[libcamera-devel,RFC,04/12] ipa: ipu3: Move the Frame Context queue to libipa

16716 diff mbox series

From: Umang Jain <umang.jain@ideasonboard.com>

Provide a direct FCQueue abstraction to facilitate creating a queue of
Frame Context structures.

The IPAFrameContext is moved back to the ipu3/ipa_context.h and a queue
added to the IPU3, but the Algorithms are not yet moved from the single
FrameContext exposed by the IPA context to use the correct one from the
queue until the Algorithm interfaces are fully updated.

Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
---
 src/ipa/ipu3/ipa_context.cpp | 17 -------
 src/ipa/ipu3/ipa_context.h   | 15 ++----
 src/ipa/ipu3/ipu3.cpp        | 13 +++--
 src/ipa/libipa/fc_queue.cpp  | 96 ++++++++++++++++++++++++++++++++++++
 src/ipa/libipa/fc_queue.h    | 93 ++++++++++++++++++++++++++++++++++
 src/ipa/libipa/meson.build   |  2 +
 6 files changed, 204 insertions(+), 32 deletions(-)
 create mode 100644 src/ipa/libipa/fc_queue.cpp
 create mode 100644 src/ipa/libipa/fc_queue.h

Hi Kieran,

On 7/21/22 17:43, Kieran Bingham wrote:
> From: Umang Jain <umang.jain@ideasonboard.com>
>
> Provide a direct FCQueue abstraction to facilitate creating a queue of
> Frame Context structures.


Ah we are back again to have FCQueue separately (in class files) :-)

>
> The IPAFrameContext is moved back to the ipu3/ipa_context.h and a queue


You can just say that the constructors for IPAFrameContext are dropped.


> added to the IPU3, but the Algorithms are not yet moved from the single

nit: s/IPU3/IPAIPU3/

Furthermore, a queue is already present in the form of:

         std::array<IPAFrameContext, kMaxFrameContexts> frameContexts;

It is just that the queue is transformed to FCQueue. Since this is a 
RFC, I won't dwell much on the commit message, it can get accurately 
described in future interations.

> FrameContext exposed by the IPA context to use the correct one from the
> queue until the Algorithm interfaces are fully updated.
>
> Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> ---
>   src/ipa/ipu3/ipa_context.cpp | 17 -------
>   src/ipa/ipu3/ipa_context.h   | 15 ++----
>   src/ipa/ipu3/ipu3.cpp        | 13 +++--
>   src/ipa/libipa/fc_queue.cpp  | 96 ++++++++++++++++++++++++++++++++++++
>   src/ipa/libipa/fc_queue.h    | 93 ++++++++++++++++++++++++++++++++++
>   src/ipa/libipa/meson.build   |  2 +
>   6 files changed, 204 insertions(+), 32 deletions(-)
>   create mode 100644 src/ipa/libipa/fc_queue.cpp
>   create mode 100644 src/ipa/libipa/fc_queue.h
>
> diff --git a/src/ipa/ipu3/ipa_context.cpp b/src/ipa/ipu3/ipa_context.cpp
> index 13cdb835ef7f..dd139cb4c868 100644
> --- a/src/ipa/ipu3/ipa_context.cpp
> +++ b/src/ipa/ipu3/ipa_context.cpp
> @@ -180,27 +180,10 @@ namespace libcamera::ipa::ipu3 {
>    * <linux/intel-ipu3.h> struct ipu3_uapi_gamma_corr_lut for further details.
>    */
>   
> -/**
> - * \brief Default constructor for IPAFrameContext
> - */
> -IPAFrameContext::IPAFrameContext() = default;
> -
> -/**
> - * \brief Construct a IPAFrameContext instance
> - */
> -IPAFrameContext::IPAFrameContext(uint32_t id, const ControlList &reqControls)
> -	: frame(id), frameControls(reqControls)
> -{
> -	sensor = {};
> -}
> -
>   /**
>    * \var IPAFrameContext::frame
>    * \brief The frame number
>    *
> - * \var IPAFrameContext::frameControls
> - * \brief Controls sent in by the application while queuing the request
> - *
>    * \var IPAFrameContext::sensor
>    * \brief Effective sensor values that were applied for the frame
>    *
> diff --git a/src/ipa/ipu3/ipa_context.h b/src/ipa/ipu3/ipa_context.h
> index 42e11141d3a1..193fc44a821a 100644
> --- a/src/ipa/ipu3/ipa_context.h
> +++ b/src/ipa/ipu3/ipa_context.h
> @@ -8,8 +8,6 @@
>   
>   #pragma once
>   
> -#include <array>
> -
>   #include <linux/intel-ipu3.h>
>   
>   #include <libcamera/base/utils.h>
> @@ -17,13 +15,12 @@
>   #include <libcamera/controls.h>
>   #include <libcamera/geometry.h>
>   
> +#include <libipa/fc_queue.h>
> +
>   namespace libcamera {
>   
>   namespace ipa::ipu3 {
>   
> -/* Maximum number of frame contexts to be held */
> -static constexpr uint32_t kMaxFrameContexts = 16;
> -
>   struct IPASessionConfiguration {
>   	struct {
>   		ipu3_uapi_grid_config bdsGrid;
> @@ -77,23 +74,19 @@ struct IPAActiveState {
>   };
>   
>   struct IPAFrameContext {
> -	IPAFrameContext();
> -	IPAFrameContext(uint32_t id, const ControlList &reqControls);
> +	uint32_t frame;
>   
>   	struct {
>   		uint32_t exposure;
>   		double gain;
>   	} sensor;
> -
> -	uint32_t frame;
> -	ControlList frameControls;


Okay, we dropped the ControlList here, because every algo will get the 
ControlList in the new interface

>   };
>   
>   struct IPAContext {
>   	IPASessionConfiguration configuration;
>   	IPAActiveState activeState;
>   
> -	std::array<IPAFrameContext, kMaxFrameContexts> frameContexts;
> +	FCQueue<IPAFrameContext> frameContexts;
>   };
>   
>   } /* namespace ipa::ipu3 */
> diff --git a/src/ipa/ipu3/ipu3.cpp b/src/ipa/ipu3/ipu3.cpp
> index 2f6bb672f7bb..55e82cd404f4 100644
> --- a/src/ipa/ipu3/ipu3.cpp
> +++ b/src/ipa/ipu3/ipu3.cpp
> @@ -38,6 +38,8 @@
>   #include "algorithms/tone_mapping.h"
>   #include "libipa/camera_sensor_helper.h"
>   
> +#include "ipa_context.h"
> +
>   /* Minimum grid width, expressed as a number of cells */
>   static constexpr uint32_t kMinGridWidth = 16;
>   /* Maximum grid width, expressed as a number of cells */
> @@ -456,8 +458,7 @@ int IPAIPU3::configure(const IPAConfigInfo &configInfo,
>   
>   	/* Clean IPAActiveState at each reconfiguration. */
>   	context_.activeState = {};
> -	IPAFrameContext initFrameContext;
> -	context_.frameContexts.fill(initFrameContext);
> +	context_.frameContexts.clear();
context_.frameContexts.clear();

Should also be done in IPAIPU3::stop().

>   
>   	if (!validateSensorControls()) {
>   		LOG(IPAIPU3, Error) << "Sensor control validation failed.";
> @@ -569,7 +570,7 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
>   	const ipu3_uapi_stats_3a *stats =
>   		reinterpret_cast<ipu3_uapi_stats_3a *>(mem.data());
>   
> -	IPAFrameContext &frameContext = context_.frameContexts[frame % kMaxFrameContexts];
> +	IPAFrameContext &frameContext = context_.frameContexts.get(frame);
>   
>   	if (frameContext.frame != frame)
>   		LOG(IPAIPU3, Warning) << "Frame " << frame << " does not match its frame context";
> @@ -618,7 +619,11 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
>   void IPAIPU3::queueRequest(const uint32_t frame, const ControlList &controls)
>   {
>   	/* \todo Start processing for 'frame' based on 'controls'. */
> -	context_.frameContexts[frame % kMaxFrameContexts] = { frame, controls };
> +	IPAFrameContext &frameContext = context_.frameContexts.initialise(frame);
> +
> +	/* \todo Implement queueRequest to each algorithm. */
> +	(void)frameContext;
> +	(void)controls;
>   }
>   
>   /**
> diff --git a/src/ipa/libipa/fc_queue.cpp b/src/ipa/libipa/fc_queue.cpp
> new file mode 100644
> index 000000000000..ecb47f287350
> --- /dev/null
> +++ b/src/ipa/libipa/fc_queue.cpp
> @@ -0,0 +1,96 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2022, Google Inc.
> + *
> + * fc_queue.cpp - IPA Frame context queue
> + */
> +
> +#include "fc_queue.h"
> +
> +#include <libcamera/base/log.h>
> +
> +namespace libcamera {
> +
> +LOG_DEFINE_CATEGORY(FCQueue)
> +
> +namespace ipa {
> +
> +/**
> + * \file fc_queue.h
> + * \brief Queue to access per-frame Context
> + */
> +
> +/**
> + * \class FCQueue
> + * \brief A support class for queueing Frame Context instances through the IPA


s/queueing/queuing/

> + * \tparam FrameContext The IPA specific Frame Context type for this queue
> + *
> + * The Frame Context Queue provides a simple circular buffer implementation to
> + * store IPA specific context for each frame through its lifetime within the
> + * IPA.
> + *
> + * FrameContexts are expected to be referenced by a monotonically increasing
> + * sequence count referring to a Frame sequence.
> + *
> + * A FrameContext is initialised for a given frame when the corresponding
> + * Request is first queued into the IPA. From that point on the FrameContext can
> + * be obtained by the IPA and its algorithms by referencing it from the frame
> + * sequence number.
> + *
> + * A frame sequence number from the image source must correspond to the request
> + * sequence number for this implementation to be supported in an IPA. It is
> + * expected that the same sequence number will be used to reference the context
> + * of the Frame from the point of queueing the request, specifying controls for


s/queueing/queuing/

> + * a given frame, and processing of any ISP related controls and statistics for
> + * the same corresponding image.
> + *
> + * IPA specific FrameContexts should inherit from the IPAFrameContext to support
> + * the minimum required features for a FrameContext, including the frame number
> + * and error flags that relate to the frame.
> + *
> + * FrameContexts are overwritten when they are recycled and re-initialised by
> + * the first access made on them by either initialise(frame) or get(frame). If a
> + * FrameContext is first accessed through get(frame) before calling initialise()
> + * a PFCError is automatically raised on the FrameContext to be transferred to
> + * the Request when it completes.


I get the point here, but I feel the documentation on get()/PFCError 
etc. is a bit jerky.

Once we have some context setup for FCQ, goals, error situations etc. 
maybe it will fit into the flow.

> + */
> +
> +/**
> + * \fn FCQueue::clear()
> + * \brief Reinitialise all data on the queue
> + *
> + * Reset the queue and ensure all FrameContext slots are re-initialised.
> + */
> +
> +/**
> + * \fn FCQueue::initialise(uint32_t frame)
> + * \brief Initialize and return the Frame Context at slot specified by \a frame
> + * \param[in] frame The frame context sequence number
> + *
> + * The first call to obtain a FrameContext from the FCQueue should be handled
> + * through this call. The FrameContext will be initialised for the frame and
> + * returned to the caller if it was not already initialised.
> + *
> + * If the FrameContext was already initialized for this sequence, a warning will
> + * be reported and the previously initialized FrameContext is returned.
> + *
> + * \return A reference to the FrameContext for sequence \a frame
> + */
> +
> +/**
> + * \fn FCQueue::get()
> + * \brief Obtain the Frame Context at slot specified by \a frame
> + * \param[in] frame The frame context sequence number
> + *
> + * Obtains an existing FrameContext from the queue and returns it to the caller.
> + *
> + * If the FrameContext is not correctly intiialised for the \a frame, it will be
s/intiialised/initialised/
> + * initialised and a PFCError will be flagged on the context to be transferred
> + * to the Request when it completes.
> + *
> + * \return A reference to the FrameContext for sequence \a frame
> + */
> +
> +} /* namespace ipa */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/libipa/fc_queue.h b/src/ipa/libipa/fc_queue.h
> new file mode 100644
> index 000000000000..82ce36811926
> --- /dev/null
> +++ b/src/ipa/libipa/fc_queue.h
> @@ -0,0 +1,93 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2022, Google Inc.
> + *
> + * fc_queue.h - IPA Frame context queue
> + *
> + */
> +
> +#pragma once
> +
> +#include <array>
> +
> +#include <libcamera/base/log.h>
> +
> +#include <libcamera/controls.h>
> +
> +namespace libcamera {
> +
> +LOG_DECLARE_CATEGORY(FCQueue)
> +
> +namespace ipa {
> +
> +/*
> + * Maximum number of frame contexts to be held onto
> + *
> + * \todo Should be larger than ISP delay + sensor delay
> + */
> +static constexpr uint32_t kMaxFrameContexts = 16;
> +
> +template<typename FrameContext>

Nice, templates wohoo!

> +class FCQueue : public std::array<FrameContext, kMaxFrameContexts>


Private inheritance will be required. We don't want to expose std::array 
APIs to get used accidentally.

