Re: [PATCH v2 3/8] media: uapi: Convert Amlogic C3 to V4L2 extensible params

[Dan Scally <dan.scally@ideasonboard.com>]

Hi Jacopo

On 10/07/2025 14:52, Jacopo Mondi wrote:
> With the introduction of common types for extensible parameters
> format, convert the c3-isp-config.h header to use the new types.
>
> Factor-out the documentation that is now part of the common header
> and only keep the driver-specific on in place.
>
> The conversion to use common types doesn't impact userspace as the
> new types are either identical to the ones already existing in the
> C3 ISP uAPI or are 1-to-1 type convertible.
>
> Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>

Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>

> ---
>   include/uapi/linux/media/amlogic/c3-isp-config.h | 48 ++++++++----------------
>   1 file changed, 15 insertions(+), 33 deletions(-)
>
> diff --git a/include/uapi/linux/media/amlogic/c3-isp-config.h b/include/uapi/linux/media/amlogic/c3-isp-config.h
> index ed085ea62a574932c7ad8d59d34b2c5c74a597d8..15d3ac289ece610132e1d4b43ecd56b7ef527ef6 100644
> --- a/include/uapi/linux/media/amlogic/c3-isp-config.h
> +++ b/include/uapi/linux/media/amlogic/c3-isp-config.h
> @@ -6,8 +6,13 @@
>   #ifndef _UAPI_C3_ISP_CONFIG_H_
>   #define _UAPI_C3_ISP_CONFIG_H_
>   
> +#ifdef __KERNEL__
> +#include <linux/build_bug.h>
> +#endif /* __KERNEL__ */
>   #include <linux/types.h>
>   
> +#include <linux/media/v4l2-extensible-params.h>
> +
>   /*
>    * Frames are split into zones of almost equal width and height - a zone is a
>    * rectangular tile of a frame. The metering blocks within the ISP collect
> @@ -183,11 +188,6 @@ enum c3_isp_params_block_type {
>    * struct c3_isp_params_block_header - C3 ISP parameter block header
>    *
>    * This structure represents the common part of all the ISP configuration
> - * blocks. Each parameters block shall embed an instance of this structure type
> - * as its first member, followed by the block-specific configuration data. The
> - * driver inspects this common header to discern the block type and its size and
> - * properly handle the block content by casting it to the correct block-specific
> - * type.
>    *
>    * The @type field is one of the values enumerated by
>    * :c:type:`c3_isp_params_block_type` and specifies how the data should be
> @@ -223,15 +223,8 @@ enum c3_isp_params_block_type {
>    *			gamma->pst_gamma_lut[i] = i;
>    *	}
>    *
> - * @type: The parameters block type from :c:type:`c3_isp_params_block_type`
> - * @flags: A bitmask of block flags
> - * @size: Size (in bytes) of the parameters block, including this header
>    */
> -struct c3_isp_params_block_header {
> -	__u16 type;
> -	__u16 flags;
> -	__u32 size;
> -};
> +#define c3_isp_params_block_header v4l2_params_block_header
>   
>   /**
>    * struct c3_isp_params_awb_gains - Gains for auto-white balance
> @@ -498,26 +491,9 @@ struct c3_isp_params_blc {
>   /**
>    * struct c3_isp_params_cfg - C3 ISP configuration parameters
>    *
> - * This struct contains the configuration parameters of the C3 ISP
> - * algorithms, serialized by userspace into an opaque data buffer. Each
> - * configuration parameter block is represented by a block-specific structure
> - * which contains a :c:type:`c3_isp_param_block_header` entry as first
> - * member. Userspace populates the @data buffer with configuration parameters
> - * for the blocks that it intends to configure. As a consequence, the data
> - * buffer effective size changes according to the number of ISP blocks that
> - * userspace intends to configure.
> - *
> - * The parameters buffer is versioned by the @version field to allow modifying
> - * and extending its definition. Userspace should populate the @version field to
> - * inform the driver about the version it intends to use. The driver will parse
> - * and handle the @data buffer according to the data layout specific to the
> - * indicated revision and return an error if the desired revision is not
> - * supported.
> - *
> - * For each ISP block that userspace wants to configure, a block-specific
> - * structure is appended to the @data buffer, one after the other without gaps
> - * in between nor overlaps. Userspace shall populate the @total_size field with
> - * the effective size, in bytes, of the @data buffer.
> + * This is the driver-specific implementation of :c:type:`v4l2_params_buffer`.
> + *
> + * Currently only C3_ISP_PARAM_BUFFER_V0 is supported.
>    *
>    * The expected memory layout of the parameters buffer is::
>    *
> @@ -561,4 +537,10 @@ struct c3_isp_params_cfg {
>   	__u8 data[C3_ISP_PARAMS_MAX_SIZE];
>   };
>   
> +#ifdef __KERNEL__
> +/* Make sure the header is type-convertible to the generic v4l2 params one */
> +static_assert((sizeof(struct c3_isp_params_cfg) - C3_ISP_PARAMS_MAX_SIZE) ==
> +	      sizeof(struct v4l2_params_buffer));
> +#endif /* __KERNEL__ */
> +
>   #endif
>