media: v4l2-core: Introduce v4l2-isp.c

Add to the V4L2 framework helper functions to support drivers when
validating a buffer of V4L2 ISP parameters.

Driver shall use v4l2_isp_params_validate_buffer_size() to verify the
size correctness of the data received from userspace, and after having
copied the data to a kernel-only memory location, complete the
validation by calling v4l2_isp_params_validate_buffer().

Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Michael Riesch <michael.riesch@collabora.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

include/media/v4l2-isp.h

@@ -0,0 +1,91 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Video4Linux2 generic ISP parameters and statistics support
+ *
+ * Copyright (C) 2025 Ideas On Board Oy
+ * Author: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
+ */
+
+#ifndef _V4L2_ISP_H_
+#define _V4L2_ISP_H_
+
+#include <linux/media/v4l2-isp.h>
+
+struct device;
+struct vb2_buffer;
+
+/**
+ * v4l2_isp_params_buffer_size - Calculate size of v4l2_isp_params_buffer
+ * @max_params_size: The total size of the ISP configuration blocks
+ *
+ * Users of the v4l2 extensible parameters will have differing sized data arrays
+ * depending on their specific parameter buffers. Drivers and userspace will
+ * need to be able to calculate the appropriate size of the struct to
+ * accommodate all ISP configuration blocks provided by the platform.
+ * This macro provides a convenient tool for the calculation.
+ */
+#define v4l2_isp_params_buffer_size(max_params_size) \
+	(offsetof(struct v4l2_isp_params_buffer, data) + (max_params_size))
+
+/**
+ * v4l2_isp_params_validate_buffer_size - Validate a V4L2 ISP buffer sizes
+ * @dev: the driver's device pointer
+ * @vb: the videobuf2 buffer
+ * @max_size: the maximum allowed buffer size
+ *
+ * This function performs validation of the size of a V4L2 ISP parameters buffer
+ * before the driver can access the actual data buffer content.
+ *
+ * After the sizes validation, drivers should copy the buffer content to a
+ * kernel-only memory area to prevent userspace from modifying it,
+ * before completing validation using v4l2_isp_params_validate_buffer().
+ *
+ * The @vb buffer as received from the vb2 .buf_prepare() operation is checked
+ * against @max_size and it's validated to be large enough to accommodate at
+ * least one ISP configuration block.
+ */
+int v4l2_isp_params_validate_buffer_size(struct device *dev,
+					 struct vb2_buffer *vb,
+					 size_t max_size);
+
+/**
+ * struct v4l2_isp_params_block_info - V4L2 ISP per-block info
+ * @size: the block expected size
+ *
+ * The v4l2_isp_params_block_info collects information of the ISP configuration
+ * blocks for validation purposes. It currently only contains the expected
+ * block size.
+ *
+ * Drivers shall prepare a list of block info, indexed by block type, one for
+ * each supported ISP block and correctly populate them with the expected block
+ * size.
+ */
+struct v4l2_isp_params_block_info {
+	size_t size;
+};
+
+/**
+ * v4l2_isp_params_validate_buffer - Validate a V4L2 ISP parameters buffer
+ * @dev: the driver's device pointer
+ * @vb: the videobuf2 buffer
+ * @buffer: the V4L2 ISP parameters buffer
+ * @info: the list of per-block validation info
+ * @num_blocks: the number of blocks
+ *
+ * This function completes the validation of a V4L2 ISP parameters buffer,
+ * verifying each configuration block correctness before the driver can use
+ * them to program the hardware.
+ *
+ * Drivers should use this function after having validated the correctness of
+ * the vb2 buffer sizes by using the v4l2_isp_params_validate_buffer_size()
+ * helper first. Once the buffer size has been validated, drivers should
+ * perform a copy of the user provided buffer into a kernel-only memory buffer
+ * to prevent userspace from modifying its content after it has been submitted
+ * to the driver, and then call this function to complete validation.
+ */
+int v4l2_isp_params_validate_buffer(struct device *dev, struct vb2_buffer *vb,
+				    const struct v4l2_isp_params_buffer *buffer,
+				    const struct v4l2_isp_params_block_info *info,
+				    size_t num_blocks);
+
+#endif /* _V4L2_ISP_H_ */