> +{
> +private:
> +	void initialise(FrameContext &frameContext, const uint32_t frame)
> +	{
> +		frameContext = {};
> +		frameContext.frame = frame;
> +	}
> +
> +public:
> +	void clear()
> +	{
> +		this->fill({});
> +	}
> +
> +	FrameContext &initialise(const uint32_t frame)
> +	{
> +		FrameContext &frameContext = this->at(frame & kMaxFrameContexts);
> +
> +		/*
> +		 * Do not re-initialise if a get() call has already fetched this
> +		 * frame context to preseve the error flags already raised.
> +		 */
> +		if (frame == frameContext.frame && frame != 0) {
> +			LOG(FCQueue, Warning)
> +				<< "Frame " << frame << " already initialised";
> +		} else {
> +			initialise(frameContext, frame);
> +		}
> +
> +		return frameContext;
> +	}
> +
> +	FrameContext &get(uint32_t frame)
> +	{
> +		FrameContext &frameContext = this->at(frame & kMaxFrameContexts);
> +
> +		if (frame != frameContext.frame) {
> +			LOG(FCQueue, Warning)
> +				<< "Obtained an uninitialised FrameContext for "
> +				<< frame;
> +
> +			initialise(frameContext, frame);
> +
> +			/*
> +			 * The frame context has been retrieved before it was
> +			 * initialised through the initialise() call. This
> +			 * indicates an algorithm attempted to access a Frame
> +			 * context before it was queued to the IPA.
> +			 *
> +			 * Controls applied for this request may be left
> +			 * unhandled.
> +			 */
> +			frameContext.error |= Request::PFCError;
> +		}
> +
> +		return frameContext;
> +	}
> +};


For now, it looks more or less as per stated in the design.

Thank you for the work!

> +
> +} /* namespace ipa */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/libipa/meson.build b/src/ipa/libipa/meson.build
> index fb894bc614af..016b8e0ec9be 100644
> --- a/src/ipa/libipa/meson.build
> +++ b/src/ipa/libipa/meson.build
> @@ -3,6 +3,7 @@
>   libipa_headers = files([
>       'algorithm.h',
>       'camera_sensor_helper.h',
> +    'fc_queue.h',
>       'histogram.h',
>       'module.h',
>   ])
> @@ -10,6 +11,7 @@ libipa_headers = files([
>   libipa_sources = files([
>       'algorithm.cpp',
>       'camera_sensor_helper.cpp',
> +    'fc_queue.cpp',
>       'histogram.cpp',
>       'module.cpp',
>   ])

Hi Kieran,
  one comment on the class implementation before doing a full review

On Thu, Jul 21, 2022 at 01:13:02PM +0100, Kieran Bingham via libcamera-devel wrote:
> From: Umang Jain <umang.jain@ideasonboard.com>
>
> Provide a direct FCQueue abstraction to facilitate creating a queue of
> Frame Context structures.
>
> The IPAFrameContext is moved back to the ipu3/ipa_context.h and a queue
> added to the IPU3, but the Algorithms are not yet moved from the single
> FrameContext exposed by the IPA context to use the correct one from the
> queue until the Algorithm interfaces are fully updated.
>
> Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> ---
>  src/ipa/ipu3/ipa_context.cpp | 17 -------
>  src/ipa/ipu3/ipa_context.h   | 15 ++----
>  src/ipa/ipu3/ipu3.cpp        | 13 +++--
>  src/ipa/libipa/fc_queue.cpp  | 96 ++++++++++++++++++++++++++++++++++++
>  src/ipa/libipa/fc_queue.h    | 93 ++++++++++++++++++++++++++++++++++
>  src/ipa/libipa/meson.build   |  2 +
>  6 files changed, 204 insertions(+), 32 deletions(-)
>  create mode 100644 src/ipa/libipa/fc_queue.cpp
>  create mode 100644 src/ipa/libipa/fc_queue.h
>
> diff --git a/src/ipa/ipu3/ipa_context.cpp b/src/ipa/ipu3/ipa_context.cpp
> index 13cdb835ef7f..dd139cb4c868 100644
> --- a/src/ipa/ipu3/ipa_context.cpp
> +++ b/src/ipa/ipu3/ipa_context.cpp
> @@ -180,27 +180,10 @@ namespace libcamera::ipa::ipu3 {
>   * <linux/intel-ipu3.h> struct ipu3_uapi_gamma_corr_lut for further details.
>   */
>
> -/**
> - * \brief Default constructor for IPAFrameContext
> - */
> -IPAFrameContext::IPAFrameContext() = default;
> -
> -/**
> - * \brief Construct a IPAFrameContext instance
> - */
> -IPAFrameContext::IPAFrameContext(uint32_t id, const ControlList &reqControls)
> -	: frame(id), frameControls(reqControls)
> -{
> -	sensor = {};
> -}
> -
>  /**
>   * \var IPAFrameContext::frame
>   * \brief The frame number
>   *
> - * \var IPAFrameContext::frameControls
> - * \brief Controls sent in by the application while queuing the request
> - *
>   * \var IPAFrameContext::sensor
>   * \brief Effective sensor values that were applied for the frame
>   *
> diff --git a/src/ipa/ipu3/ipa_context.h b/src/ipa/ipu3/ipa_context.h
> index 42e11141d3a1..193fc44a821a 100644
> --- a/src/ipa/ipu3/ipa_context.h
> +++ b/src/ipa/ipu3/ipa_context.h
> @@ -8,8 +8,6 @@
>
>  #pragma once
>
> -#include <array>
> -
>  #include <linux/intel-ipu3.h>
>
>  #include <libcamera/base/utils.h>
> @@ -17,13 +15,12 @@
>  #include <libcamera/controls.h>
>  #include <libcamera/geometry.h>
>
> +#include <libipa/fc_queue.h>
> +
>  namespace libcamera {
>
>  namespace ipa::ipu3 {
>
> -/* Maximum number of frame contexts to be held */
> -static constexpr uint32_t kMaxFrameContexts = 16;
> -
>  struct IPASessionConfiguration {
>  	struct {
>  		ipu3_uapi_grid_config bdsGrid;
> @@ -77,23 +74,19 @@ struct IPAActiveState {
>  };
>
>  struct IPAFrameContext {
> -	IPAFrameContext();
> -	IPAFrameContext(uint32_t id, const ControlList &reqControls);
> +	uint32_t frame;
>
>  	struct {
>  		uint32_t exposure;
>  		double gain;
>  	} sensor;
> -
> -	uint32_t frame;
> -	ControlList frameControls;
>  };
>
>  struct IPAContext {
>  	IPASessionConfiguration configuration;
>  	IPAActiveState activeState;
>
> -	std::array<IPAFrameContext, kMaxFrameContexts> frameContexts;
> +	FCQueue<IPAFrameContext> frameContexts;
>  };
>
>  } /* namespace ipa::ipu3 */
> diff --git a/src/ipa/ipu3/ipu3.cpp b/src/ipa/ipu3/ipu3.cpp
> index 2f6bb672f7bb..55e82cd404f4 100644
> --- a/src/ipa/ipu3/ipu3.cpp
> +++ b/src/ipa/ipu3/ipu3.cpp
> @@ -38,6 +38,8 @@
>  #include "algorithms/tone_mapping.h"
>  #include "libipa/camera_sensor_helper.h"
>
> +#include "ipa_context.h"
> +
>  /* Minimum grid width, expressed as a number of cells */
>  static constexpr uint32_t kMinGridWidth = 16;
>  /* Maximum grid width, expressed as a number of cells */
> @@ -456,8 +458,7 @@ int IPAIPU3::configure(const IPAConfigInfo &configInfo,
>
>  	/* Clean IPAActiveState at each reconfiguration. */
>  	context_.activeState = {};
> -	IPAFrameContext initFrameContext;
> -	context_.frameContexts.fill(initFrameContext);
> +	context_.frameContexts.clear();
>
>  	if (!validateSensorControls()) {
>  		LOG(IPAIPU3, Error) << "Sensor control validation failed.";
> @@ -569,7 +570,7 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
>  	const ipu3_uapi_stats_3a *stats =
>  		reinterpret_cast<ipu3_uapi_stats_3a *>(mem.data());
>
> -	IPAFrameContext &frameContext = context_.frameContexts[frame % kMaxFrameContexts];
> +	IPAFrameContext &frameContext = context_.frameContexts.get(frame);
>
>  	if (frameContext.frame != frame)
>  		LOG(IPAIPU3, Warning) << "Frame " << frame << " does not match its frame context";
> @@ -618,7 +619,11 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
>  void IPAIPU3::queueRequest(const uint32_t frame, const ControlList &controls)
>  {
>  	/* \todo Start processing for 'frame' based on 'controls'. */
> -	context_.frameContexts[frame % kMaxFrameContexts] = { frame, controls };
> +	IPAFrameContext &frameContext = context_.frameContexts.initialise(frame);
> +
> +	/* \todo Implement queueRequest to each algorithm. */
> +	(void)frameContext;
> +	(void)controls;
>  }
>
>  /**
> diff --git a/src/ipa/libipa/fc_queue.cpp b/src/ipa/libipa/fc_queue.cpp
> new file mode 100644
> index 000000000000..ecb47f287350
> --- /dev/null
> +++ b/src/ipa/libipa/fc_queue.cpp
> @@ -0,0 +1,96 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2022, Google Inc.
> + *
> + * fc_queue.cpp - IPA Frame context queue
> + */
> +
> +#include "fc_queue.h"
> +
> +#include <libcamera/base/log.h>
> +
> +namespace libcamera {
> +
> +LOG_DEFINE_CATEGORY(FCQueue)
> +
> +namespace ipa {
> +
> +/**
> + * \file fc_queue.h
> + * \brief Queue to access per-frame Context
> + */
> +
> +/**
> + * \class FCQueue
> + * \brief A support class for queueing Frame Context instances through the IPA
> + * \tparam FrameContext The IPA specific Frame Context type for this queue
> + *
> + * The Frame Context Queue provides a simple circular buffer implementation to
> + * store IPA specific context for each frame through its lifetime within the
> + * IPA.
> + *
> + * FrameContexts are expected to be referenced by a monotonically increasing
> + * sequence count referring to a Frame sequence.
> + *
> + * A FrameContext is initialised for a given frame when the corresponding
> + * Request is first queued into the IPA. From that point on the FrameContext can
> + * be obtained by the IPA and its algorithms by referencing it from the frame
> + * sequence number.
> + *
> + * A frame sequence number from the image source must correspond to the request
> + * sequence number for this implementation to be supported in an IPA. It is
> + * expected that the same sequence number will be used to reference the context
> + * of the Frame from the point of queueing the request, specifying controls for
> + * a given frame, and processing of any ISP related controls and statistics for
> + * the same corresponding image.
> + *
> + * IPA specific FrameContexts should inherit from the IPAFrameContext to support
> + * the minimum required features for a FrameContext, including the frame number
> + * and error flags that relate to the frame.
> + *
> + * FrameContexts are overwritten when they are recycled and re-initialised by
> + * the first access made on them by either initialise(frame) or get(frame). If a
> + * FrameContext is first accessed through get(frame) before calling initialise()
> + * a PFCError is automatically raised on the FrameContext to be transferred to
> + * the Request when it completes.
> + */
> +
> +/**
> + * \fn FCQueue::clear()
> + * \brief Reinitialise all data on the queue
> + *
> + * Reset the queue and ensure all FrameContext slots are re-initialised.
> + */
> +
> +/**
> + * \fn FCQueue::initialise(uint32_t frame)
> + * \brief Initialize and return the Frame Context at slot specified by \a frame
> + * \param[in] frame The frame context sequence number
> + *
> + * The first call to obtain a FrameContext from the FCQueue should be handled
> + * through this call. The FrameContext will be initialised for the frame and
> + * returned to the caller if it was not already initialised.
> + *
> + * If the FrameContext was already initialized for this sequence, a warning will
> + * be reported and the previously initialized FrameContext is returned.
> + *
> + * \return A reference to the FrameContext for sequence \a frame
> + */
> +
> +/**
> + * \fn FCQueue::get()
> + * \brief Obtain the Frame Context at slot specified by \a frame
> + * \param[in] frame The frame context sequence number
> + *
> + * Obtains an existing FrameContext from the queue and returns it to the caller.
> + *
> + * If the FrameContext is not correctly intiialised for the \a frame, it will be
> + * initialised and a PFCError will be flagged on the context to be transferred
> + * to the Request when it completes.
> + *
> + * \return A reference to the FrameContext for sequence \a frame
> + */
> +
> +} /* namespace ipa */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/libipa/fc_queue.h b/src/ipa/libipa/fc_queue.h
> new file mode 100644
> index 000000000000..82ce36811926
> --- /dev/null
> +++ b/src/ipa/libipa/fc_queue.h
> @@ -0,0 +1,93 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2022, Google Inc.
> + *
> + * fc_queue.h - IPA Frame context queue
> + *
> + */
> +
> +#pragma once
> +
> +#include <array>
> +
> +#include <libcamera/base/log.h>
> +
> +#include <libcamera/controls.h>
> +
> +namespace libcamera {
> +
> +LOG_DECLARE_CATEGORY(FCQueue)
> +
> +namespace ipa {
> +
> +/*
> + * Maximum number of frame contexts to be held onto
> + *
> + * \todo Should be larger than ISP delay + sensor delay
> + */
> +static constexpr uint32_t kMaxFrameContexts = 16;
> +
> +template<typename FrameContext>

I presume the idea of using a template is to allow IPAs to define
their own frame context and use this class as a container.

However the class assumes that the FrameContext template argument has
a well defined interface, specifically it requires a 'uint32_t frame'
field.

There is no guarantee at all that the class used to instantiate the
template has such field with the here proposed design, am I wrong ?

Shouldn't we create a base class in libipa such as:

class IPAFrameContext
{
public:
        uint32_t frame = 0;
};

And let IPA implementation subclass it ?

