++++++--------
>  1 file changed, 24 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/media/platform/renesas/rcar-isp/core-io.c b/drivers/media/platform/renesas/rcar-isp/core-io.c
> index 820af506f896c..b60b91f43d42d 100644
> --- a/drivers/media/platform/renesas/rcar-isp/core-io.c
> +++ b/drivers/media/platform/renesas/rcar-isp/core-io.c
> @@ -15,6 +15,12 @@
>
>  #include "risp-core.h"
>
> +#define RISP_MIN_WIDTH 128
> +#define RISP_MAX_WIDTH 5120
> +#define RISP_MIN_HEIGHT 128
> +#define RISP_MAX_HEIGHT 4096
> +#define RISP_SIZE_ALIGNMENT 2 /* 2^2 = 4 */

The fact that 2 means 2^2 is only because of how
v4l_bound_align_image() is implemented

> +
>  #define risp_io_err(d, fmt, arg...)         dev_err((d)->core->dev, fmt, ##arg)
>
>  static struct risp_buffer *risp_io_vb2buf(struct vb2_v4l2_buffer *vb)
> @@ -330,8 +336,9 @@ static void risp_io_input_try_format(struct rcar_isp_core_io *io,
>  {
>  	unsigned int bpp = 0;
>
> -	v4l_bound_align_image(&pix->width, 128, 5120, 2,
> -			      &pix->height, 128, 4096, 2, 0);
> +	v4l_bound_align_image(&pix->width, RISP_MIN_WIDTH, RISP_MAX_WIDTH, RISP_SIZE_ALIGNMENT,
> +			      &pix->height, RISP_MIN_HEIGHT, RISP_MAX_HEIGHT, RISP_SIZE_ALIGNMENT,

Should we maybe use 1 here, unless it is documented that 4 is a
requirement ?

My suspicion is that we originally meant '2' everywhere, but
v4l_bound_align_image() is weird and if you pass '2' in it means
'2^2' and this went unnoticed.

> +			      0);
>
>  	for (unsigned int i = 0; i < ARRAY_SIZE(risp_io_input_formats); i++) {
>  		if (risp_io_input_formats[i].fourcc == pix->pixelformat) {
> @@ -423,13 +430,13 @@ static int risp_io_input_enum_framesizes(struct file *file, void *fh,
>
>  	fsize->type = V4L2_FRMSIZE_TYPE_STEPWISE;
>
> -	fsize->stepwise.min_width = 128;
> -	fsize->stepwise.max_width = 5120;
> -	fsize->stepwise.step_width = 2;
> +	fsize->stepwise.min_width = RISP_MIN_WIDTH;
> +	fsize->stepwise.max_width = RISP_MAX_WIDTH;
> +	fsize->stepwise.step_width = 1u << RISP_SIZE_ALIGNMENT;
>
> -	fsize->stepwise.min_height = 128;
> -	fsize->stepwise.max_height = 4096;
> -	fsize->stepwise.step_height = 2;
> +	fsize->stepwise.min_height = RISP_MIN_HEIGHT;
> +	fsize->stepwise.max_height = RISP_MAX_HEIGHT;
> +	fsize->stepwise.step_height = 1u << RISP_SIZE_ALIGNMENT;
>
>  	return 0;
>  }
> @@ -720,8 +727,9 @@ static const struct v4l2_pix_format_mplane risp_io_capture_default_format = {
>  static void risp_io_capture_try_format(struct rcar_isp_core_io *io,
>  				       struct v4l2_pix_format_mplane *pix)
>  {
> -	v4l_bound_align_image(&pix->width, 128, 5120, 2,
> -			      &pix->height, 128, 4096, 2, 0);
> +	v4l_bound_align_image(&pix->width, RISP_MIN_WIDTH, RISP_MAX_WIDTH, RISP_SIZE_ALIGNMENT,
> +			      &pix->height, RISP_MIN_HEIGHT, RISP_MAX_HEIGHT, RISP_SIZE_ALIGNMENT,
> +			      0);
>
>  	pix->field = V4L2_FIELD_NONE;
>  	pix->colorspace = V4L2_COLORSPACE_SRGB;
> @@ -824,13 +832,13 @@ static int risp_io_capture_enum_framesizes(struct file *file, void *fh,
>
>  	fsize->type = V4L2_FRMSIZE_TYPE_STEPWISE;
>
> -	fsize->stepwise.min_width = 128;
> -	fsize->stepwise.max_width = 5120;
> -	fsize->stepwise.step_width = 2;
> +	fsize->stepwise.min_width = RISP_MIN_WIDTH;
> +	fsize->stepwise.max_width = RISP_MAX_WIDTH;
> +	fsize->stepwise.step_width = 1u << RISP_SIZE_ALIGNMENT;
>
> -	fsize->stepwise.min_height = 128;
> -	fsize->stepwise.max_height = 4096;
> -	fsize->stepwise.step_height = 2;
> +	fsize->stepwise.min_height = RISP_MIN_HEIGHT;
> +	fsize->stepwise.max_height = RISP_MAX_HEIGHT;
> +	fsize->stepwise.step_height = 1u << RISP_SIZE_ALIGNMENT;
>
>  	return 0;
>  }
> --
> 2.55.0
>
>