--- /dev/null
+.. -*- coding: utf-8; mode: rst -*-
+
+.. _v4l2-meta-fmt-params:
+.. _v4l2-meta-fmt-stat-3a:
+
+******************************************************************
+V4L2_META_FMT_IPU3_PARAMS ('ip3p'), V4L2_META_FMT_IPU3_3A ('ip3s')
+******************************************************************
+
+.. c:type:: ipu3_uapi_stats_3a
+
+3A statistics
+=============
+
+For IPU3 ImgU, the 3A statistics accelerators collect different statistics over
+an input bayer frame. Those statistics, defined in data struct :c:type:`ipu3_uapi_stats_3a`,
+are obtained from "ipu3-imgu 3a stat" metadata capture video node, which are then
+passed to user space for statistics analysis using :c:type:`v4l2_meta_format` interface.
+
+The statistics collected are AWB (Auto-white balance) RGBS (Red, Green, Blue and
+Saturation measure) cells, AWB filter response, AF (Auto-focus) filter response,
+and AE (Auto-exposure) histogram.
+
+struct :c:type:`ipu3_uapi_4a_config` saves configurable parameters for all above.
+
+.. code-block:: c
+
+ struct ipu3_uapi_stats_3a {
+ struct ipu3_uapi_awb_raw_buffer awb_raw_buffer;
+ struct ipu3_uapi_ae_raw_buffer_aligned ae_raw_buffer[IPU3_UAPI_MAX_STRIPES];
+ struct ipu3_uapi_af_raw_buffer af_raw_buffer;
+ struct ipu3_uapi_awb_fr_raw_buffer awb_fr_raw_buffer;
+ struct ipu3_uapi_4a_config stats_4a_config;
+ __u32 ae_join_buffers;
+ __u8 padding[28];
+ struct ipu3_uapi_stats_3a_bubble_info_per_stripe stats_3a_bubble_per_stripe;
+ struct ipu3_uapi_ff_status stats_3a_status;
+ };
+
+.. c:type:: ipu3_uapi_params
+
+Pipeline parameters
+===================
+
+IPU3 pipeline has a number of image processing stages, each of which takes a
+set of parameters as input. The major stages of pipelines are shown here:
+
+Raw pixels -> Bayer Downscaling -> Optical Black Correction ->
+
+Linearization -> Lens Shading Correction -> White Balance / Exposure /
+
+Focus Apply -> Bayer Noise Reduction -> ANR -> Demosaicing -> Color
+
+Correction Matrix -> Gamma correction -> Color Space Conversion ->
+
+Chroma Down Scaling -> Chromatic Noise Reduction -> Total Color
+
+Correction -> XNR3 -> TNR -> DDR
+
+The table below presents a description of the above algorithms.
+
+======================== =======================================================
+Name Description
+======================== =======================================================
+Optical Black Correction Optical Black Correction block subtracts a pre-defined
+ value from the respective pixel values to obtain better
+ image quality.
+ Defined in :c:type:`ipu3_uapi_obgrid_param`.
+Linearization This algo block uses linearization parameters to
+ address non-linearity sensor effects. The Lookup table
+ table is defined in
+ :c:type:`ipu3_uapi_isp_lin_vmem_params`.
+SHD Lens shading correction is used to correct spatial
+ non-uniformity of the pixel response due to optical
+ lens shading. This is done by applying a different gain
+ for each pixel. The gain, black level etc are
+ configured in :c:type:`ipu3_uapi_shd_config_static`.
+BNR Bayer noise reduction block removes image noise by
+ applying a bilateral filter.
+ See :c:type:`ipu3_uapi_bnr_static_config` for details.
+ANR Advanced Noise Reduction is a block based algorithm
+ that performs noise reduction in the Bayer domain. The
+ convolution matrix etc can be found in
+ :c:type:`ipu3_uapi_anr_config`.
+Demosaicing Demosaicing converts raw sensor data in Bayer format
+ into RGB (Red, Green, Blue) presentation. Then add
+ outputs of estimation of Y channel for following stream
+ processing by Firmware. The struct is defined as
+ :c:type:`ipu3_uapi_dm_config`. (TODO)
+Color Correction Color Correction algo transforms sensor specific color
+ space to the standard "sRGB" color space. This is done
+ by applying 3x3 matrix defined in
+ :c:type:`ipu3_uapi_ccm_mat_config`.