Can we force it to be a pure virtual class by making the constructor
virtual ? There might be some more clever ways to make this a
non-instantiable interface...

How to force the FCQueue to nicely accept a class derived from
IPAFrameContext might also require some thinking, but I presume we
might want enforce that ?

> +class FCQueue : public std::array<FrameContext, kMaxFrameContexts>
> +{
> +private:
> +	void initialise(FrameContext &frameContext, const uint32_t frame)
> +	{
> +		frameContext = {};
> +		frameContext.frame = frame;
> +	}
> +
> +public:
> +	void clear()
> +	{
> +		this->fill({});
> +	}
> +
> +	FrameContext &initialise(const uint32_t frame)
> +	{
> +		FrameContext &frameContext = this->at(frame & kMaxFrameContexts);
> +
> +		/*
> +		 * Do not re-initialise if a get() call has already fetched this
> +		 * frame context to preseve the error flags already raised.
> +		 */
> +		if (frame == frameContext.frame && frame != 0) {
> +			LOG(FCQueue, Warning)
> +				<< "Frame " << frame << " already initialised";
> +		} else {
> +			initialise(frameContext, frame);
> +		}
> +
> +		return frameContext;
> +	}
> +
> +	FrameContext &get(uint32_t frame)
> +	{
> +		FrameContext &frameContext = this->at(frame & kMaxFrameContexts);
> +
> +		if (frame != frameContext.frame) {
> +			LOG(FCQueue, Warning)
> +				<< "Obtained an uninitialised FrameContext for "
> +				<< frame;
> +
> +			initialise(frameContext, frame);
> +
> +			/*
> +			 * The frame context has been retrieved before it was
> +			 * initialised through the initialise() call. This
> +			 * indicates an algorithm attempted to access a Frame
> +			 * context before it was queued to the IPA.
> +			 *
> +			 * Controls applied for this request may be left
> +			 * unhandled.
> +			 */
> +			frameContext.error |= Request::PFCError;
> +		}
> +
> +		return frameContext;
> +	}
> +};
> +
> +} /* namespace ipa */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/libipa/meson.build b/src/ipa/libipa/meson.build
> index fb894bc614af..016b8e0ec9be 100644
> --- a/src/ipa/libipa/meson.build
> +++ b/src/ipa/libipa/meson.build
> @@ -3,6 +3,7 @@
>  libipa_headers = files([
>      'algorithm.h',
>      'camera_sensor_helper.h',
> +    'fc_queue.h',
>      'histogram.h',
>      'module.h',
>  ])
> @@ -10,6 +11,7 @@ libipa_headers = files([
>  libipa_sources = files([
>      'algorithm.cpp',
>      'camera_sensor_helper.cpp',
> +    'fc_queue.cpp',
>      'histogram.cpp',
>      'module.cpp',
>  ])
> --
> 2.34.1
>

One additional note

On Mon, Jul 25, 2022 at 10:29:17AM +0200, Jacopo Mondi via libcamera-devel wrote:
> Hi Kieran,
>   one comment on the class implementation before doing a full review
>
> On Thu, Jul 21, 2022 at 01:13:02PM +0100, Kieran Bingham via libcamera-devel wrote:
> > From: Umang Jain <umang.jain@ideasonboard.com>
> >
> > Provide a direct FCQueue abstraction to facilitate creating a queue of
> > Frame Context structures.
> >
> > The IPAFrameContext is moved back to the ipu3/ipa_context.h and a queue
> > added to the IPU3, but the Algorithms are not yet moved from the single
> > FrameContext exposed by the IPA context to use the correct one from the
> > queue until the Algorithm interfaces are fully updated.
> >
> > Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
> > Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> > ---
> >  src/ipa/ipu3/ipa_context.cpp | 17 -------
> >  src/ipa/ipu3/ipa_context.h   | 15 ++----
> >  src/ipa/ipu3/ipu3.cpp        | 13 +++--
> >  src/ipa/libipa/fc_queue.cpp  | 96 ++++++++++++++++++++++++++++++++++++
> >  src/ipa/libipa/fc_queue.h    | 93 ++++++++++++++++++++++++++++++++++
> >  src/ipa/libipa/meson.build   |  2 +
> >  6 files changed, 204 insertions(+), 32 deletions(-)
> >  create mode 100644 src/ipa/libipa/fc_queue.cpp
> >  create mode 100644 src/ipa/libipa/fc_queue.h
> >
> > diff --git a/src/ipa/ipu3/ipa_context.cpp b/src/ipa/ipu3/ipa_context.cpp
> > index 13cdb835ef7f..dd139cb4c868 100644
> > --- a/src/ipa/ipu3/ipa_context.cpp
> > +++ b/src/ipa/ipu3/ipa_context.cpp
> > @@ -180,27 +180,10 @@ namespace libcamera::ipa::ipu3 {
> >   * <linux/intel-ipu3.h> struct ipu3_uapi_gamma_corr_lut for further details.
> >   */
> >
> > -/**
> > - * \brief Default constructor for IPAFrameContext
> > - */
> > -IPAFrameContext::IPAFrameContext() = default;
> > -
> > -/**
> > - * \brief Construct a IPAFrameContext instance
> > - */
> > -IPAFrameContext::IPAFrameContext(uint32_t id, const ControlList &reqControls)
> > -	: frame(id), frameControls(reqControls)
> > -{
> > -	sensor = {};
> > -}
> > -
> >  /**
> >   * \var IPAFrameContext::frame
> >   * \brief The frame number
> >   *
> > - * \var IPAFrameContext::frameControls
> > - * \brief Controls sent in by the application while queuing the request
> > - *
> >   * \var IPAFrameContext::sensor
> >   * \brief Effective sensor values that were applied for the frame
> >   *
> > diff --git a/src/ipa/ipu3/ipa_context.h b/src/ipa/ipu3/ipa_context.h
> > index 42e11141d3a1..193fc44a821a 100644
> > --- a/src/ipa/ipu3/ipa_context.h
> > +++ b/src/ipa/ipu3/ipa_context.h
> > @@ -8,8 +8,6 @@
> >
> >  #pragma once
> >
> > -#include <array>
> > -
> >  #include <linux/intel-ipu3.h>
> >
> >  #include <libcamera/base/utils.h>
> > @@ -17,13 +15,12 @@
> >  #include <libcamera/controls.h>
> >  #include <libcamera/geometry.h>
> >
> > +#include <libipa/fc_queue.h>
> > +
> >  namespace libcamera {
> >
> >  namespace ipa::ipu3 {
> >
> > -/* Maximum number of frame contexts to be held */
> > -static constexpr uint32_t kMaxFrameContexts = 16;
> > -
> >  struct IPASessionConfiguration {
> >  	struct {
> >  		ipu3_uapi_grid_config bdsGrid;
> > @@ -77,23 +74,19 @@ struct IPAActiveState {
> >  };
> >
> >  struct IPAFrameContext {
> > -	IPAFrameContext();
> > -	IPAFrameContext(uint32_t id, const ControlList &reqControls);
> > +	uint32_t frame;
> >
> >  	struct {
> >  		uint32_t exposure;
> >  		double gain;
> >  	} sensor;
> > -
> > -	uint32_t frame;
> > -	ControlList frameControls;
> >  };
> >
> >  struct IPAContext {
> >  	IPASessionConfiguration configuration;
> >  	IPAActiveState activeState;
> >
> > -	std::array<IPAFrameContext, kMaxFrameContexts> frameContexts;
> > +	FCQueue<IPAFrameContext> frameContexts;
> >  };
> >
> >  } /* namespace ipa::ipu3 */
> > diff --git a/src/ipa/ipu3/ipu3.cpp b/src/ipa/ipu3/ipu3.cpp
> > index 2f6bb672f7bb..55e82cd404f4 100644
> > --- a/src/ipa/ipu3/ipu3.cpp
> > +++ b/src/ipa/ipu3/ipu3.cpp
> > @@ -38,6 +38,8 @@
> >  #include "algorithms/tone_mapping.h"
> >  #include "libipa/camera_sensor_helper.h"
> >
> > +#include "ipa_context.h"
> > +
> >  /* Minimum grid width, expressed as a number of cells */
> >  static constexpr uint32_t kMinGridWidth = 16;
> >  /* Maximum grid width, expressed as a number of cells */
> > @@ -456,8 +458,7 @@ int IPAIPU3::configure(const IPAConfigInfo &configInfo,
> >
> >  	/* Clean IPAActiveState at each reconfiguration. */
> >  	context_.activeState = {};
> > -	IPAFrameContext initFrameContext;
> > -	context_.frameContexts.fill(initFrameContext);
> > +	context_.frameContexts.clear();
> >
> >  	if (!validateSensorControls()) {
> >  		LOG(IPAIPU3, Error) << "Sensor control validation failed.";
> > @@ -569,7 +570,7 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
> >  	const ipu3_uapi_stats_3a *stats =
> >  		reinterpret_cast<ipu3_uapi_stats_3a *>(mem.data());
> >
> > -	IPAFrameContext &frameContext = context_.frameContexts[frame % kMaxFrameContexts];
> > +	IPAFrameContext &frameContext = context_.frameContexts.get(frame);
> >
> >  	if (frameContext.frame != frame)
> >  		LOG(IPAIPU3, Warning) << "Frame " << frame << " does not match its frame context";
> > @@ -618,7 +619,11 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
> >  void IPAIPU3::queueRequest(const uint32_t frame, const ControlList &controls)
> >  {
> >  	/* \todo Start processing for 'frame' based on 'controls'. */
> > -	context_.frameContexts[frame % kMaxFrameContexts] = { frame, controls };
> > +	IPAFrameContext &frameContext = context_.frameContexts.initialise(frame);
> > +
> > +	/* \todo Implement queueRequest to each algorithm. */
> > +	(void)frameContext;
> > +	(void)controls;
> >  }
> >
> >  /**
> > diff --git a/src/ipa/libipa/fc_queue.cpp b/src/ipa/libipa/fc_queue.cpp
> > new file mode 100644
> > index 000000000000..ecb47f287350
> > --- /dev/null
> > +++ b/src/ipa/libipa/fc_queue.cpp
> > @@ -0,0 +1,96 @@
> > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > +/*
> > + * Copyright (C) 2022, Google Inc.
> > + *
> > + * fc_queue.cpp - IPA Frame context queue
> > + */
> > +
> > +#include "fc_queue.h"
> > +
> > +#include <libcamera/base/log.h>
> > +
> > +namespace libcamera {
> > +
> > +LOG_DEFINE_CATEGORY(FCQueue)
> > +
> > +namespace ipa {
> > +
> > +/**
> > + * \file fc_queue.h
> > + * \brief Queue to access per-frame Context
> > + */
> > +
> > +/**
> > + * \class FCQueue
> > + * \brief A support class for queueing Frame Context instances through the IPA
> > + * \tparam FrameContext The IPA specific Frame Context type for this queue
> > + *
> > + * The Frame Context Queue provides a simple circular buffer implementation to
> > + * store IPA specific context for each frame through its lifetime within the
> > + * IPA.
> > + *
> > + * FrameContexts are expected to be referenced by a monotonically increasing
> > + * sequence count referring to a Frame sequence.
> > + *
> > + * A FrameContext is initialised for a given frame when the corresponding
> > + * Request is first queued into the IPA. From that point on the FrameContext can
> > + * be obtained by the IPA and its algorithms by referencing it from the frame
> > + * sequence number.
> > + *
> > + * A frame sequence number from the image source must correspond to the request
> > + * sequence number for this implementation to be supported in an IPA. It is
> > + * expected that the same sequence number will be used to reference the context
> > + * of the Frame from the point of queueing the request, specifying controls for
> > + * a given frame, and processing of any ISP related controls and statistics for
> > + * the same corresponding image.
> > + *
> > + * IPA specific FrameContexts should inherit from the IPAFrameContext to support
> > + * the minimum required features for a FrameContext, including the frame number
> > + * and error flags that relate to the frame.
> > + *
> > + * FrameContexts are overwritten when they are recycled and re-initialised by
> > + * the first access made on them by either initialise(frame) or get(frame). If a
> > + * FrameContext is first accessed through get(frame) before calling initialise()
> > + * a PFCError is automatically raised on the FrameContext to be transferred to
> > + * the Request when it completes.
> > + */
> > +
> > +/**
> > + * \fn FCQueue::clear()
> > + * \brief Reinitialise all data on the queue
> > + *
> > + * Reset the queue and ensure all FrameContext slots are re-initialised.
> > + */
> > +
> > +/**
> > + * \fn FCQueue::initialise(uint32_t frame)
> > + * \brief Initialize and return the Frame Context at slot specified by \a frame
> > + * \param[in] frame The frame context sequence number
> > + *
> > + * The first call to obtain a FrameContext from the FCQueue should be handled
> > + * through this call. The FrameContext will be initialised for the frame and
> > + * returned to the caller if it was not already initialised.
> > + *
> > + * If the FrameContext was already initialized for this sequence, a warning will
> > + * be reported and the previously initialized FrameContext is returned.
> > + *
> > + * \return A reference to the FrameContext for sequence \a frame
> > + */
> > +
> > +/**
> > + * \fn FCQueue::get()
> > + * \brief Obtain the Frame Context at slot specified by \a frame
> > + * \param[in] frame The frame context sequence number
> > + *
> > + * Obtains an existing FrameContext from the queue and returns it to the caller.
> > + *
> > + * If the FrameContext is not correctly intiialised for the \a frame, it will be
> > + * initialised and a PFCError will be flagged on the context to be transferred
> > + * to the Request when it completes.
> > + *
> > + * \return A reference to the FrameContext for sequence \a frame
> > + */
> > +
> > +} /* namespace ipa */
> > +
> > +} /* namespace libcamera */
> > diff --git a/src/ipa/libipa/fc_queue.h b/src/ipa/libipa/fc_queue.h
> > new file mode 100644
> > index 000000000000..82ce36811926
> > --- /dev/null
> > +++ b/src/ipa/libipa/fc_queue.h
> > @@ -0,0 +1,93 @@
> > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > +/*
> > + * Copyright (C) 2022, Google Inc.
> > + *
> > + * fc_queue.h - IPA Frame context queue
> > + *
> > + */
> > +
> > +#pragma once
> > +
> > +#include <array>
> > +
> > +#include <libcamera/base/log.h>
> > +
> > +#include <libcamera/controls.h>
> > +
> > +namespace libcamera {
> > +
> > +LOG_DECLARE_CATEGORY(FCQueue)
> > +
> > +namespace ipa {
> > +
> > +/*
> > + * Maximum number of frame contexts to be held onto
> > + *
> > + * \todo Should be larger than ISP delay + sensor delay
> > + */
> > +static constexpr uint32_t kMaxFrameContexts = 16;
> > +
> > +template<typename FrameContext>
>
> I presume the idea of using a template is to allow IPAs to define
> their own frame context and use this class as a container.
>
> However the class assumes that the FrameContext template argument has
> a well defined interface, specifically it requires a 'uint32_t frame'
> field.
>
> There is no guarantee at all that the class used to instantiate the
> template has such field with the here proposed design, am I wrong ?
>
> Shouldn't we create a base class in libipa such as:
>
> class IPAFrameContext
> {
> public:
>         uint32_t frame = 0;
> };
>
> And let IPA implementation subclass it ?

