[libcamera-devel] [PATCH v8 5/5] ipa: ipu3: Replace ipa::ipu3::algorithms::Ipu3AwbCell

[Laurent Pinchart]

Hi Jean-Michel,

Thank you for the patch.

On Tue, Sep 14, 2021 at 06:37:09PM +0200, Jean-Michel Hautbois wrote:
> The intel-ipu3.h public interface from the kernel does not define how to
> parse the statistics for a cell. This had to be identified by a process
> of reverse engineering, and later identifying the structures from [0]
> leading to our custom definition of struct Ipu3AwbCell.
> 
> [0]
> https://chromium.googlesource.com/chromiumos/platform/arc-camera/+/refs/heads/master/hal/intel/include/ia_imaging/awb_public.h
> 
> To improve the kernel interface, a proposal has been made to the
> linux-kernel [1] to incorporate the memory layout for each cell into the
> intel-ipu3 header directly.
> 
> [1]
> https://lore.kernel.org/linux-media/20210831185140.77400-1-jeanmichel.hautbois@ideasonboard.com/
> 
> Update our local copy of the intel-ipu3.h to match the proposal and
> change the AGC and AWB algorithms to reference that structure directly,
> allowing us to remove the deprecated custom Ipu3AwbCell definition.
> 
> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
>  include/linux/intel-ipu3.h      | 28 ++++++++++++++++++++++++++--
>  src/ipa/ipu3/algorithms/agc.cpp | 11 +++++------
>  src/ipa/ipu3/algorithms/awb.cpp | 13 ++++++-------
>  src/ipa/ipu3/algorithms/awb.h   | 10 ----------
>  4 files changed, 37 insertions(+), 25 deletions(-)
> 
> diff --git a/include/linux/intel-ipu3.h b/include/linux/intel-ipu3.h
> index ee0e6d0e..a9de8c11 100644
> --- a/include/linux/intel-ipu3.h
> +++ b/include/linux/intel-ipu3.h
> @@ -59,6 +59,29 @@ struct ipu3_uapi_grid_config {
>  	__u16 y_end;
>  } __attribute__((packed));
>  
> +/**
> + * struct ipu3_uapi_awb_set_item - Memory layout for each cell in AWB
> + *
> + * @Gr_avg:	Green average for red lines in the cell.
> + * @R_avg:	Red average in the cell.
> + * @B_avg:	Blue average in the cell.
> + * @Gb_avg:	Green average for blue lines in the cell.
> + * @sat_ratio:  Saturation ratio in the cell.
> + * @padding0:   Unused byte for padding.
> + * @padding1:   Unused byte for padding.
> + * @padding2:   Unused byte for padding.
> + */
> +struct ipu3_uapi_awb_set_item {
> +	unsigned char Gr_avg;
> +	unsigned char R_avg;
> +	unsigned char B_avg;
> +	unsigned char Gb_avg;
> +	unsigned char sat_ratio;
> +	unsigned char padding0;
> +	unsigned char padding1;
> +	unsigned char padding2;
> +} __attribute__((packed));
> +
>  /*
>   * The grid based data is divided into "slices" called set, each slice of setX
>   * refers to ipu3_uapi_grid_config width * height_per_slice.
> @@ -72,7 +95,8 @@ struct ipu3_uapi_grid_config {
>  	 IPU3_UAPI_AWB_MD_ITEM_SIZE)
>  #define IPU3_UAPI_AWB_MAX_BUFFER_SIZE \
>  	(IPU3_UAPI_AWB_MAX_SETS * \
> -	 (IPU3_UAPI_AWB_SET_SIZE + IPU3_UAPI_AWB_SPARE_FOR_BUBBLES))
> +	 (IPU3_UAPI_AWB_SET_SIZE + IPU3_UAPI_AWB_SPARE_FOR_BUBBLES)) / \
> +	 sizeof(ipu3_uapi_awb_set_item)
>  
>  
>  /**
> @@ -82,7 +106,7 @@ struct ipu3_uapi_grid_config {
>   *		the average values for each color channel.
>   */
>  struct ipu3_uapi_awb_raw_buffer {
> -	__u8 meta_data[IPU3_UAPI_AWB_MAX_BUFFER_SIZE]
> +	struct ipu3_uapi_awb_set_item meta_data[IPU3_UAPI_AWB_MAX_BUFFER_SIZE]
>  		__attribute__((aligned(32)));
>  } __attribute__((packed));
>  
> diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
> index 52e8015e..a3e910b7 100644
> --- a/src/ipa/ipu3/algorithms/agc.cpp
> +++ b/src/ipa/ipu3/algorithms/agc.cpp
> @@ -72,14 +72,13 @@ void Agc::processBrightness(const ipu3_uapi_stats_3a *stats,
>  
>  	for (unsigned int cellY = 0; cellY < grid.height; cellY++) {
>  		for (unsigned int cellX = 0; cellX < grid.width; cellX++) {
> -			uint32_t cellPosition = (cellY * grid.width + cellX)
> -					      * sizeof(Ipu3AwbCell);
> +			uint32_t cellPosition = cellY * grid.width + cellX;
>  
>  			/* Cast the initial IPU3 structure to simplify the reading */
> -			Ipu3AwbCell *currentCell = reinterpret_cast<Ipu3AwbCell *>(const_cast<uint8_t *>(&stats->awb_raw_buffer.meta_data[cellPosition]));
> -			if (currentCell->satRatio == 0) {
> -				uint8_t Gr = currentCell->greenRedAvg;
> -				uint8_t Gb = currentCell->greenBlueAvg;
> +			const ipu3_uapi_awb_set_item *currentCell = &stats->awb_raw_buffer.meta_data[cellPosition];