+Gamma correction Gamma correction :c:type:`ipu3_uapi_gamma_config` is a
+ basic non-linear tone mapping correction that is
+ applied per pixel for each pixel component.
+CSC Color space conversion transforms each pixel from the
+ RGB primary presentation to YUV (Y: brightness,
+ UV: Luminance) presentation. This is done by applying
+ a 3x3 matrix defined in
+ :c:type:`ipu3_uapi_csc_mat_config`
+CDS Chroma down sampling
+ After the CSC is performed, the Chroma Down Sampling
+ is applied for a UV plane down sampling by a factor
+ of 2 in each direction for YUV 4:2:0 using a 4x2
+ configurable filter :c:type:`ipu3_uapi_cds_params`.
+CHNR Chroma noise reduction
+ This block processes only the chrominance pixels and
+ performs noise reduction by cleaning the high
+ frequency noise.
+ See struct :c:type:`ipu3_uapi_yuvp1_chnr_config`.
+TCC Total color correction as defined in struct
+ :c:type:`ipu3_uapi_yuvp2_tcc_static_config`.
+XNR3 eXtreme Noise Reduction V3 is the third revision of
+ noise reduction algorithm used to improve image
+ quality. This removes the low frequency noise in the
+ captured image. Two related structs are being defined,
+ :c:type:`ipu3_uapi_isp_xnr3_params` for ISP data memory
+ and :c:type:`ipu3_uapi_isp_xnr3_vmem_params` for vector
+ memory.
+TNR Temporal Noise Reduction block compares successive
+ frames in time to remove anomalies / noise in pixel
+ values. :c:type:`ipu3_uapi_isp_tnr3_vmem_params` and
+ :c:type:`ipu3_uapi_isp_tnr3_params` are defined for ISP
+ vector and data memory respectively.
+======================== =======================================================
+
+A few stages of the pipeline will be executed by firmware running on the ISP
+processor, while many others will use a set of fixed hardware blocks also
+called accelerator cluster (ACC) to crunch pixel data and produce statistics.
+
+ACC parameters of individual algorithms, as defined by
+:c:type:`ipu3_uapi_acc_param`, can be chosen to be applied by the user
+space through struct :c:type:`ipu3_uapi_flags` embedded in
+:c:type:`ipu3_uapi_params` structure. For parameters that are configured as
+not enabled by the user space, the corresponding structs are ignored by the
+driver, in which case the existing configuration of the algorithm will be
+preserved.
+
+Both 3A statistics and pipeline parameters described here are closely tied to
+the underlying camera sub-system (CSS) APIs. They are usually consumed and
+produced by dedicated user space libraries that comprise the important tuning
+tools, thus freeing the developers from being bothered with the low level
+hardware and algorithm details.
+
+It should be noted that IPU3 DMA operations require the addresses of all data
+structures (that includes both input and output) to be aligned on 32 byte
+boundaries.
+
+The meta data :c:type:`ipu3_uapi_params` will be sent to "ipu3-imgu parameters"
+video node in ``V4L2_BUF_TYPE_META_CAPTURE`` format.
+
+.. code-block:: c
+
+ struct ipu3_uapi_params {
+ /* Flags which of the settings below are to be applied */
+ struct ipu3_uapi_flags use;
+
+ /* Accelerator cluster parameters */
+ struct ipu3_uapi_acc_param acc_param;
+
+ /* ISP vector address space parameters */
+ struct ipu3_uapi_isp_lin_vmem_params lin_vmem_params;
+ struct ipu3_uapi_isp_tnr3_vmem_params tnr3_vmem_params;
+ struct ipu3_uapi_isp_xnr3_vmem_params xnr3_vmem_params;
+
+ /* ISP data memory (DMEM) parameters */
+ struct ipu3_uapi_isp_tnr3_params tnr3_dmem_params;
+ struct ipu3_uapi_isp_xnr3_params xnr3_dmem_params;
+
+ /* Optical black level compensation */
+ struct ipu3_uapi_obgrid_param obgrid_param;
+ };
+
+Intel IPU3 ImgU uAPI data types
+===============================
+
+.. kernel-doc:: include/uapi/linux/intel-ipu3.h
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