This happens later :)
>
> Can we force it to be a pure virtual class by making the constructor
> virtual ? There might be some more clever ways to make this a
> non-instantiable interface...
>
> How to force the FCQueue to nicely accept a class derived from
> IPAFrameContext might also require some thinking, but I presume we
> might want enforce that ?
>

Please also note that is a non-problem as to my surprise the templates
argument substitution compile-time checks if the provided type matches
the requested interface. The C++ templating system does duck typing
and if the provided FrameContext template argument does not inherit
from IPAFrameContext it breaks with:

../src/ipa/ipu3/ipu3.cpp:577:26: error: ‘struct libcamera::ipa::ipu3::IPU3FrameContext’ has no member named ‘frame’
  577 |         if (frameContext.frame != frame)
      |                          ^~~~~

However we can exploit std::type_traits to more explicitly check for the
FrameContext template argument to be a derived class of
IPAFrameContext with:

template<typename FrameContext>
class FCQueue : public std::array<FrameContext, kMaxFrameContexts>
{
private:
	using valueType =
		std::enable_if_t<std::is_base_of_v<IPAFrameContext, FrameContext>,
				 FrameContext>;

However the error message, in case FrameContext does not inherit from
IPAFrameContext, is not much more helpful I'm afraid

/usr/include/c++/12.1.0/type_traits: In substitution of ‘template<bool _Cond, class _Tp> using enable_if_t = typename std::enable_if::type [with bool _Cond = false; _Tp = libcamera::ipa::ipu3::IPU3FrameContext]’:
../src/ipa/libipa/fc_queue.h:41:8:   required from ‘class libcamera::ipa::FCQueue<libcamera::ipa::ipu3::IPU3FrameContext>’
../src/ipa/ipu3/ipa_context.h:88:28:   required from here
/usr/include/c++/12.1.0/type_traits:2614:11: error: no type named ‘type’ in ‘struct std::enable_if<false, libcamera::ipa::ipu3::IPU3FrameContext>’
 2614 |     using enable_if_t = typename enable_if<_Cond, _Tp>::type;

But could help pointing to the source file where a comment might
explain the required inheritance.

Anyway, as it breaks at compile time, this is a minor nit indeed


> > +class FCQueue : public std::array<FrameContext, kMaxFrameContexts>
> > +{
> > +private:
> > +	void initialise(FrameContext &frameContext, const uint32_t frame)
> > +	{
> > +		frameContext = {};
> > +		frameContext.frame = frame;
> > +	}
> > +
> > +public:
> > +	void clear()
> > +	{
> > +		this->fill({});
> > +	}
> > +
> > +	FrameContext &initialise(const uint32_t frame)
> > +	{
> > +		FrameContext &frameContext = this->at(frame & kMaxFrameContexts);
> > +
> > +		/*
> > +		 * Do not re-initialise if a get() call has already fetched this
> > +		 * frame context to preseve the error flags already raised.
> > +		 */
> > +		if (frame == frameContext.frame && frame != 0) {
> > +			LOG(FCQueue, Warning)
> > +				<< "Frame " << frame << " already initialised";
> > +		} else {
> > +			initialise(frameContext, frame);
> > +		}
> > +
> > +		return frameContext;
> > +	}
> > +
> > +	FrameContext &get(uint32_t frame)
> > +	{
> > +		FrameContext &frameContext = this->at(frame & kMaxFrameContexts);
> > +
> > +		if (frame != frameContext.frame) {
> > +			LOG(FCQueue, Warning)
> > +				<< "Obtained an uninitialised FrameContext for "
> > +				<< frame;
> > +
> > +			initialise(frameContext, frame);
> > +
> > +			/*
> > +			 * The frame context has been retrieved before it was
> > +			 * initialised through the initialise() call. This
> > +			 * indicates an algorithm attempted to access a Frame
> > +			 * context before it was queued to the IPA.
> > +			 *
> > +			 * Controls applied for this request may be left
> > +			 * unhandled.
> > +			 */
> > +			frameContext.error |= Request::PFCError;
> > +		}
> > +
> > +		return frameContext;
> > +	}
> > +};
> > +
> > +} /* namespace ipa */
> > +
> > +} /* namespace libcamera */
> > diff --git a/src/ipa/libipa/meson.build b/src/ipa/libipa/meson.build
> > index fb894bc614af..016b8e0ec9be 100644
> > --- a/src/ipa/libipa/meson.build
> > +++ b/src/ipa/libipa/meson.build
> > @@ -3,6 +3,7 @@
> >  libipa_headers = files([
> >      'algorithm.h',
> >      'camera_sensor_helper.h',
> > +    'fc_queue.h',
> >      'histogram.h',
> >      'module.h',
> >  ])
> > @@ -10,6 +11,7 @@ libipa_headers = files([
> >  libipa_sources = files([
> >      'algorithm.cpp',
> >      'camera_sensor_helper.cpp',
> > +    'fc_queue.cpp',
> >      'histogram.cpp',
> >      'module.cpp',
> >  ])
> > --
> > 2.34.1
> >

Hi Kieran

On Thu, Jul 21, 2022 at 01:13:02PM +0100, Kieran Bingham via libcamera-devel wrote:
> From: Umang Jain <umang.jain@ideasonboard.com>
>
> Provide a direct FCQueue abstraction to facilitate creating a queue of
> Frame Context structures.
>
> The IPAFrameContext is moved back to the ipu3/ipa_context.h and a queue
> added to the IPU3, but the Algorithms are not yet moved from the single
> FrameContext exposed by the IPA context to use the correct one from the
> queue until the Algorithm interfaces are fully updated.
>
> Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> ---
>  src/ipa/ipu3/ipa_context.cpp | 17 -------
>  src/ipa/ipu3/ipa_context.h   | 15 ++----
>  src/ipa/ipu3/ipu3.cpp        | 13 +++--
>  src/ipa/libipa/fc_queue.cpp  | 96 ++++++++++++++++++++++++++++++++++++
>  src/ipa/libipa/fc_queue.h    | 93 ++++++++++++++++++++++++++++++++++
>  src/ipa/libipa/meson.build   |  2 +
>  6 files changed, 204 insertions(+), 32 deletions(-)
>  create mode 100644 src/ipa/libipa/fc_queue.cpp
>  create mode 100644 src/ipa/libipa/fc_queue.h
>
> diff --git a/src/ipa/ipu3/ipa_context.cpp b/src/ipa/ipu3/ipa_context.cpp
> index 13cdb835ef7f..dd139cb4c868 100644
> --- a/src/ipa/ipu3/ipa_context.cpp
> +++ b/src/ipa/ipu3/ipa_context.cpp
> @@ -180,27 +180,10 @@ namespace libcamera::ipa::ipu3 {
>   * <linux/intel-ipu3.h> struct ipu3_uapi_gamma_corr_lut for further details.
>   */
>
> -/**
> - * \brief Default constructor for IPAFrameContext
> - */
> -IPAFrameContext::IPAFrameContext() = default;
> -
> -/**
> - * \brief Construct a IPAFrameContext instance
> - */
> -IPAFrameContext::IPAFrameContext(uint32_t id, const ControlList &reqControls)
> -	: frame(id), frameControls(reqControls)
> -{
> -	sensor = {};
> -}
> -
>  /**
>   * \var IPAFrameContext::frame
>   * \brief The frame number
>   *
> - * \var IPAFrameContext::frameControls
> - * \brief Controls sent in by the application while queuing the request
> - *
>   * \var IPAFrameContext::sensor
>   * \brief Effective sensor values that were applied for the frame
>   *
> diff --git a/src/ipa/ipu3/ipa_context.h b/src/ipa/ipu3/ipa_context.h
> index 42e11141d3a1..193fc44a821a 100644
> --- a/src/ipa/ipu3/ipa_context.h
> +++ b/src/ipa/ipu3/ipa_context.h
> @@ -8,8 +8,6 @@
>
>  #pragma once
>
> -#include <array>
> -
>  #include <linux/intel-ipu3.h>
>
>  #include <libcamera/base/utils.h>
> @@ -17,13 +15,12 @@
>  #include <libcamera/controls.h>
>  #include <libcamera/geometry.h>
>
> +#include <libipa/fc_queue.h>
> +
>  namespace libcamera {
>
>  namespace ipa::ipu3 {
>
> -/* Maximum number of frame contexts to be held */
> -static constexpr uint32_t kMaxFrameContexts = 16;

The size of the FCQueue should probably come from the IPA
implementation, as different platforms will have a different queue
depth to handle.

It can be made a second template argument.

> -
>  struct IPASessionConfiguration {
>  	struct {
>  		ipu3_uapi_grid_config bdsGrid;
> @@ -77,23 +74,19 @@ struct IPAActiveState {
>  };
>
>  struct IPAFrameContext {
> -	IPAFrameContext();
> -	IPAFrameContext(uint32_t id, const ControlList &reqControls);
> +	uint32_t frame;
>
>  	struct {
>  		uint32_t exposure;
>  		double gain;
>  	} sensor;
> -
> -	uint32_t frame;
> -	ControlList frameControls;
>  };
>
>  struct IPAContext {
>  	IPASessionConfiguration configuration;
>  	IPAActiveState activeState;
>
> -	std::array<IPAFrameContext, kMaxFrameContexts> frameContexts;
> +	FCQueue<IPAFrameContext> frameContexts;
>  };
>
>  } /* namespace ipa::ipu3 */
> diff --git a/src/ipa/ipu3/ipu3.cpp b/src/ipa/ipu3/ipu3.cpp
> index 2f6bb672f7bb..55e82cd404f4 100644
> --- a/src/ipa/ipu3/ipu3.cpp
> +++ b/src/ipa/ipu3/ipu3.cpp
> @@ -38,6 +38,8 @@
>  #include "algorithms/tone_mapping.h"
>  #include "libipa/camera_sensor_helper.h"
>
> +#include "ipa_context.h"
> +
>  /* Minimum grid width, expressed as a number of cells */
>  static constexpr uint32_t kMinGridWidth = 16;
>  /* Maximum grid width, expressed as a number of cells */
> @@ -456,8 +458,7 @@ int IPAIPU3::configure(const IPAConfigInfo &configInfo,
>
>  	/* Clean IPAActiveState at each reconfiguration. */
>  	context_.activeState = {};
> -	IPAFrameContext initFrameContext;
> -	context_.frameContexts.fill(initFrameContext);
> +	context_.frameContexts.clear();
>
>  	if (!validateSensorControls()) {
>  		LOG(IPAIPU3, Error) << "Sensor control validation failed.";
> @@ -569,7 +570,7 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
>  	const ipu3_uapi_stats_3a *stats =
>  		reinterpret_cast<ipu3_uapi_stats_3a *>(mem.data());
>
> -	IPAFrameContext &frameContext = context_.frameContexts[frame % kMaxFrameContexts];
> +	IPAFrameContext &frameContext = context_.frameContexts.get(frame);
>
>  	if (frameContext.frame != frame)
>  		LOG(IPAIPU3, Warning) << "Frame " << frame << " does not match its frame context";
> @@ -618,7 +619,11 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
>  void IPAIPU3::queueRequest(const uint32_t frame, const ControlList &controls)
>  {
>  	/* \todo Start processing for 'frame' based on 'controls'. */
> -	context_.frameContexts[frame % kMaxFrameContexts] = { frame, controls };
> +	IPAFrameContext &frameContext = context_.frameContexts.initialise(frame);
> +
> +	/* \todo Implement queueRequest to each algorithm. */
> +	(void)frameContext;
> +	(void)controls;

I'm sure this will be expanded later but it could be simplified as

 void IPAIPU3::queueRequest(const uint32_t frame, [[maybe_unused]] const ControlList &controls)
 {
 	/* \todo Start processing for 'frame' based on 'controls'. */
	context_.frameContexts.initialise(frame);
 }

>  }
>
>  /**
> diff --git a/src/ipa/libipa/fc_queue.cpp b/src/ipa/libipa/fc_queue.cpp
> new file mode 100644
> index 000000000000..ecb47f287350
> --- /dev/null
> +++ b/src/ipa/libipa/fc_queue.cpp
> @@ -0,0 +1,96 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2022, Google Inc.
> + *
> + * fc_queue.cpp - IPA Frame context queue
> + */
> +
> +#include "fc_queue.h"
> +
> +#include <libcamera/base/log.h>
> +
> +namespace libcamera {
> +
> +LOG_DEFINE_CATEGORY(FCQueue)

Is this needed here or can be moved to the .h ?

