Re: [PATCH v8 5/8] media: v4l2-core: Introduce v4l2-isp.c

[Antoine Bouyer <antoine.bouyer@nxp.com>]

Hi Jacopo

On 10/20/25 10:24 AM, Jacopo Mondi wrote:
> 
> 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>
> Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
> ---
>   MAINTAINERS                        |   2 +
>   drivers/media/v4l2-core/Kconfig    |   4 ++
>   drivers/media/v4l2-core/Makefile   |   1 +
>   drivers/media/v4l2-core/v4l2-isp.c | 128 +++++++++++++++++++++++++++++++++++++
>   include/media/v4l2-isp.h           |  91 ++++++++++++++++++++++++++
>   5 files changed, 226 insertions(+)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index f52237d57710cadff78b297d2b4610b508f55092..5833f82caa7f2f734bb0e1be144ade2109b23988 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -26857,6 +26857,8 @@ M:      Jacopo Mondi <jacopo.mondi@ideasonboard.com>
>   L:     linux-media@vger.kernel.org
>   S:     Maintained
>   F:     Documentation/userspace-api/media/v4l/v4l2-isp.rst
> +F:     drivers/media/v4l2-core/v4l2-isp.c
> +F:     include/media/v4l2-isp.h
>   F:     include/uapi/linux/media/v4l2-isp.h
> 
>   VF610 NAND DRIVER
> diff --git a/drivers/media/v4l2-core/Kconfig b/drivers/media/v4l2-core/Kconfig
> index 331b8e535e5bbf33f22638b2ae8bc764ad5fc407..d50ccac9733cc39a43426ae7e7996dd0b5b45186 100644
> --- a/drivers/media/v4l2-core/Kconfig
> +++ b/drivers/media/v4l2-core/Kconfig
> @@ -82,3 +82,7 @@ config V4L2_CCI_I2C
>          depends on I2C
>          select REGMAP_I2C
>          select V4L2_CCI
> +
> +config V4L2_ISP
> +       tristate

When configured as module, there's build error:

ERROR: modpost: missing MODULE_LICENSE() in 
drivers/media/v4l2-core/v4l2-isp.o
WARNING: modpost: missing MODULE_DESCRIPTION() in 
drivers/media/v4l2-core/v4l2-isp.o

It happens when selected from an ISP driver, and ISP driver is a module. 
Then module is applied to v4l2-isp too.

