[PATCH v6 05/28] media: v4l2-common: add v4l2_fill_pixfmt_mp_aligned helper

["Sven Püschel" <s.pueschel@pengutronix.de>]

Add a v4l2_fill_pixfmt_mp_aligned helper which allows the user to
specify a custom stride alignment in bytes. This is necessary for
hardware like the Rockchip RGA3, which requires the stride value to be
aligned to a 16 bytes boundary.

The code makes some assumptions about the v4l2 format to simplify the
calculation. They currently hold for all known v4l2 formats.

v4l2_format_plane_stride uses an unsigned int as argument type to avoid
the later multiplication from overflowing the u8 value. All other places
use u8, as no practical use cases for a larger alignment are known at
the moment.

Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Sven Püschel <s.pueschel@pengutronix.de>

---
Changes in v6:
- Fixed alignment multiplication of 0 for NV24 - flagged by Sashiko:
  https://sashiko.dev/#/patchset/20260428-spu-rga3-v5-0-eb7f5d019d86%40pengutronix.de?part=5
- Changed v4l2_format_plane_stride alignment parameter type to
  avoid overflow for 64/128 byte alignment by multiplication.
  Flagged by Sashiko URL above.
---
 drivers/media/v4l2-core/v4l2-common.c | 51 ++++++++++++++++++++++++++---------
 include/media/v4l2-common.h           |  4 +++
 2 files changed, 43 insertions(+), 12 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
index 3cc8b04e1ea63..a03e48812bcf5 100644
--- a/drivers/media/v4l2-core/v4l2-common.c
+++ b/drivers/media/v4l2-core/v4l2-common.c
@@ -432,14 +432,28 @@ static inline unsigned int v4l2_format_block_height(const struct v4l2_format_inf
 }
 
 static inline unsigned int v4l2_format_plane_stride(const struct v4l2_format_info *info, int plane,
-						    unsigned int width)
+						    unsigned int width, unsigned int byte_alignment)
 {
 	unsigned int hdiv = plane ? info->hdiv : 1;
 	unsigned int aligned_width =
 		ALIGN(width, v4l2_format_block_width(info, plane));
 
-	return DIV_ROUND_UP(aligned_width, hdiv) *
-	       info->bpp[plane] / info->bpp_div[plane];
+	/*
+	 * Formats with a single memory plane derive the stride of the
+	 * other planes from the y stride. Due to chroma subsampling this
+	 * may cause the other plane strides to break the byte_alignment.
+	 * Increase the alignment if necessary to prevent this.
+	 *
+	 * It assumes the following format properties:
+	 * - bpp_div[0] == bpp_div[1]
+	 * - The multiplication factor doesn't differ between the non y planes
+	 */
+	if (info->mem_planes == 1 && info->comp_planes > 1 && plane == 0)
+		byte_alignment *= DIV_ROUND_UP(info->hdiv * info->bpp[0], info->bpp[1]);
+
+	return ALIGN(DIV_ROUND_UP(aligned_width, hdiv) * info->bpp[plane] /
+			     info->bpp_div[plane],
+		     byte_alignment);
 }
 
 static inline unsigned int v4l2_format_plane_height(const struct v4l2_format_info *info, int plane,
@@ -453,9 +467,10 @@ static inline unsigned int v4l2_format_plane_height(const struct v4l2_format_inf
 }
 
 static inline unsigned int v4l2_format_plane_size(const struct v4l2_format_info *info, int plane,
-						  unsigned int width, unsigned int height)
+						  unsigned int width, unsigned int height,
+						  u8 stride_alignment)
 {
-	return v4l2_format_plane_stride(info, plane, width) *
+	return v4l2_format_plane_stride(info, plane, width, stride_alignment) *
 	       v4l2_format_plane_height(info, plane, height);
 }
 
@@ -476,8 +491,9 @@ void v4l2_apply_frmsize_constraints(u32 *width, u32 *height,
 }
 EXPORT_SYMBOL_GPL(v4l2_apply_frmsize_constraints);
 
-int v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane *pixfmt,
-			u32 pixelformat, u32 width, u32 height)
+int v4l2_fill_pixfmt_mp_aligned(struct v4l2_pix_format_mplane *pixfmt,
+				u32 pixelformat, u32 width, u32 height,
+				u8 stride_alignment)
 {
 	const struct v4l2_format_info *info;
 	struct v4l2_plane_pix_format *plane;
@@ -494,23 +510,34 @@ int v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane *pixfmt,
 
 	if (info->mem_planes == 1) {
 		plane = &pixfmt->plane_fmt[0];
-		plane->bytesperline = v4l2_format_plane_stride(info, 0, width);
+		plane->bytesperline = v4l2_format_plane_stride(info, 0, width,
+							       stride_alignment);
 		plane->sizeimage = 0;
 
 		for (i = 0; i < info->comp_planes; i++)
 			plane->sizeimage +=
-				v4l2_format_plane_size(info, i, width, height);
+				v4l2_format_plane_size(info, i, width, height,
+						       stride_alignment);
 	} else {
 		for (i = 0; i < info->comp_planes; i++) {
 			plane = &pixfmt->plane_fmt[i];
 			plane->bytesperline =
-				v4l2_format_plane_stride(info, i, width);
+				v4l2_format_plane_stride(info, i, width,
+							 stride_alignment);
 			plane->sizeimage = plane->bytesperline *
 				v4l2_format_plane_height(info, i, height);
 		}
 	}
 	return 0;
 }
+EXPORT_SYMBOL_GPL(v4l2_fill_pixfmt_mp_aligned);
+
+int v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane *pixfmt,
+			u32 pixelformat, u32 width, u32 height)
+{
+	return v4l2_fill_pixfmt_mp_aligned(pixfmt, pixelformat,
+					   width, height, 1);
+}
 EXPORT_SYMBOL_GPL(v4l2_fill_pixfmt_mp);
 
 int v4l2_fill_pixfmt(struct v4l2_pix_format *pixfmt, u32 pixelformat,
@@ -530,12 +557,12 @@ 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);
+	pixfmt->bytesperline = v4l2_format_plane_stride(info, 0, width, 1);
 	pixfmt->sizeimage = 0;
 
 	for (i = 0; i < info->comp_planes; i++)
 		pixfmt->sizeimage +=
-			v4l2_format_plane_size(info, i, width, height);
+			v4l2_format_plane_size(info, i, width, height, 1);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(v4l2_fill_pixfmt);
diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h
index 401d8506c24b5..edd416178c333 100644
--- a/include/media/v4l2-common.h
+++ b/include/media/v4l2-common.h
@@ -558,6 +558,10 @@ int v4l2_fill_pixfmt(struct v4l2_pix_format *pixfmt, u32 pixelformat,
 		     u32 width, u32 height);
 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 */
+int v4l2_fill_pixfmt_mp_aligned(struct v4l2_pix_format_mplane *pixfmt,
+				u32 pixelformat, u32 width, u32 height,
+				u8 stride_alignment);
 
 /**
  * v4l2_get_link_freq - Get link rate from transmitter

-- 
2.54.0