> +
> +namespace ipa {
> +
> +/**
> + * \file fc_queue.h
> + * \brief Queue to access per-frame Context
> + */
> +
> +/**
> + * \class FCQueue
> + * \brief A support class for queueing Frame Context instances through the IPA

frame context or FrameContext, here and in the other parts of the
documentation ?

> + * \tparam FrameContext The IPA specific Frame Context type for this queue
> + *
> + * The Frame Context Queue provides a simple circular buffer implementation to
> + * store IPA specific context for each frame through its lifetime within the
> + * IPA.
> + *
> + * FrameContexts are expected to be referenced by a monotonically increasing
> + * sequence count referring to a Frame sequence.
                                   "Frame sequence number"  ?
> + *
> + * A FrameContext is initialised for a given frame when the corresponding
> + * Request is first queued into the IPA. From that point on the FrameContext can
> + * be obtained by the IPA and its algorithms by referencing it from the frame
> + * sequence number.
> + *
> + * A frame sequence number from the image source must correspond to the request
> + * sequence number for this implementation to be supported in an IPA. It is
> + * expected that the same sequence number will be used to reference the context
> + * of the Frame from the point of queueing the request, specifying controls for
> + * a given frame, and processing of any ISP related controls and statistics for
> + * the same corresponding image.
> + *
> + * IPA specific FrameContexts should inherit from the IPAFrameContext to support

IPA specific frame context implementations shall inherit from the
IPAFrameContext base class to support..

> + * the minimum required features for a FrameContext, including the frame number
> + * and error flags that relate to the frame.
> + *
> + * FrameContexts are overwritten when they are recycled and re-initialised by
> + * the first access made on them by either initialise(frame) or get(frame). If a

That's what a circular array does.

I would rather express the fact that the number of available contexts
is required to be larger than the platform pipeline depth (with a
\todo to reference the property once we have it defined). After
pipelineDepth frames have been processed the FrameContext is recycled
and forever lost.

> + * FrameContext is first accessed through get(frame) before calling initialise()
> + * a PFCError is automatically raised on the FrameContext to be transferred to
> + * the Request when it completes.

This would happen because we have a request underrun, right ?

I would state that. Like:

In the case an application does not queue requests to the Camera fast
enough, frames can be produced and processed by the IPA without a
corresponding Request being queued. In this case the IPA algorithm
will try to access the FrameContext with a call to get() before it
had been initialized at queueRequest() time. In this case there
is now way the controls associated with the late Request could be
applied in time, as the frame as already been processed by the IPA,
the PFCError flag is automatically raised on the FrameContext.

How does it sound ?

> + */
> +
> +/**
> + * \fn FCQueue::clear()
> + * \brief Reinitialise all data on the queue

Or "Clear the queue content" ?

> + *
> + * Reset the queue and ensure all FrameContext slots are re-initialised.

I would add that the Queue has to be re-initialized at every streaming
session start, likely in IPA::configure()

> + */
> +
> +/**
> + * \fn FCQueue::initialise(uint32_t frame)
> + * \brief Initialize and return the Frame Context at slot specified by \a frame
> + * \param[in] frame The frame context sequence number
> + *
> + * The first call to obtain a FrameContext from the FCQueue should be handled
> + * through this call. The FrameContext will be initialised for the frame and
> + * returned to the caller if it was not already initialised.
> + *
> + * If the FrameContext was already initialized for this sequence, a warning will
> + * be reported and the previously initialized FrameContext is returned.
> + *

Should we say it is expected to be called at queueRequest() time ?

> + * \return A reference to the FrameContext for sequence \a frame
> + */
> +
> +/**
> + * \fn FCQueue::get()
> + * \brief Obtain the Frame Context at slot specified by \a frame
> + * \param[in] frame The frame context sequence number
> + *
> + * Obtains an existing FrameContext from the queue and returns it to the caller.
> + *
> + * If the FrameContext is not correctly intiialised for the \a frame, it will be

s/intiialised/initialised/

> + * initialised and a PFCError will be flagged on the context to be transferred
> + * to the Request when it completes.
> + *
> + * \return A reference to the FrameContext for sequence \a frame
> + */
> +
> +} /* namespace ipa */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/libipa/fc_queue.h b/src/ipa/libipa/fc_queue.h
> new file mode 100644
> index 000000000000..82ce36811926
> --- /dev/null
> +++ b/src/ipa/libipa/fc_queue.h
> @@ -0,0 +1,93 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2022, Google Inc.
> + *
> + * fc_queue.h - IPA Frame context queue
> + *

Unecessary empty line

> + */
> +
> +#pragma once
> +
> +#include <array>
> +
> +#include <libcamera/base/log.h>
> +
> +#include <libcamera/controls.h>

Not needed it seems

> +
> +namespace libcamera {
> +
> +LOG_DECLARE_CATEGORY(FCQueue)
> +
> +namespace ipa {
> +
> +/*
> + * Maximum number of frame contexts to be held onto
> + *
> + * \todo Should be larger than ISP delay + sensor delay
> + */
> +static constexpr uint32_t kMaxFrameContexts = 16;
> +
> +template<typename FrameContext>
> +class FCQueue : public std::array<FrameContext, kMaxFrameContexts>
> +{
> +private:
> +	void initialise(FrameContext &frameContext, const uint32_t frame)
> +	{
> +		frameContext = {};
> +		frameContext.frame = frame;
> +	}
> +
> +public:
> +	void clear()
> +	{
> +		this->fill({});
> +	}
> +
> +	FrameContext &initialise(const uint32_t frame)
> +	{
> +		FrameContext &frameContext = this->at(frame & kMaxFrameContexts);
> +
> +		/*
> +		 * Do not re-initialise if a get() call has already fetched this
> +		 * frame context to preseve the error flags already raised.
> +		 */
> +		if (frame == frameContext.frame && frame != 0) {

This should be <= as it needs to catch cases where the frame context
has been possibile overwritten by algorithms calling get() for a
number of times larger than the pipeline depth.

> +			LOG(FCQueue, Warning)
> +				<< "Frame " << frame << " already initialised";
> +		} else {
> +			initialise(frameContext, frame);
> +		}

No brances needed it seems

> +
> +		return frameContext;
> +	}
> +
> +	FrameContext &get(uint32_t frame)
> +	{
> +		FrameContext &frameContext = this->at(frame & kMaxFrameContexts);
> +
> +		if (frame != frameContext.frame) {

Or              if (frame == frameContext.frame)
                        return frameContext;

To save one indentation level. Up to you.

> +			LOG(FCQueue, Warning)
> +				<< "Obtained an uninitialised FrameContext for "
> +				<< frame;
> +
> +			initialise(frameContext, frame);
> +
> +			/*
> +			 * The frame context has been retrieved before it was
> +			 * initialised through the initialise() call. This
> +			 * indicates an algorithm attempted to access a Frame
> +			 * context before it was queued to the IPA.
> +			 *
> +			 * Controls applied for this request may be left
> +			 * unhandled.
> +			 */
> +			frameContext.error |= Request::PFCError;
> +		}
> +
> +		return frameContext;
> +	}
> +};
> +
> +} /* namespace ipa */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/libipa/meson.build b/src/ipa/libipa/meson.build
> index fb894bc614af..016b8e0ec9be 100644
> --- a/src/ipa/libipa/meson.build
> +++ b/src/ipa/libipa/meson.build
> @@ -3,6 +3,7 @@
>  libipa_headers = files([
>      'algorithm.h',
>      'camera_sensor_helper.h',
> +    'fc_queue.h',
>      'histogram.h',
>      'module.h',
>  ])
> @@ -10,6 +11,7 @@ libipa_headers = files([
>  libipa_sources = files([
>      'algorithm.cpp',
>      'camera_sensor_helper.cpp',
> +    'fc_queue.cpp',
>      'histogram.cpp',
>      'module.cpp',
>  ])
> --
> 2.34.1
>

Quoting Jacopo Mondi (2022-07-25 16:20:51)
> Hi Kieran
> 
> On Thu, Jul 21, 2022 at 01:13:02PM +0100, Kieran Bingham via libcamera-devel wrote:
> > From: Umang Jain <umang.jain@ideasonboard.com>
> >
> > Provide a direct FCQueue abstraction to facilitate creating a queue of
> > Frame Context structures.
> >
> > The IPAFrameContext is moved back to the ipu3/ipa_context.h and a queue
> > added to the IPU3, but the Algorithms are not yet moved from the single
> > FrameContext exposed by the IPA context to use the correct one from the
> > queue until the Algorithm interfaces are fully updated.
> >
> > Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
> > Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> > ---
> >  src/ipa/ipu3/ipa_context.cpp | 17 -------
> >  src/ipa/ipu3/ipa_context.h   | 15 ++----
> >  src/ipa/ipu3/ipu3.cpp        | 13 +++--
> >  src/ipa/libipa/fc_queue.cpp  | 96 ++++++++++++++++++++++++++++++++++++
> >  src/ipa/libipa/fc_queue.h    | 93 ++++++++++++++++++++++++++++++++++
> >  src/ipa/libipa/meson.build   |  2 +
> >  6 files changed, 204 insertions(+), 32 deletions(-)
> >  create mode 100644 src/ipa/libipa/fc_queue.cpp
> >  create mode 100644 src/ipa/libipa/fc_queue.h
> >
> > diff --git a/src/ipa/ipu3/ipa_context.cpp b/src/ipa/ipu3/ipa_context.cpp
> > index 13cdb835ef7f..dd139cb4c868 100644
> > --- a/src/ipa/ipu3/ipa_context.cpp
> > +++ b/src/ipa/ipu3/ipa_context.cpp
> > @@ -180,27 +180,10 @@ namespace libcamera::ipa::ipu3 {
> >   * <linux/intel-ipu3.h> struct ipu3_uapi_gamma_corr_lut for further details.
> >   */
> >
> > -/**
> > - * \brief Default constructor for IPAFrameContext
> > - */
> > -IPAFrameContext::IPAFrameContext() = default;
> > -
> > -/**
> > - * \brief Construct a IPAFrameContext instance
> > - */
> > -IPAFrameContext::IPAFrameContext(uint32_t id, const ControlList &reqControls)
> > -     : frame(id), frameControls(reqControls)
> > -{
> > -     sensor = {};
> > -}
> > -
> >  /**
> >   * \var IPAFrameContext::frame
> >   * \brief The frame number
> >   *
> > - * \var IPAFrameContext::frameControls
> > - * \brief Controls sent in by the application while queuing the request
> > - *
> >   * \var IPAFrameContext::sensor
> >   * \brief Effective sensor values that were applied for the frame
> >   *
> > diff --git a/src/ipa/ipu3/ipa_context.h b/src/ipa/ipu3/ipa_context.h
> > index 42e11141d3a1..193fc44a821a 100644
> > --- a/src/ipa/ipu3/ipa_context.h
> > +++ b/src/ipa/ipu3/ipa_context.h
> > @@ -8,8 +8,6 @@
> >
> >  #pragma once
> >
> > -#include <array>
> > -
> >  #include <linux/intel-ipu3.h>
> >
> >  #include <libcamera/base/utils.h>
> > @@ -17,13 +15,12 @@
> >  #include <libcamera/controls.h>
> >  #include <libcamera/geometry.h>
> >
> > +#include <libipa/fc_queue.h>
> > +
> >  namespace libcamera {
> >
> >  namespace ipa::ipu3 {
> >
> > -/* Maximum number of frame contexts to be held */
> > -static constexpr uint32_t kMaxFrameContexts = 16;
> 
> The size of the FCQueue should probably come from the IPA
> implementation, as different platforms will have a different queue
> depth to handle.
> 
> It can be made a second template argument.

Yes, this is absoultely a platform specific value.

I simply haven't made it adjustable yet.

I believe it could also be handled on top, as '16' is bigger than both
expected platforms currently ;-)

I'd rather handle that as a separate patch as well - as whatever size it
is contstructed as needs to be conveyed to the pipeline handler too.

Either the PH should state what size the IPA should make, or otherwise
they should both be hardcoded to the same size.

But that's enough discussion that I think it deserves it's own
patch/implementation.