> +       depends on VIDEOBUF2_CORE
> diff --git a/drivers/media/v4l2-core/Makefile b/drivers/media/v4l2-core/Makefile
> index 2177b9d63a8ffc1127c5a70118249a2ff63cd759..329f0eadce994cc1c8580beb435f68fa7e2a7aeb 100644
> --- a/drivers/media/v4l2-core/Makefile
> +++ b/drivers/media/v4l2-core/Makefile
> @@ -29,6 +29,7 @@ obj-$(CONFIG_V4L2_CCI) += v4l2-cci.o
>   obj-$(CONFIG_V4L2_FLASH_LED_CLASS) += v4l2-flash-led-class.o
>   obj-$(CONFIG_V4L2_FWNODE) += v4l2-fwnode.o
>   obj-$(CONFIG_V4L2_H264) += v4l2-h264.o
> +obj-$(CONFIG_V4L2_ISP) += v4l2-isp.o
>   obj-$(CONFIG_V4L2_JPEG_HELPER) += v4l2-jpeg.o
>   obj-$(CONFIG_V4L2_MEM2MEM_DEV) += v4l2-mem2mem.o
>   obj-$(CONFIG_V4L2_VP9) += v4l2-vp9.o
> diff --git a/drivers/media/v4l2-core/v4l2-isp.c b/drivers/media/v4l2-core/v4l2-isp.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..35f0b701f1729c3c0ccc34b1c89189b179e0b684
> --- /dev/null
> +++ b/drivers/media/v4l2-core/v4l2-isp.c
> @@ -0,0 +1,128 @@
> +// 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>
> + */
> +
> +#include <media/v4l2-isp.h>
> +
> +#include <linux/bitops.h>
> +#include <linux/device.h>
> +
> +#include <media/videobuf2-core.h>
> +
> +int v4l2_isp_params_validate_buffer_size(struct device *dev,
> +                                        struct vb2_buffer *vb,
> +                                        size_t max_size)
> +{
> +       size_t header_size = offsetof(struct v4l2_isp_params_buffer, data);
> +       size_t payload_size = vb2_get_plane_payload(vb, 0);
> +
> +       /* Payload size can't be greater than the destination buffer size */
> +       if (payload_size > max_size) {
> +               dev_dbg(dev, "Payload size is too large: %zu\n", payload_size);
> +               return -EINVAL;
> +       }
> +
> +       /* Payload size can't be smaller than the header size */
> +       if (payload_size < header_size) {
> +               dev_dbg(dev, "Payload size is too small: %zu\n", payload_size);
> +               return -EINVAL;
> +       }
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_isp_params_validate_buffer_size);
> +
> +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)
> +{
> +       size_t header_size = offsetof(struct v4l2_isp_params_buffer, data);
> +       size_t payload_size = vb2_get_plane_payload(vb, 0);
> +       size_t block_offset = 0;
> +       size_t buffer_size;
> +
> +       /*
> +        * Currently only the first version of the V4L2 ISP parameters format is
> +        * supported. We accept both V0 and V1 to support existing drivers
> +        * compatible with V4L2 ISP that use either 0 or 1 as their "first
> +        * version" identifiers.
> +        */
> +       if (buffer->version != V4L2_ISP_PARAMS_VERSION_V0 &&
> +           buffer->version != V4L2_ISP_PARAMS_VERSION_V1) {
> +               dev_dbg(dev,
> +                       "Unsupported V4L2 ISP parameters format version: %u\n",
> +                       buffer->version);
> +               return -EINVAL;
> +       }
> +
> +       /* Validate the size reported in the header */
> +       buffer_size = header_size + buffer->data_size;
> +       if (buffer_size != payload_size) {
> +               dev_dbg(dev, "Data size %zu and payload size %zu are different\n",
> +                       buffer_size, payload_size);
> +               return -EINVAL;
> +       }
> +
> +       /* Walk the list of ISP configuration blocks and validate them. */
> +       buffer_size = buffer->data_size;
> +       while (buffer_size >= sizeof(struct v4l2_isp_params_block_header)) {
> +               const struct v4l2_isp_params_block_info *block_info;
> +               const struct v4l2_isp_params_block_header *block;
> +
> +               block = (const struct v4l2_isp_params_block_header *)
> +                       (buffer->data + block_offset);
> +
> +               if (block->type >= num_blocks) {
> +                       dev_dbg(dev,
> +                               "Invalid block type %u at offset %zu\n",
> +                               block->type, block_offset);
> +                       return -EINVAL;
> +               }
> +
> +               if (block->size > buffer_size) {
> +                       dev_dbg(dev, "Premature end of parameters data\n");
> +                       return -EINVAL;
> +               }
> +
> +               /* It's invalid to specify both ENABLE and DISABLE. */
> +               if ((block->flags & (V4L2_ISP_PARAMS_FL_BLOCK_ENABLE |
> +                                    V4L2_ISP_PARAMS_FL_BLOCK_DISABLE)) ==
> +                    (V4L2_ISP_PARAMS_FL_BLOCK_ENABLE |
> +                    V4L2_ISP_PARAMS_FL_BLOCK_DISABLE)) {
> +                       dev_dbg(dev, "Invalid block flags %x at offset %zu\n",
> +                               block->flags, block_offset);
> +                       return -EINVAL;
> +               }
> +
> +               /*
> +                * Match the block reported size against the info provided
> +                * one, but allow the block to only contain the header in
> +                * case it is going to be disabled.
> +                */
> +               block_info = &info[block->type];
> +               if (block->size != block_info->size &&
> +                   (!(block->flags & V4L2_ISP_PARAMS_FL_BLOCK_DISABLE) ||
> +                   block->size != sizeof(*block))) {
> +                       dev_dbg(dev,
> +                               "Invalid block size %u (expected %zu) at offset %zu\n",
> +                               block->size, block_info->size, block_offset);
> +                       return -EINVAL;
> +               }
> +
> +               block_offset += block->size;
> +               buffer_size -= block->size;
> +       }
> +
> +       if (buffer_size) {
> +               dev_dbg(dev, "Unexpected data after the parameters buffer end\n");
> +               return -EINVAL;
> +       }
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_isp_params_validate_buffer);
> diff --git a/include/media/v4l2-isp.h b/include/media/v4l2-isp.h
> new file mode 100644
> index 0000000000000000000000000000000000000000..8b4695663699e7f176384739cf54ed7fa2c578f8
> --- /dev/null
> +++ b/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_ */
> 
> --
> 2.51.0
>