Message-ID: <20251006004741.GA29231@pendragon.ideasonboard.com>
Date: Mon, 6 Oct 2025 03:47:41 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Jacopo Mondi <jacopo.mondi@...asonboard.com>
Cc: Dafna Hirschfeld <dafna@...tmail.com>, Keke Li <keke.li@...ogic.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Dan Scally <dan.scally@...asonboard.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Antoine Bouyer <antoine.bouyer@....com>,
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	linux-rockchip@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v5 5/8] media: v4l2-core: Introduce v4l2-isp.c

Hi Jacopo,

Thank you for the patch.

On Mon, Sep 15, 2025 at 07:18:14PM +0200, Jacopo Mondi wrote:
> Add to the v4l2 framework helper functions to support drivers

s/v4l2/V4L2/

> when validating a buffer of extensible ISP parameters.
> 
> Introduce new types in include/media/v4l2-isp.h that drivers shall use
> in order to comply with the generic ISP parameters validation procedure,
> and add helper functionss to v4l2-isp.c to perform blocks and buffer
> validation.
> 
> Reviewed-by: Daniel Scally <dan.scally@...asonboard.com>
> Signed-off-by: Jacopo Mondi <jacopo.mondi@...asonboard.com>
> ---
>  MAINTAINERS                        |   2 +
>  drivers/media/v4l2-core/Kconfig    |   4 ++
>  drivers/media/v4l2-core/Makefile   |   1 +
>  drivers/media/v4l2-core/v4l2-isp.c | 108 +++++++++++++++++++++++++++++++++++++
>  include/media/v4l2-isp.h           | 100 ++++++++++++++++++++++++++++++++++
>  5 files changed, 215 insertions(+)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index abba872cb63f1430a49a2afbace4b9f9958c3991..5e0e4208ebe6c58a9ea0834e1ebb36abd2de06e1 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -26415,6 +26415,8 @@ M:	Jacopo Mondi <jacopo.mondi@...asonboard.com>
>  L:	linux-media@...r.kernel.org
>  S:	Maintained
>  F:	Documentation/userspace-api/media/v4l/extensible-parameters.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
> +	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..e350bdaf53b5502e1ec2a4989c20df1100ab2d2a
> --- /dev/null
> +++ b/drivers/media/v4l2-core/v4l2-isp.c
> @@ -0,0 +1,108 @@
> +// 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@...asonboard.com>
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/device.h>
> +
> +#include <media/videobuf2-core.h>
> +#include <media/v4l2-isp.h>

v4l2-isp goes first.

> +
> +int v4l2_params_buffer_validate(struct device *dev, struct vb2_buffer *vb,
> +				size_t max_size)
> +{
> +	size_t header_size = offsetof(struct v4l2_params_buffer, data);
> +	struct v4l2_params_buffer *buffer = vb2_plane_vaddr(vb, 0);
> +	size_t payload_size = vb2_get_plane_payload(vb, 0);
> +	size_t buffer_size;
> +
> +	/* 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;
> +	}
> +
> +	/* Validate the size reported in the parameter buffer 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;
> +	}

This check needs to go to v4l2_params_blocks_validate() as it has to be
performed on the data after copying.

> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_params_buffer_validate);
> +
> +int v4l2_params_blocks_validate(struct device *dev,
> +				const struct v4l2_params_buffer *buffer,
> +				const struct v4l2_params_handler *handlers,
> +				size_t num_handlers)
> +{
> +	size_t block_offset = 0;
> +	size_t buffer_size;
> +
> +	/* Walk the list of parameter blocks and validate them. */
> +	buffer_size = buffer->data_size;
> +	while (buffer_size >= sizeof(struct v4l2_params_block_header)) {
> +		const struct v4l2_params_handler *handler;
> +		const struct v4l2_params_block_header *block;
> +
> +		/* Validate block sizes and types against the handlers. */
> +		block = (const struct v4l2_params_block_header *)
> +			(buffer->data + block_offset);
> +
> +		if (block->type >= num_handlers) {
> +			dev_dbg(dev, "Invalid parameters block type\n");

I'd print the type and offset in the message to ease debugging.

> +			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_PARAMS_FL_BLOCK_ENABLE |
> +				     V4L2_PARAMS_FL_BLOCK_DISABLE)) ==
> +		     (V4L2_PARAMS_FL_BLOCK_ENABLE |
> +		     V4L2_PARAMS_FL_BLOCK_DISABLE)) {
> +			dev_dbg(dev, "Invalid parameters block flags\n");

Same here (print the flags and offset).