> > -
> >  struct IPASessionConfiguration {
> >       struct {
> >               ipu3_uapi_grid_config bdsGrid;
> > @@ -77,23 +74,19 @@ struct IPAActiveState {
> >  };
> >
> >  struct IPAFrameContext {
> > -     IPAFrameContext();
> > -     IPAFrameContext(uint32_t id, const ControlList &reqControls);
> > +     uint32_t frame;
> >
> >       struct {
> >               uint32_t exposure;
> >               double gain;
> >       } sensor;
> > -
> > -     uint32_t frame;
> > -     ControlList frameControls;
> >  };
> >
> >  struct IPAContext {
> >       IPASessionConfiguration configuration;
> >       IPAActiveState activeState;
> >
> > -     std::array<IPAFrameContext, kMaxFrameContexts> frameContexts;
> > +     FCQueue<IPAFrameContext> frameContexts;
> >  };
> >
> >  } /* namespace ipa::ipu3 */
> > diff --git a/src/ipa/ipu3/ipu3.cpp b/src/ipa/ipu3/ipu3.cpp
> > index 2f6bb672f7bb..55e82cd404f4 100644
> > --- a/src/ipa/ipu3/ipu3.cpp
> > +++ b/src/ipa/ipu3/ipu3.cpp
> > @@ -38,6 +38,8 @@
> >  #include "algorithms/tone_mapping.h"
> >  #include "libipa/camera_sensor_helper.h"
> >
> > +#include "ipa_context.h"
> > +
> >  /* Minimum grid width, expressed as a number of cells */
> >  static constexpr uint32_t kMinGridWidth = 16;
> >  /* Maximum grid width, expressed as a number of cells */
> > @@ -456,8 +458,7 @@ int IPAIPU3::configure(const IPAConfigInfo &configInfo,
> >
> >       /* Clean IPAActiveState at each reconfiguration. */
> >       context_.activeState = {};
> > -     IPAFrameContext initFrameContext;
> > -     context_.frameContexts.fill(initFrameContext);
> > +     context_.frameContexts.clear();
> >
> >       if (!validateSensorControls()) {
> >               LOG(IPAIPU3, Error) << "Sensor control validation failed.";
> > @@ -569,7 +570,7 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
> >       const ipu3_uapi_stats_3a *stats =
> >               reinterpret_cast<ipu3_uapi_stats_3a *>(mem.data());
> >
> > -     IPAFrameContext &frameContext = context_.frameContexts[frame % kMaxFrameContexts];
> > +     IPAFrameContext &frameContext = context_.frameContexts.get(frame);
> >
> >       if (frameContext.frame != frame)
> >               LOG(IPAIPU3, Warning) << "Frame " << frame << " does not match its frame context";
> > @@ -618,7 +619,11 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
> >  void IPAIPU3::queueRequest(const uint32_t frame, const ControlList &controls)
> >  {
> >       /* \todo Start processing for 'frame' based on 'controls'. */
> > -     context_.frameContexts[frame % kMaxFrameContexts] = { frame, controls };
> > +     IPAFrameContext &frameContext = context_.frameContexts.initialise(frame);
> > +
> > +     /* \todo Implement queueRequest to each algorithm. */
> > +     (void)frameContext;
> > +     (void)controls;
> 
> I'm sure this will be expanded later but it could be simplified as
> 
>  void IPAIPU3::queueRequest(const uint32_t frame, [[maybe_unused]] const ControlList &controls)
>  {
>         /* \todo Start processing for 'frame' based on 'controls'. */
>         context_.frameContexts.initialise(frame);

Yes, but I don't want to make add the maybe_unused's just to remove
them.

And The frame context will be used by the last patch in this series.

If you insist, we can simplify here, but it's just churn eitherway, on
the way to get to the last patch.


>  }
> 
> >  }
> >
> >  /**
> > diff --git a/src/ipa/libipa/fc_queue.cpp b/src/ipa/libipa/fc_queue.cpp
> > new file mode 100644
> > index 000000000000..ecb47f287350
> > --- /dev/null
> > +++ b/src/ipa/libipa/fc_queue.cpp
> > @@ -0,0 +1,96 @@
> > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > +/*
> > + * Copyright (C) 2022, Google Inc.
> > + *
> > + * fc_queue.cpp - IPA Frame context queue
> > + */
> > +
> > +#include "fc_queue.h"
> > +
> > +#include <libcamera/base/log.h>
> > +
> > +namespace libcamera {
> > +
> > +LOG_DEFINE_CATEGORY(FCQueue)
> 
> Is this needed here or can be moved to the .h ?

This is the definition, that has to be in a .cpp doesn't it ?

It's also 'private' to the fc_queue. I wouldn't expect other components
to use this log category.

> 
> > +
> > +namespace ipa {
> > +
> > +/**
> > + * \file fc_queue.h
> > + * \brief Queue to access per-frame Context
> > + */
> > +
> > +/**
> > + * \class FCQueue
> > + * \brief A support class for queueing Frame Context instances through the IPA
> 
> frame context or FrameContext, here and in the other parts of the
> documentation ?

I prefer capitalizing the component names, so that it's clear that we're
talking about a 'libcamera noun'.

In the instance above, I could remove the space..
 (s/Frame Context/FrameContext)

> 
> > + * \tparam FrameContext The IPA specific Frame Context type for this queue
> > + *
> > + * The Frame Context Queue provides a simple circular buffer implementation to
> > + * store IPA specific context for each frame through its lifetime within the
> > + * IPA.
> > + *
> > + * FrameContexts are expected to be referenced by a monotonically increasing
> > + * sequence count referring to a Frame sequence.
>                                    "Frame sequence number"  ?

Ack.


> > + *
> > + * A FrameContext is initialised for a given frame when the corresponding
> > + * Request is first queued into the IPA. From that point on the FrameContext can
> > + * be obtained by the IPA and its algorithms by referencing it from the frame
> > + * sequence number.
> > + *
> > + * A frame sequence number from the image source must correspond to the request
> > + * sequence number for this implementation to be supported in an IPA. It is
> > + * expected that the same sequence number will be used to reference the context
> > + * of the Frame from the point of queueing the request, specifying controls for
> > + * a given frame, and processing of any ISP related controls and statistics for
> > + * the same corresponding image.
> > + *
> > + * IPA specific FrameContexts should inherit from the IPAFrameContext to support
> 
> IPA specific frame context implementations shall inherit from the
> IPAFrameContext base class to support..
> 
> > + * the minimum required features for a FrameContext, including the frame number
> > + * and error flags that relate to the frame.
> > + *
> > + * FrameContexts are overwritten when they are recycled and re-initialised by
> > + * the first access made on them by either initialise(frame) or get(frame). If a
> 
> That's what a circular array does.
> 
> I would rather express the fact that the number of available contexts
> is required to be larger than the platform pipeline depth (with a
> \todo to reference the property once we have it defined). After
> pipelineDepth frames have been processed the FrameContext is recycled
> and forever lost.

The important part to me here is to describe the behaviour of overflow
indeed.

> > + * FrameContext is first accessed through get(frame) before calling initialise()
> > + * a PFCError is automatically raised on the FrameContext to be transferred to
> > + * the Request when it completes.
> 
> This would happen because we have a request underrun, right ?
> 
> I would state that. Like:
> 
> In the case an application does not queue requests to the Camera fast
> enough, frames can be produced and processed by the IPA without a
> corresponding Request being queued. In this case the IPA algorithm
> will try to access the FrameContext with a call to get() before it
> had been initialized at queueRequest() time. In this case there
> is now way the controls associated with the late Request could be
> applied in time, as the frame as already been processed by the IPA,
> the PFCError flag is automatically raised on the FrameContext.
> 
> How does it sound ?

I'll try to respin it all into an updated v2.


> 
> > + */
> > +
> > +/**
> > + * \fn FCQueue::clear()
> > + * \brief Reinitialise all data on the queue
> 
> Or "Clear the queue content" ?

Sure.

> 
> > + *
> > + * Reset the queue and ensure all FrameContext slots are re-initialised.
> 
> I would add that the Queue has to be re-initialized at every streaming
> session start, likely in IPA::configure()

Yes, but actually IPA::start() is the real key point to ensure the queue
is clear. configure() should be irrelevant in fact. 

Except I fear start() may race with queueReqeust(), so I'll have to
verify this. In which case, configure() and stop() would be an
alternative.


> > + */
> > +
> > +/**
> > + * \fn FCQueue::initialise(uint32_t frame)
> > + * \brief Initialize and return the Frame Context at slot specified by \a frame
> > + * \param[in] frame The frame context sequence number
> > + *
> > + * The first call to obtain a FrameContext from the FCQueue should be handled
> > + * through this call. The FrameContext will be initialised for the frame and
> > + * returned to the caller if it was not already initialised.
> > + *
> > + * If the FrameContext was already initialized for this sequence, a warning will
> > + * be reported and the previously initialized FrameContext is returned.
> > + *
> 
> Should we say it is expected to be called at queueRequest() time ?

Yes, probably.

> 
> > + * \return A reference to the FrameContext for sequence \a frame
> > + */
> > +
> > +/**
> > + * \fn FCQueue::get()
> > + * \brief Obtain the Frame Context at slot specified by \a frame
> > + * \param[in] frame The frame context sequence number
> > + *
> > + * Obtains an existing FrameContext from the queue and returns it to the caller.
> > + *
> > + * If the FrameContext is not correctly intiialised for the \a frame, it will be
> 
> s/intiialised/initialised/
> 
> > + * initialised and a PFCError will be flagged on the context to be transferred
> > + * to the Request when it completes.
> > + *
> > + * \return A reference to the FrameContext for sequence \a frame
> > + */
> > +
> > +} /* namespace ipa */
> > +
> > +} /* namespace libcamera */
> > diff --git a/src/ipa/libipa/fc_queue.h b/src/ipa/libipa/fc_queue.h
> > new file mode 100644
> > index 000000000000..82ce36811926
> > --- /dev/null
> > +++ b/src/ipa/libipa/fc_queue.h
> > @@ -0,0 +1,93 @@
> > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > +/*
> > + * Copyright (C) 2022, Google Inc.
> > + *
> > + * fc_queue.h - IPA Frame context queue
> > + *
> 
> Unecessary empty line
> 
> > + */
> > +
> > +#pragma once
> > +
> > +#include <array>
> > +
> > +#include <libcamera/base/log.h>
> > +
> > +#include <libcamera/controls.h>
> 
> Not needed it seems
> 
> > +
> > +namespace libcamera {
> > +
> > +LOG_DECLARE_CATEGORY(FCQueue)
> > +
> > +namespace ipa {
> > +
> > +/*
> > + * Maximum number of frame contexts to be held onto
> > + *
> > + * \todo Should be larger than ISP delay + sensor delay
> > + */
> > +static constexpr uint32_t kMaxFrameContexts = 16;
> > +
> > +template<typename FrameContext>
> > +class FCQueue : public std::array<FrameContext, kMaxFrameContexts>
> > +{
> > +private:
> > +     void initialise(FrameContext &frameContext, const uint32_t frame)
> > +     {
> > +             frameContext = {};
> > +             frameContext.frame = frame;
> > +     }
> > +
> > +public:
> > +     void clear()
> > +     {
> > +             this->fill({});
> > +     }
> > +
> > +     FrameContext &initialise(const uint32_t frame)
> > +     {
> > +             FrameContext &frameContext = this->at(frame & kMaxFrameContexts);
> > +
> > +             /*
> > +              * Do not re-initialise if a get() call has already fetched this
> > +              * frame context to preseve the error flags already raised.
> > +              */
> > +             if (frame == frameContext.frame && frame != 0) {
> 
> This should be <= as it needs to catch cases where the frame context
> has been possibile overwritten by algorithms calling get() for a
> number of times larger than the pipeline depth.

Yes!

I was working on the theory that the PFCError flag would already be
raised by the get() call, but if we overflow even the internal storage
here, I wonder if we should also explicitly set the PFCError here again
as well.



> 
> > +                     LOG(FCQueue, Warning)
> > +                             << "Frame " << frame << " already initialised";
> > +             } else {
> > +                     initialise(frameContext, frame);
> > +             }
> 
> No brances needed it seems
> 
> > +
> > +             return frameContext;
> > +     }
> > +
> > +     FrameContext &get(uint32_t frame)
> > +     {
> > +             FrameContext &frameContext = this->at(frame & kMaxFrameContexts);
> > +
> > +             if (frame != frameContext.frame) {
> 
> Or              if (frame == frameContext.frame)
>                         return frameContext;
> 
> To save one indentation level. Up to you.

