ipa: ipu3: Isolate ipa_context documentation

The IPU3 IPA core is growing with additional documentation. The
ipa_context documentation is stored here, but it pushes the IPU3
documentation and implementation further from the head of the file.

Furthermore, the ipa_context documentation is outside of the ipa::ipu3
namespace and isn't identified correctly by Doxygen.

Move the ipa_context to its own compilation object even though there
isn't any code, but to maintain consistency with our documentation
model.

Correctly re-introduce the documentation into the libcamera::ipa::ipu3
namespace during the move.

Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>

1 files changed, 136 insertions, 0 deletions

diff --git a/src/ipa/ipu3/ipa_context.cpp b/src/ipa/ipu3/ipa_context.cpp
new file mode 100644
index 00000000..94a5f7f6
--- /dev/null
+++ b/src/ipa/ipu3/ipa_context.cpp
@@ -0,0 +1,136 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Google Inc.
+ *
+ * ipa_context.cpp - IPU3 IPA Context
+ */
+
+#include "ipa_context.h"
+
+/**
+ * \file ipa_context.h
+ * \brief Context and state information shared between the algorithms
+ */
+
+namespace libcamera::ipa::ipu3 {
+
+/**
+ * \struct IPASessionConfiguration
+ * \brief Session configuration for the IPA module
+ *
+ * The session configuration contains all IPA configuration parameters that
+ * remain constant during the capture session, from IPA module start to stop.
+ * It is typically set during the configure() operation of the IPA module, but
+ * may also be updated in the start() operation.
+ */
+
+/**
+ * \struct IPAFrameContext
+ * \brief Per-frame context for algorithms
+ *
+ * The frame context stores data specific to a single frame processed by the
+ * IPA. Each frame processed by the IPA has a context associated with it,
+ * accessible through the IPAContext structure.
+ *
+ * \todo Detail how to access contexts for a particular frame
+ *
+ * Each of the fields in the frame context belongs to either a specific
+ * algorithm, or to the top-level IPA module. A field may be read by any
+ * algorithm, but should only be written by its owner.
+ */
+
+/**
+ * \struct IPAContext
+ * \brief Global IPA context data shared between all algorithms
+ *
+ * \var IPAContext::configuration
+ * \brief The IPA session configuration, immutable during the session
+ *
+ * \var IPAContext::frameContext
+ * \brief The frame context for the frame being processed
+ *
+ * \todo While the frame context is supposed to be per-frame, this
+ * single frame context stores data related to both the current frame
+ * and the previous frames, with fields being updated as the algorithms
+ * are run. This needs to be turned into real per-frame data storage.
+ */
+
+/**
+ * \struct IPASessionConfiguration::grid
+ * \brief Grid configuration of the IPA
+ *
+ * \var IPASessionConfiguration::grid::bdsGrid
+ * \brief Bayer Down Scaler grid plane config used by the kernel
+ *
+ * \var IPASessionConfiguration::grid::bdsOutputSize
+ * \brief BDS output size configured by the pipeline handler
+ *
+ * \var IPASessionConfiguration::grid::stride
+ * \brief Number of cells on one line including the ImgU padding
+ */
+
+/**
+ * \struct IPASessionConfiguration::agc
+ * \brief AGC parameters configuration of the IPA
+ *
+ * \var IPASessionConfiguration::agc::minShutterSpeed
+ * \brief Minimum shutter speed supported with the configured sensor
+ *
+ * \var IPASessionConfiguration::grid::maxShutterSpeed
+ * \brief Maximum shutter speed supported with the configured sensor
+ *
+ * \var IPASessionConfiguration::grid::minAnalogueGain
+ * \brief Minimum analogue gain supported with the configured sensor
+ *
+ * \var IPASessionConfiguration::grid::maxAnalogueGain
+ * \brief Maximum analogue gain supported with the configured sensor
+ */
+
+/**
+ * \struct IPAFrameContext::agc
+ * \brief Context for the Automatic Gain Control algorithm
+ *
+ * The exposure and gain determined are expected to be applied to the sensor
+ * at the earliest opportunity.
+ *
+ * \var IPAFrameContext::agc::exposure
+ * \brief Exposure time expressed as a number of lines
+ *
+ * \var IPAFrameContext::agc::gain
+ * \brief Analogue gain multiplier
+ *
+ * The gain should be adapted to the sensor specific gain code before applying.
+ */
+
+/**
+ * \struct IPAFrameContext::awb
+ * \brief Context for the Automatic White Balance algorithm
+ *
+ * \struct IPAFrameContext::awb::gains
+ * \brief White balance gains
+ *
+ * \var IPAFrameContext::awb::gains::red
+ * \brief White balance gain for R channel
+ *
+ * \var IPAFrameContext::awb::gains::green
+ * \brief White balance gain for G channel
+ *
+ * \var IPAFrameContext::awb::gains::blue
+ * \brief White balance gain for B channel
+ */
+
+/**
+ * \struct IPAFrameContext::toneMapping
+ * \brief Context for ToneMapping and Gamma control
+ *
+ * \var IPAFrameContext::toneMapping::gamma
+ * \brief Gamma value for the LUT
+ *
+ * \var IPAFrameContext::toneMapping::gammaCorrection
+ * \brief Per-pixel tone mapping implemented as a LUT
+ *
+ * The LUT structure is defined by the IPU3 kernel interface. See
+ * <linux/intel-ipu3.h> struct ipu3_uapi_gamma_corr_lut for further details.
+ */
+
+} /* namespace libcamera::ipa::ipu3 */