[libcamera-devel] [PATCH v3 4/5] ipa: ipu3: af: Use Span for y_table_item_t

[Jean-Michel Hautbois]

Hi Kieran,

Thanks for the patch !

On 25/03/2022 10:25, Kieran Bingham wrote:
> Convert the y_table_item_t to a Span and use that for iteration when
> estimating variance of the table.
> 
> Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Reviewed-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>

> 
> ---
> v3:
>   - Remove parentheses and casting in afEstimateVariance
> 
>   src/ipa/ipu3/algorithms/af.cpp | 34 +++++++++++++++++-----------------
>   src/ipa/ipu3/algorithms/af.h   |  4 ++--
>   2 files changed, 19 insertions(+), 19 deletions(-)
> 
> diff --git a/src/ipa/ipu3/algorithms/af.cpp b/src/ipa/ipu3/algorithms/af.cpp
> index 6893a15fdc07..c0f2d34368cb 100644
> --- a/src/ipa/ipu3/algorithms/af.cpp
> +++ b/src/ipa/ipu3/algorithms/af.cpp
> @@ -335,29 +335,29 @@ void Af::afIgnoreFrameReset()
>    *
>    * \return The variance of the values in the data set \a y_item selected by \a isY1
>    */
> -double Af::afEstimateVariance(const y_table_item_t *y_item, uint32_t len,
> -			      bool isY1)
> +double Af::afEstimateVariance(Span<const y_table_item_t> y_items, bool isY1)
>   {
> -	uint32_t z = 0;
>   	uint32_t total = 0;
>   	double mean;
>   	double var_sum = 0;
>   
> -	for (z = 0; z < len; z++) {
> +	for (auto y : y_items) {
>   		if (isY1)
> -			total += y_item[z].y1_avg;
> +			total += y.y1_avg;
>   		else
> -			total += y_item[z].y2_avg;
> +			total += y.y2_avg;
>   	}
> -	mean = total / len;
> -	for (z = 0; z < len; z++) {
> +
> +	mean = total / y_items.size();
> +
> +	for (auto y : y_items) {
>   		if (isY1)
> -			var_sum += pow((y_item[z].y1_avg - mean), 2);
> +			var_sum += pow(y.y1_avg - mean, 2);
>   		else
> -			var_sum += pow((y_item[z].y2_avg - mean), 2);
> +			var_sum += pow(y.y2_avg - mean, 2);
>   	}
>   
> -	return var_sum / static_cast<double>(len);
> +	return var_sum / y_items.size();
>   }
>   
>   /**
> @@ -405,21 +405,21 @@ bool Af::afIsOutOfFocus(IPAContext context)
>    */
>   void Af::process(IPAContext &context, const ipu3_uapi_stats_3a *stats)
>   {
> -	const y_table_item_t *y_item = reinterpret_cast<const y_table_item_t *>(&stats->af_raw_buffer.y_table);
> -	uint32_t afRawBufferLen;
> -
>   	/* Evaluate the AF buffer length */
> -	afRawBufferLen = context.configuration.af.afGrid.width *
> -			 context.configuration.af.afGrid.height;
> +	uint32_t afRawBufferLen = context.configuration.af.afGrid.width *
> +				  context.configuration.af.afGrid.height;
>   
>   	ASSERT(afRawBufferLen < IPU3_UAPI_AF_Y_TABLE_MAX_SIZE);
>   
> +	Span<const y_table_item_t> y_items(reinterpret_cast<const y_table_item_t *>(&stats->af_raw_buffer.y_table),
> +					   afRawBufferLen);
> +
>   	/*
>   	 * Calculate the mean and the variance of AF statistics for a given grid.
>   	 * For coarse: y1 are used.
>   	 * For fine: y2 results are used.
>   	 */
> -	currentVariance_ = afEstimateVariance(y_item, afRawBufferLen, !coarseCompleted_);
> +	currentVariance_ = afEstimateVariance(y_items, !coarseCompleted_);
>   
>   	if (!context.frameContext.af.stable) {
>   		afCoarseScan(context);
> diff --git a/src/ipa/ipu3/algorithms/af.h b/src/ipa/ipu3/algorithms/af.h
> index 3b5758e868ea..b85cf94163ff 100644
> --- a/src/ipa/ipu3/algorithms/af.h
> +++ b/src/ipa/ipu3/algorithms/af.h
> @@ -41,8 +41,8 @@ private:
>   	void afReset(IPAContext &context);
>   	bool afNeedIgnoreFrame();
>   	void afIgnoreFrameReset();
> -	double afEstimateVariance(const y_table_item_t *y_item, uint32_t len,
> -				  bool isY1);
> +	double afEstimateVariance(Span<const y_table_item_t> y_items, bool isY1);
> +
>   	bool afIsOutOfFocus(IPAContext context);
>   
>   	/* VCM step configuration. It is the current setting of the VCM step. */