Oh yes, definitely ;-)



> 
> > +                     LOG(FCQueue, Warning)
> > +                             << "Obtained an uninitialised FrameContext for "
> > +                             << frame;
> > +
> > +                     initialise(frameContext, frame);
> > +
> > +                     /*
> > +                      * The frame context has been retrieved before it was
> > +                      * initialised through the initialise() call. This
> > +                      * indicates an algorithm attempted to access a Frame
> > +                      * context before it was queued to the IPA.
> > +                      *
> > +                      * Controls applied for this request may be left
> > +                      * unhandled.
> > +                      */
> > +                     frameContext.error |= Request::PFCError;
> > +             }
> > +
> > +             return frameContext;
> > +     }
> > +};
> > +
> > +} /* namespace ipa */
> > +
> > +} /* namespace libcamera */
> > diff --git a/src/ipa/libipa/meson.build b/src/ipa/libipa/meson.build
> > index fb894bc614af..016b8e0ec9be 100644
> > --- a/src/ipa/libipa/meson.build
> > +++ b/src/ipa/libipa/meson.build
> > @@ -3,6 +3,7 @@
> >  libipa_headers = files([
> >      'algorithm.h',
> >      'camera_sensor_helper.h',
> > +    'fc_queue.h',
> >      'histogram.h',
> >      'module.h',
> >  ])
> > @@ -10,6 +11,7 @@ libipa_headers = files([
> >  libipa_sources = files([
> >      'algorithm.cpp',
> >      'camera_sensor_helper.cpp',
> > +    'fc_queue.cpp',
> >      'histogram.cpp',
> >      'module.cpp',
> >  ])
> > --
> > 2.34.1
> >

Quoting Kieran Bingham (2022-07-26 11:00:03)
> Quoting Jacopo Mondi (2022-07-25 16:20:51)
> > Hi Kieran
> > 
> > On Thu, Jul 21, 2022 at 01:13:02PM +0100, Kieran Bingham via libcamera-devel wrote:
> > > From: Umang Jain <umang.jain@ideasonboard.com>
> > >
> > > Provide a direct FCQueue abstraction to facilitate creating a queue of
> > > Frame Context structures.
> > >
> > > The IPAFrameContext is moved back to the ipu3/ipa_context.h and a queue
> > > added to the IPU3, but the Algorithms are not yet moved from the single
> > > FrameContext exposed by the IPA context to use the correct one from the
> > > queue until the Algorithm interfaces are fully updated.
> > >
> > > Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
> > > Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> > > ---
> > >  src/ipa/ipu3/ipa_context.cpp | 17 -------
> > >  src/ipa/ipu3/ipa_context.h   | 15 ++----
> > >  src/ipa/ipu3/ipu3.cpp        | 13 +++--
> > >  src/ipa/libipa/fc_queue.cpp  | 96 ++++++++++++++++++++++++++++++++++++
> > >  src/ipa/libipa/fc_queue.h    | 93 ++++++++++++++++++++++++++++++++++
> > >  src/ipa/libipa/meson.build   |  2 +
> > >  6 files changed, 204 insertions(+), 32 deletions(-)
> > >  create mode 100644 src/ipa/libipa/fc_queue.cpp
> > >  create mode 100644 src/ipa/libipa/fc_queue.h
> > >
> > > diff --git a/src/ipa/ipu3/ipa_context.cpp b/src/ipa/ipu3/ipa_context.cpp
> > > index 13cdb835ef7f..dd139cb4c868 100644
> > > --- a/src/ipa/ipu3/ipa_context.cpp
> > > +++ b/src/ipa/ipu3/ipa_context.cpp
> > > @@ -180,27 +180,10 @@ namespace libcamera::ipa::ipu3 {
> > >   * <linux/intel-ipu3.h> struct ipu3_uapi_gamma_corr_lut for further details.
> > >   */
> > >
> > > -/**
> > > - * \brief Default constructor for IPAFrameContext
> > > - */
> > > -IPAFrameContext::IPAFrameContext() = default;
> > > -
> > > -/**
> > > - * \brief Construct a IPAFrameContext instance
> > > - */
> > > -IPAFrameContext::IPAFrameContext(uint32_t id, const ControlList &reqControls)
> > > -     : frame(id), frameControls(reqControls)
> > > -{
> > > -     sensor = {};
> > > -}
> > > -
> > >  /**
> > >   * \var IPAFrameContext::frame
> > >   * \brief The frame number
> > >   *
> > > - * \var IPAFrameContext::frameControls
> > > - * \brief Controls sent in by the application while queuing the request
> > > - *
> > >   * \var IPAFrameContext::sensor
> > >   * \brief Effective sensor values that were applied for the frame
> > >   *
> > > diff --git a/src/ipa/ipu3/ipa_context.h b/src/ipa/ipu3/ipa_context.h
> > > index 42e11141d3a1..193fc44a821a 100644
> > > --- a/src/ipa/ipu3/ipa_context.h
> > > +++ b/src/ipa/ipu3/ipa_context.h
> > > @@ -8,8 +8,6 @@
> > >
> > >  #pragma once
> > >
> > > -#include <array>
> > > -
> > >  #include <linux/intel-ipu3.h>
> > >
> > >  #include <libcamera/base/utils.h>
> > > @@ -17,13 +15,12 @@
> > >  #include <libcamera/controls.h>
> > >  #include <libcamera/geometry.h>
> > >
> > > +#include <libipa/fc_queue.h>
> > > +
> > >  namespace libcamera {
> > >
> > >  namespace ipa::ipu3 {
> > >
> > > -/* Maximum number of frame contexts to be held */
> > > -static constexpr uint32_t kMaxFrameContexts = 16;
> > 
> > The size of the FCQueue should probably come from the IPA
> > implementation, as different platforms will have a different queue
> > depth to handle.
> > 
> > It can be made a second template argument.
> 
> Yes, this is absoultely a platform specific value.
> 
> I simply haven't made it adjustable yet.
> 
> I believe it could also be handled on top, as '16' is bigger than both
> expected platforms currently ;-)
> 
> I'd rather handle that as a separate patch as well - as whatever size it
> is contstructed as needs to be conveyed to the pipeline handler too.
> 
> Either the PH should state what size the IPA should make, or otherwise
> they should both be hardcoded to the same size.
> 
> But that's enough discussion that I think it deserves it's own
> patch/implementation.
> 
> 
> > > -
> > >  struct IPASessionConfiguration {
> > >       struct {
> > >               ipu3_uapi_grid_config bdsGrid;
> > > @@ -77,23 +74,19 @@ struct IPAActiveState {
> > >  };
> > >
> > >  struct IPAFrameContext {
> > > -     IPAFrameContext();
> > > -     IPAFrameContext(uint32_t id, const ControlList &reqControls);
> > > +     uint32_t frame;
> > >
> > >       struct {
> > >               uint32_t exposure;
> > >               double gain;
> > >       } sensor;
> > > -
> > > -     uint32_t frame;
> > > -     ControlList frameControls;
> > >  };
> > >
> > >  struct IPAContext {
> > >       IPASessionConfiguration configuration;
> > >       IPAActiveState activeState;
> > >
> > > -     std::array<IPAFrameContext, kMaxFrameContexts> frameContexts;
> > > +     FCQueue<IPAFrameContext> frameContexts;
> > >  };
> > >
> > >  } /* namespace ipa::ipu3 */
> > > diff --git a/src/ipa/ipu3/ipu3.cpp b/src/ipa/ipu3/ipu3.cpp
> > > index 2f6bb672f7bb..55e82cd404f4 100644
> > > --- a/src/ipa/ipu3/ipu3.cpp
> > > +++ b/src/ipa/ipu3/ipu3.cpp
> > > @@ -38,6 +38,8 @@
> > >  #include "algorithms/tone_mapping.h"
> > >  #include "libipa/camera_sensor_helper.h"
> > >
> > > +#include "ipa_context.h"
> > > +
> > >  /* Minimum grid width, expressed as a number of cells */
> > >  static constexpr uint32_t kMinGridWidth = 16;
> > >  /* Maximum grid width, expressed as a number of cells */
> > > @@ -456,8 +458,7 @@ int IPAIPU3::configure(const IPAConfigInfo &configInfo,
> > >
> > >       /* Clean IPAActiveState at each reconfiguration. */
> > >       context_.activeState = {};
> > > -     IPAFrameContext initFrameContext;
> > > -     context_.frameContexts.fill(initFrameContext);
> > > +     context_.frameContexts.clear();
> > >
> > >       if (!validateSensorControls()) {
> > >               LOG(IPAIPU3, Error) << "Sensor control validation failed.";
> > > @@ -569,7 +570,7 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
> > >       const ipu3_uapi_stats_3a *stats =
> > >               reinterpret_cast<ipu3_uapi_stats_3a *>(mem.data());
> > >
> > > -     IPAFrameContext &frameContext = context_.frameContexts[frame % kMaxFrameContexts];
> > > +     IPAFrameContext &frameContext = context_.frameContexts.get(frame);
> > >
> > >       if (frameContext.frame != frame)
> > >               LOG(IPAIPU3, Warning) << "Frame " << frame << " does not match its frame context";
> > > @@ -618,7 +619,11 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
> > >  void IPAIPU3::queueRequest(const uint32_t frame, const ControlList &controls)
> > >  {
> > >       /* \todo Start processing for 'frame' based on 'controls'. */
> > > -     context_.frameContexts[frame % kMaxFrameContexts] = { frame, controls };
> > > +     IPAFrameContext &frameContext = context_.frameContexts.initialise(frame);
> > > +
> > > +     /* \todo Implement queueRequest to each algorithm. */
> > > +     (void)frameContext;
> > > +     (void)controls;
> > 
> > I'm sure this will be expanded later but it could be simplified as
> > 
> >  void IPAIPU3::queueRequest(const uint32_t frame, [[maybe_unused]] const ControlList &controls)
> >  {
> >         /* \todo Start processing for 'frame' based on 'controls'. */
> >         context_.frameContexts.initialise(frame);
> 
> Yes, but I don't want to make add the maybe_unused's just to remove
> them.
> 
> And The frame context will be used by the last patch in this series.
> 
> If you insist, we can simplify here, but it's just churn eitherway, on
> the way to get to the last patch.
> 
> 
> >  }
> > 
> > >  }
> > >
> > >  /**
> > > diff --git a/src/ipa/libipa/fc_queue.cpp b/src/ipa/libipa/fc_queue.cpp
> > > new file mode 100644
> > > index 000000000000..ecb47f287350
> > > --- /dev/null
> > > +++ b/src/ipa/libipa/fc_queue.cpp
> > > @@ -0,0 +1,96 @@
> > > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > > +/*
> > > + * Copyright (C) 2022, Google Inc.
> > > + *
> > > + * fc_queue.cpp - IPA Frame context queue
> > > + */
> > > +
> > > +#include "fc_queue.h"
> > > +
> > > +#include <libcamera/base/log.h>
> > > +
> > > +namespace libcamera {
> > > +
> > > +LOG_DEFINE_CATEGORY(FCQueue)
> > 
> > Is this needed here or can be moved to the .h ?
> 
> This is the definition, that has to be in a .cpp doesn't it ?
> 
> It's also 'private' to the fc_queue. I wouldn't expect other components
> to use this log category.
> 
> > 
> > > +
> > > +namespace ipa {
> > > +
> > > +/**
> > > + * \file fc_queue.h
> > > + * \brief Queue to access per-frame Context
> > > + */
> > > +
> > > +/**
> > > + * \class FCQueue
> > > + * \brief A support class for queueing Frame Context instances through the IPA
> > 
> > frame context or FrameContext, here and in the other parts of the
> > documentation ?
> 
> I prefer capitalizing the component names, so that it's clear that we're
> talking about a 'libcamera noun'.
> 
> In the instance above, I could remove the space..
>  (s/Frame Context/FrameContext)
> 
> > 
> > > + * \tparam FrameContext The IPA specific Frame Context type for this queue
> > > + *
> > > + * The Frame Context Queue provides a simple circular buffer implementation to
> > > + * store IPA specific context for each frame through its lifetime within the
> > > + * IPA.
> > > + *
> > > + * FrameContexts are expected to be referenced by a monotonically increasing
> > > + * sequence count referring to a Frame sequence.
> >                                    "Frame sequence number"  ?
> 
> Ack.
> 
> 
> > > + *
> > > + * A FrameContext is initialised for a given frame when the corresponding
> > > + * Request is first queued into the IPA. From that point on the FrameContext can
> > > + * be obtained by the IPA and its algorithms by referencing it from the frame
> > > + * sequence number.
> > > + *
> > > + * A frame sequence number from the image source must correspond to the request
> > > + * sequence number for this implementation to be supported in an IPA. It is
> > > + * expected that the same sequence number will be used to reference the context
> > > + * of the Frame from the point of queueing the request, specifying controls for
> > > + * a given frame, and processing of any ISP related controls and statistics for
> > > + * the same corresponding image.
> > > + *
> > > + * IPA specific FrameContexts should inherit from the IPAFrameContext to support
> > 
> > IPA specific frame context implementations shall inherit from the
> > IPAFrameContext base class to support..
> > 
> > > + * the minimum required features for a FrameContext, including the frame number
> > > + * and error flags that relate to the frame.
> > > + *
> > > + * FrameContexts are overwritten when they are recycled and re-initialised by
> > > + * the first access made on them by either initialise(frame) or get(frame). If a
> > 
> > That's what a circular array does.
> > 
> > I would rather express the fact that the number of available contexts
> > is required to be larger than the platform pipeline depth (with a
> > \todo to reference the property once we have it defined). After
> > pipelineDepth frames have been processed the FrameContext is recycled
> > and forever lost.
> 
> The important part to me here is to describe the behaviour of overflow
> indeed.
> 
> > > + * FrameContext is first accessed through get(frame) before calling initialise()
> > > + * a PFCError is automatically raised on the FrameContext to be transferred to
> > > + * the Request when it completes.
> > 
> > This would happen because we have a request underrun, right ?
> > 
> > I would state that. Like:
> > 
> > In the case an application does not queue requests to the Camera fast
> > enough, frames can be produced and processed by the IPA without a
> > corresponding Request being queued. In this case the IPA algorithm
> > will try to access the FrameContext with a call to get() before it
> > had been initialized at queueRequest() time. In this case there
> > is now way the controls associated with the late Request could be
> > applied in time, as the frame as already been processed by the IPA,
> > the PFCError flag is automatically raised on the FrameContext.
> > 
> > How does it sound ?
> 
> I'll try to respin it all into an updated v2.
> 
> 
> > 
> > > + */
> > > +
> > > +/**
> > > + * \fn FCQueue::clear()
> > > + * \brief Reinitialise all data on the queue
> > 
> > Or "Clear the queue content" ?
> 
> Sure.
> 
> > 
> > > + *
> > > + * Reset the queue and ensure all FrameContext slots are re-initialised.
> > 
> > I would add that the Queue has to be re-initialized at every streaming
> > session start, likely in IPA::configure()
> 
> Yes, but actually IPA::start() is the real key point to ensure the queue
> is clear. configure() should be irrelevant in fact. 
> 
> Except I fear start() may race with queueReqeust(), so I'll have to
> verify this. In which case, configure() and stop() would be an
> alternative.
> 
> 
> > > + */
> > > +
> > > +/**
> > > + * \fn FCQueue::initialise(uint32_t frame)
> > > + * \brief Initialize and return the Frame Context at slot specified by \a frame
> > > + * \param[in] frame The frame context sequence number
> > > + *
> > > + * The first call to obtain a FrameContext from the FCQueue should be handled
> > > + * through this call. The FrameContext will be initialised for the frame and
> > > + * returned to the caller if it was not already initialised.
> > > + *
> > > + * If the FrameContext was already initialized for this sequence, a warning will
> > > + * be reported and the previously initialized FrameContext is returned.
> > > + *
> > 
> > Should we say it is expected to be called at queueRequest() time ?
> 
> Yes, probably.
> 
> > 
> > > + * \return A reference to the FrameContext for sequence \a frame
> > > + */
> > > +
> > > +/**
> > > + * \fn FCQueue::get()
> > > + * \brief Obtain the Frame Context at slot specified by \a frame
> > > + * \param[in] frame The frame context sequence number
> > > + *
> > > + * Obtains an existing FrameContext from the queue and returns it to the caller.
> > > + *
> > > + * If the FrameContext is not correctly intiialised for the \a frame, it will be
> > 
> > s/intiialised/initialised/
> > 
> > > + * initialised and a PFCError will be flagged on the context to be transferred
> > > + * to the Request when it completes.
> > > + *
> > > + * \return A reference to the FrameContext for sequence \a frame
> > > + */
> > > +
> > > +} /* namespace ipa */
> > > +
> > > +} /* namespace libcamera */
> > > diff --git a/src/ipa/libipa/fc_queue.h b/src/ipa/libipa/fc_queue.h
> > > new file mode 100644
> > > index 000000000000..82ce36811926
> > > --- /dev/null
> > > +++ b/src/ipa/libipa/fc_queue.h
> > > @@ -0,0 +1,93 @@
> > > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > > +/*
> > > + * Copyright (C) 2022, Google Inc.
> > > + *
> > > + * fc_queue.h - IPA Frame context queue
> > > + *
> > 
> > Unecessary empty line
> > 
> > > + */
> > > +
> > > +#pragma once
> > > +
> > > +#include <array>
> > > +
> > > +#include <libcamera/base/log.h>
> > > +
> > > +#include <libcamera/controls.h>
> > 
> > Not needed it seems
> > 
> > > +
> > > +namespace libcamera {
> > > +
> > > +LOG_DECLARE_CATEGORY(FCQueue)
> > > +
> > > +namespace ipa {
> > > +
> > > +/*
> > > + * Maximum number of frame contexts to be held onto
> > > + *
> > > + * \todo Should be larger than ISP delay + sensor delay
> > > + */
> > > +static constexpr uint32_t kMaxFrameContexts = 16;
> > > +
> > > +template<typename FrameContext>
> > > +class FCQueue : public std::array<FrameContext, kMaxFrameContexts>
> > > +{
> > > +private:
> > > +     void initialise(FrameContext &frameContext, const uint32_t frame)
> > > +     {
> > > +             frameContext = {};
> > > +             frameContext.frame = frame;
> > > +     }
> > > +
> > > +public:
> > > +     void clear()
> > > +     {
> > > +             this->fill({});
> > > +     }
> > > +
> > > +     FrameContext &initialise(const uint32_t frame)
> > > +     {
> > > +             FrameContext &frameContext = this->at(frame & kMaxFrameContexts);
> > > +
> > > +             /*
> > > +              * Do not re-initialise if a get() call has already fetched this
> > > +              * frame context to preseve the error flags already raised.
> > > +              */
> > > +             if (frame == frameContext.frame && frame != 0) {
> > 
> > This should be <= as it needs to catch cases where the frame context
> > has been possibile overwritten by algorithms calling get() for a
> > number of times larger than the pipeline depth.
> 
> Yes!
> 
> I was working on the theory that the PFCError flag would already be
> raised by the get() call, but if we overflow even the internal storage
> here, I wonder if we should also explicitly set the PFCError here again
> as well.
> 
> 
> 
> > 
> > > +                     LOG(FCQueue, Warning)
> > > +                             << "Frame " << frame << " already initialised";
> > > +             } else {
> > > +                     initialise(frameContext, frame);
> > > +             }
> > 
> > No brances needed it seems
> > 
> > > +
> > > +             return frameContext;
> > > +     }
> > > +
> > > +     FrameContext &get(uint32_t frame)
> > > +     {
> > > +             FrameContext &frameContext = this->at(frame & kMaxFrameContexts);
> > > +
> > > +             if (frame != frameContext.frame) {
> > 
> > Or              if (frame == frameContext.frame)
> >                         return frameContext;
> > 
> > To save one indentation level. Up to you.
> 
> Oh yes, definitely ;-)
> 
> 