> +			return -EINVAL;
> +		}
> +
> +		/*
> +		 * Match the block reported size against the handler's expected
> +		 * one, but allow the block to only contain the header in
> +		 * case it is going to be disabled.
> +		 */
> +		handler = &handlers[block->type];
> +		if (block->size != handler->size &&
> +		    (!(block->flags & V4L2_PARAMS_FL_BLOCK_DISABLE) ||
> +		    block->size != sizeof(*block))) {
> +			dev_dbg(dev, "Invalid parameters block size\n");

And here too (print the size and 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_params_blocks_validate);
> diff --git a/include/media/v4l2-isp.h b/include/media/v4l2-isp.h
> new file mode 100644
> index 0000000000000000000000000000000000000000..2ad62c6169eef3d0fb8d245de56cc6bd7e6227e4
> --- /dev/null
> +++ b/include/media/v4l2-isp.h
> @@ -0,0 +1,100 @@
> +/* 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@...asonboard.com>
> + */
> +
> +#ifndef V4L2_PARAMS_H_
> +#define V4L2_PARAMS_H_

V4L2_ISP_H_

> +
> +#include <linux/media/v4l2-isp.h>
> +
> +struct device;
> +struct vb2_buffer;
> +
> +/**
> + * typedef v4l2_params_block_handler - V4L2 extensible format block handler

As commented on 1/8, let's use the v4l2_isp_ prefix.

> + * @arg: pointer the driver-specific argument
> + * @block: the ISP configuration block to handle
> + *
> + * Defines the function signature of the functions that handle an ISP block
> + * configuration.
> + */
> +typedef void (*v4l2_params_block_handler)(void *arg,
> +					  const struct v4l2_params_block_header *block);
> +
> +/**
> + * struct v4l2_params_handler - V4L2 extensible format handler
> + * @size: the block expected size
> + * @handler: the block handler function
> + *
> + * The v4l2_params_handler defines the type that driver making use of the
> + * V4L2 extensible parameters shall use to define their own ISP block
> + * handlers.
> + *
> + * Drivers shall prepare a list of handlers, one for each supported ISP block
> + * and correctly populate the structure's field with the expected block @size
> + * (used for validation) and a pointer to each block @handler function.
> + */
> +struct v4l2_params_handler {
> +	size_t size;
> +	v4l2_params_block_handler handler;
> +};
> +
> +/**
> + * v4l2_params_buffer_validate - Validate a V4L2 extensible parameters buffer

As this is the pre-copy validation, what would you think of calling the
function v4l2_isp_params_pre_validate_buffer() ? The next function would
be called v4l2_isp_params_validate_buffer(), as they're both about
buffer validation. I'm also OK to keep the current names (with a
v4l2_isp_ prefix).

I'm also thinking that the copy could be moved to the helper, but it can
be done later.

> + * @dev: the driver's device pointer
> + * @vb: the videobuf2 buffer
> + * @max_size: the maximum allowed buffer size
> + * @buffer_validate: callback to the driver-specific buffer validation

You forgot to drop the documentation for this argument.

> + *
> + * Helper function that performs validation of an extensible parameters buffer.
> + *
> + * The helper is meant to be used by drivers to perform validation of the
> + * extensible parameters buffer size correctness.
> + *
> + * The @vb buffer as received from the vb2 .buf_prepare() operation is checked
> + * against @max_size and its validated to be large enough to accommodate at
> + * least one ISP configuration block. The effective buffer size is compared
> + * with the reported data size to make sure they match.
> + *
> + * Drivers should use this function to validate the buffer size correctness
> + * before performing a copy of the user-provided videobuf2 buffer content into a
> + * kernel-only memory buffer to prevent userspace from modifying the buffer
> + * content after it has been submitted to the driver.
> + */
> +int v4l2_params_buffer_validate(struct device *dev, struct vb2_buffer *vb,
> +				size_t max_size);
> +
> +/**
> + * v4l2_params_blocks_validate - Validate V4L2 extensible parameters ISP
> + *				 configuration blocks
> + * @dev: the driver's device pointer
> + * @buffer: the extensible parameters configuration buffer
> + * @handlers: the list of block handlers

array of block handlers

> + * @num_handlers: the number of block handlers
> + *
> + * Helper function that performs validation of the ISP configuration blocks in
> + * an extensible parameters buffer.
> + *
> + * The helper is meant to be used by drivers to perform validation of the
> + * ISP configuration data blocks. For each block in the extensible parameters
> + * buffer, its size and correctness are validated against its associated handler
> + * in the @handlers list.

You need to explain somewhere that the handlers array is indexed by
block type.

> + *
> + * Drivers should use this function to validate the ISP configuration blocks
> + * after having validated the correctness of the vb2 buffer sizes by using the
> + * v4l2_params_buffer_validate() 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 the buffer
> + * content after it has been submitted to the driver, and then call this
> + * function to perform per-block validation.

There's room for improvement in the documentation. I think it would be
clearer if you explained the big picture in
Documentation/userspace-api/media/v4l/extensible-parameters.rst
(pre-validation, copy and post-validation), and only focussed on what
those two functions do in their kerneldoc. That can be done later,
nothing that you say here is incorrect.

With the other comments addressed,

Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>

> + */
> +int v4l2_params_blocks_validate(struct device *dev,
> +				const struct v4l2_params_buffer *buffer,
> +				const struct v4l2_params_handler *handlers,
> +				size_t num_handlers);
> +
> +#endif /* V4L2_PARAMS_H_ */

-- 
Regards,

Laurent Pinchart

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