media: hevc: add bounded tile-count helpers

The stateless HEVC decoders compute the number of tile columns and rows
from num_tile_columns_minus1 / num_tile_rows_minus1 and clamp it to the
column_width_minus1[] / row_height_minus1[] capacity before using it as a
loop bound. Add shared helpers in a new <media/v4l2-hevc.h> so the rkvdec
and hantro drivers do not each open-code the min_t() clamp.

Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Assisted-by: Claude:claude-opus-4-8
Fixes: 256fa3920874 ("media: v4l: Add definitions for HEVC stateless decoding")
Cc: stable@vger.kernel.org
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

1 files changed, 41 insertions, 0 deletions

diff --git a/include/media/v4l2-hevc.h b/include/media/v4l2-hevc.h
new file mode 100644
index 000000000000..973c96be16be
--- /dev/null
+++ b/include/media/v4l2-hevc.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Helper functions for HEVC stateless codecs.
+ */
+
+#ifndef _MEDIA_V4L2_HEVC_H
+#define _MEDIA_V4L2_HEVC_H
+
+#include <linux/minmax.h>
+#include <media/v4l2-ctrls.h>
+
+/**
+ * v4l2_hevc_pps_num_tile_columns - number of HEVC tile columns, bounded
+ * @pps: the V4L2 HEVC PPS control
+ *
+ * Return the number of tile columns (num_tile_columns_minus1 + 1) clamped to
+ * the capacity of column_width_minus1[]. The control validation already
+ * rejects out-of-range counts; this keeps the consuming drivers bounded too.
+ */
+static inline unsigned int
+v4l2_hevc_pps_num_tile_columns(const struct v4l2_ctrl_hevc_pps *pps)
+{
+	return min_t(unsigned int, pps->num_tile_columns_minus1 + 1,
+		     ARRAY_SIZE(pps->column_width_minus1));
+}
+
+/**
+ * v4l2_hevc_pps_num_tile_rows - number of HEVC tile rows, bounded
+ * @pps: the V4L2 HEVC PPS control
+ *
+ * Return the number of tile rows (num_tile_rows_minus1 + 1) clamped to the
+ * capacity of row_height_minus1[].
+ */
+static inline unsigned int
+v4l2_hevc_pps_num_tile_rows(const struct v4l2_ctrl_hevc_pps *pps)
+{
+	return min_t(unsigned int, pps->num_tile_rows_minus1 + 1,
+		     ARRAY_SIZE(pps->row_height_minus1));
+}
+
+#endif /* _MEDIA_V4L2_HEVC_H */