Naming the variable "cell" will give you shorter lines without any
decrease in readability (I think). Same below.

> +			if (currentCell->sat_ratio == 0) {
> +				uint8_t Gr = currentCell->Gr_avg;
> +				uint8_t Gb = currentCell->Gb_avg;
>  				hist[(Gr + Gb) / 2]++;
>  			}
>  		}
> diff --git a/src/ipa/ipu3/algorithms/awb.cpp b/src/ipa/ipu3/algorithms/awb.cpp
> index b96a6ebf..6d8438af 100644
> --- a/src/ipa/ipu3/algorithms/awb.cpp
> +++ b/src/ipa/ipu3/algorithms/awb.cpp
> @@ -229,22 +229,21 @@ void Awb::generateAwbStats(const ipu3_uapi_stats_3a *stats,
>  	 */
>  	for (unsigned int cellY = 0; cellY < kAwbStatsSizeY * cellsPerZoneY; cellY++) {
>  		for (unsigned int cellX = 0; cellX < kAwbStatsSizeX * cellsPerZoneX; cellX++) {
> -			uint32_t cellPosition = (cellY * grid.width + cellX)
> -					      * sizeof(Ipu3AwbCell);
> +			uint32_t cellPosition = cellY * grid.width + cellX;
>  			uint32_t zoneX = cellX / cellsPerZoneX;
>  			uint32_t zoneY = cellY / cellsPerZoneY;
>  
>  			uint32_t awbZonePosition = zoneY * kAwbStatsSizeX + zoneX;
>  
>  			/* Cast the initial IPU3 structure to simplify the reading */
> -			Ipu3AwbCell *currentCell = reinterpret_cast<Ipu3AwbCell *>(const_cast<uint8_t *>(&stats->awb_raw_buffer.meta_data[cellPosition]));
> -			if (currentCell->satRatio == 0) {
> +			const ipu3_uapi_awb_set_item *currentCell = &stats->awb_raw_buffer.meta_data[cellPosition];
> +			if (currentCell->sat_ratio == 0) {
>  				/* The cell is not saturated, use the current cell */
>  				awbStats_[awbZonePosition].counted++;
> -				uint32_t greenValue = currentCell->greenRedAvg + currentCell->greenBlueAvg;
> +				uint32_t greenValue = currentCell->Gr_avg + currentCell->Gb_avg;
>  				awbStats_[awbZonePosition].sum.green += greenValue / 2;
> -				awbStats_[awbZonePosition].sum.red += currentCell->redAvg;
> -				awbStats_[awbZonePosition].sum.blue += currentCell->blueAvg;
> +				awbStats_[awbZonePosition].sum.red += currentCell->R_avg;
> +				awbStats_[awbZonePosition].sum.blue += currentCell->B_avg;
>  			}
>  		}
>  	}
> diff --git a/src/ipa/ipu3/algorithms/awb.h b/src/ipa/ipu3/algorithms/awb.h
> index 3385ebe7..17905ae8 100644
> --- a/src/ipa/ipu3/algorithms/awb.h
> +++ b/src/ipa/ipu3/algorithms/awb.h
> @@ -23,16 +23,6 @@ namespace ipa::ipu3::algorithms {
>  static constexpr uint32_t kAwbStatsSizeX = 16;
>  static constexpr uint32_t kAwbStatsSizeY = 12;
>  
> -/* \todo Move the cell layout into intel-ipu3.h kernel header */
> -struct Ipu3AwbCell {
> -	unsigned char greenRedAvg;
> -	unsigned char redAvg;
> -	unsigned char blueAvg;
> -	unsigned char greenBlueAvg;
> -	unsigned char satRatio;
> -	unsigned char padding[3];
> -} __attribute__((packed));
> -
>  struct Accumulator {
>  	unsigned int counted;
>  	struct {

-- 
Regards,

Laurent Pinchart