Re: [PATCH v1 03/11] media: v4l2-isp: Add helper function to compute extended stats size

Jacopo Mondi
2026-04-17T07:15:58Z

Hi Antoine

On Mon, Apr 13, 2026 at 06:03:23PM +0200, Antoine Bouyer wrote:
> v4l2-isp framework only supports extended buffer for generic ISP
> configuration. This patch adds simple helper function to compute the
> extended statistics buffer size, exactly the same as for extended
> parameters, except that it uses the `v4l2_isp_stats_block_header`
> structure definition to prevent conflict with the
> `v4l2_isp_params_block_header` one.
>
> Signed-off-by: Antoine Bouyer <antoine.bouyer@nxp.com>
> ---
> include/media/v4l2-isp.h | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/include/media/v4l2-isp.h b/include/media/v4l2-isp.h
> index f3a6d0edcb24..9a93a534e7b0 100644
> --- a/include/media/v4l2-isp.h
> +++ b/include/media/v4l2-isp.h
> @@ -27,6 +27,19 @@ struct vb2_buffer;
> #define v4l2_isp_params_buffer_size(max_params_size) \
> (offsetof(struct v4l2_isp_params_buffer, data) + (max_params_size))
>
> +/**
> + * v4l2_isp_stats_buffer_size - Calculate size of v4l2_isp_stats_buffer
> + * @max_stats_size: The total size of the ISP statistic blocks
> + *
> + * Users of the v4l2 extensible statistics buffers will have differing sized data
> + * arrays depending on their specific ISP blocks. Drivers and userspace will need
> + * to be able to calculate the appropriate size of the struct to accommodate all
> + * ISP statistics blocks provided by the platform.
> + * This macro provides a convenient tool for the calculation.
> + */
> +#define v4l2_isp_stats_buffer_size(max_stats_size) \
> + (offsetof(struct v4l2_isp_stats_buffer, data) + (max_stats_size))
> +

Should we do this or simply:

--- a/include/media/v4l2-isp.h
+++ b/include/media/v4l2-isp.h
@@ -15,17 +15,21 @@ 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
+ * v4l2_isp_buffer_size - Calculate size of v4l2_isp_buffer
+ * @max_size: The total size of the ISP configuration or statistics blocks
+ *
+ * Users of v4l2-isp will have differing sized data arrays for parameters and
+ * statistics, depending on their specific blocks. Drivers need to be able to
+ * calculate the appropriate size of the buffer to accommodate all ISP blocks
+ * supported by the platform. This macro provides a convenient tool for the
+ * calculation.
+ *
+ * The intended users of this function are drivers initializing the size
+ * of their metadata (parameters and statistics) buffers.
*
- * 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))
+#define v4l2_isp_buffer_size(max_size) \
+ (offsetof(struct v4l2_isp_buffer, data) + (max_size))

(I wrote this before noticing your patch :)

> /**
> * v4l2_isp_params_validate_buffer_size - Validate a V4L2 ISP buffer sizes
> * @dev: the driver's device pointer
> --
> 2.51.0
>