An assertion here might be useful to ensure that get() isn't trying to
initialise over a 'newer' frame.

	ASSERT(frameContext.frame < frame);

If frameContext.frame > frame - then it means something is trying to
access the FCQ while the incoming request queue is overflowing the queue
which I believe we will, but have not yet prevented from happening on 
the Pipeline Handler side.


> 
> > 
> > > +                     LOG(FCQueue, Warning)
> > > +                             << "Obtained an uninitialised FrameContext for "
> > > +                             << frame;
> > > +
> > > +                     initialise(frameContext, frame);
> > > +
> > > +                     /*
> > > +                      * The frame context has been retrieved before it was
> > > +                      * initialised through the initialise() call. This
> > > +                      * indicates an algorithm attempted to access a Frame
> > > +                      * context before it was queued to the IPA.
> > > +                      *
> > > +                      * Controls applied for this request may be left
> > > +                      * unhandled.
> > > +                      */
> > > +                     frameContext.error |= Request::PFCError;
> > > +             }
> > > +
> > > +             return frameContext;
> > > +     }
> > > +};
> > > +
> > > +} /* namespace ipa */
> > > +
> > > +} /* namespace libcamera */
> > > diff --git a/src/ipa/libipa/meson.build b/src/ipa/libipa/meson.build
> > > index fb894bc614af..016b8e0ec9be 100644
> > > --- a/src/ipa/libipa/meson.build
> > > +++ b/src/ipa/libipa/meson.build
> > > @@ -3,6 +3,7 @@
> > >  libipa_headers = files([
> > >      'algorithm.h',
> > >      'camera_sensor_helper.h',
> > > +    'fc_queue.h',
> > >      'histogram.h',
> > >      'module.h',
> > >  ])
> > > @@ -10,6 +11,7 @@ libipa_headers = files([
> > >  libipa_sources = files([
> > >      'algorithm.cpp',
> > >      'camera_sensor_helper.cpp',
> > > +    'fc_queue.cpp',
> > >      'histogram.cpp',
> > >      'module.cpp',
> > >  ])
> > > --
> > > 2.34.1
> > >

Hi Umang,
  I'm applying comments on top of Kierans' RFC and I have two
questions here

On Sat, Jul 23, 2022 at 02:21:48AM +0530, Umang Jain via libcamera-devel wrote:
> Hi Kieran,
>
> On 7/21/22 17:43, Kieran Bingham wrote:
> > From: Umang Jain <umang.jain@ideasonboard.com>
> >
> > Provide a direct FCQueue abstraction to facilitate creating a queue of
> > Frame Context structures.
>
>
> Ah we are back again to have FCQueue separately (in class files) :-)
>
> >
> > The IPAFrameContext is moved back to the ipu3/ipa_context.h and a queue
>
>
> You can just say that the constructors for IPAFrameContext are dropped.
>
>
> > added to the IPU3, but the Algorithms are not yet moved from the single
>
> nit: s/IPU3/IPAIPU3/
>
> Furthermore, a queue is already present in the form of:
>
>         std::array<IPAFrameContext, kMaxFrameContexts> frameContexts;
>
> It is just that the queue is transformed to FCQueue. Since this is a RFC, I
> won't dwell much on the commit message, it can get accurately described in
> future interations.
>
> > FrameContext exposed by the IPA context to use the correct one from the
> > queue until the Algorithm interfaces are fully updated.
> >
> > Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
> > Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> > ---
> >   src/ipa/ipu3/ipa_context.cpp | 17 -------
> >   src/ipa/ipu3/ipa_context.h   | 15 ++----
> >   src/ipa/ipu3/ipu3.cpp        | 13 +++--
> >   src/ipa/libipa/fc_queue.cpp  | 96 ++++++++++++++++++++++++++++++++++++
> >   src/ipa/libipa/fc_queue.h    | 93 ++++++++++++++++++++++++++++++++++
> >   src/ipa/libipa/meson.build   |  2 +
> >   6 files changed, 204 insertions(+), 32 deletions(-)
> >   create mode 100644 src/ipa/libipa/fc_queue.cpp
> >   create mode 100644 src/ipa/libipa/fc_queue.h
> >
> > diff --git a/src/ipa/ipu3/ipa_context.cpp b/src/ipa/ipu3/ipa_context.cpp
> > index 13cdb835ef7f..dd139cb4c868 100644
> > --- a/src/ipa/ipu3/ipa_context.cpp
> > +++ b/src/ipa/ipu3/ipa_context.cpp
> > @@ -180,27 +180,10 @@ namespace libcamera::ipa::ipu3 {
> >    * <linux/intel-ipu3.h> struct ipu3_uapi_gamma_corr_lut for further details.
> >    */
> > -/**
> > - * \brief Default constructor for IPAFrameContext
> > - */
> > -IPAFrameContext::IPAFrameContext() = default;
> > -
> > -/**
> > - * \brief Construct a IPAFrameContext instance
> > - */
> > -IPAFrameContext::IPAFrameContext(uint32_t id, const ControlList &reqControls)
> > -	: frame(id), frameControls(reqControls)
> > -{
> > -	sensor = {};
> > -}
> > -
> >   /**
> >    * \var IPAFrameContext::frame
> >    * \brief The frame number
> >    *
> > - * \var IPAFrameContext::frameControls
> > - * \brief Controls sent in by the application while queuing the request
> > - *
> >    * \var IPAFrameContext::sensor
> >    * \brief Effective sensor values that were applied for the frame
> >    *
> > diff --git a/src/ipa/ipu3/ipa_context.h b/src/ipa/ipu3/ipa_context.h
> > index 42e11141d3a1..193fc44a821a 100644
> > --- a/src/ipa/ipu3/ipa_context.h
> > +++ b/src/ipa/ipu3/ipa_context.h
> > @@ -8,8 +8,6 @@
> >   #pragma once
> > -#include <array>
> > -
> >   #include <linux/intel-ipu3.h>
> >   #include <libcamera/base/utils.h>
> > @@ -17,13 +15,12 @@
> >   #include <libcamera/controls.h>
> >   #include <libcamera/geometry.h>
> > +#include <libipa/fc_queue.h>
> > +
> >   namespace libcamera {
> >   namespace ipa::ipu3 {
> > -/* Maximum number of frame contexts to be held */
> > -static constexpr uint32_t kMaxFrameContexts = 16;
> > -
> >   struct IPASessionConfiguration {
> >   	struct {
> >   		ipu3_uapi_grid_config bdsGrid;
> > @@ -77,23 +74,19 @@ struct IPAActiveState {
> >   };
> >   struct IPAFrameContext {
> > -	IPAFrameContext();
> > -	IPAFrameContext(uint32_t id, const ControlList &reqControls);
> > +	uint32_t frame;
> >   	struct {
> >   		uint32_t exposure;
> >   		double gain;
> >   	} sensor;
> > -
> > -	uint32_t frame;
> > -	ControlList frameControls;
>
>
> Okay, we dropped the ControlList here, because every algo will get the
> ControlList in the new interface
>
> >   };
> >   struct IPAContext {
> >   	IPASessionConfiguration configuration;
> >   	IPAActiveState activeState;
> > -	std::array<IPAFrameContext, kMaxFrameContexts> frameContexts;
> > +	FCQueue<IPAFrameContext> frameContexts;
> >   };
> >   } /* namespace ipa::ipu3 */
> > diff --git a/src/ipa/ipu3/ipu3.cpp b/src/ipa/ipu3/ipu3.cpp
> > index 2f6bb672f7bb..55e82cd404f4 100644
> > --- a/src/ipa/ipu3/ipu3.cpp
> > +++ b/src/ipa/ipu3/ipu3.cpp
> > @@ -38,6 +38,8 @@
> >   #include "algorithms/tone_mapping.h"
> >   #include "libipa/camera_sensor_helper.h"
> > +#include "ipa_context.h"
> > +
> >   /* Minimum grid width, expressed as a number of cells */
> >   static constexpr uint32_t kMinGridWidth = 16;
> >   /* Maximum grid width, expressed as a number of cells */
> > @@ -456,8 +458,7 @@ int IPAIPU3::configure(const IPAConfigInfo &configInfo,
> >   	/* Clean IPAActiveState at each reconfiguration. */
> >   	context_.activeState = {};
> > -	IPAFrameContext initFrameContext;
> > -	context_.frameContexts.fill(initFrameContext);
> > +	context_.frameContexts.clear();
> context_.frameContexts.clear();
>
> Should also be done in IPAIPU3::stop().
>

I understand IPA::configure() is not enough, as we can have star/stop
sequences without a reconfiguration in between.

But why stop() and not start()

> >   	if (!validateSensorControls()) {
> >   		LOG(IPAIPU3, Error) << "Sensor control validation failed.";
> > @@ -569,7 +570,7 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
> >   	const ipu3_uapi_stats_3a *stats =
> >   		reinterpret_cast<ipu3_uapi_stats_3a *>(mem.data());
> > -	IPAFrameContext &frameContext = context_.frameContexts[frame % kMaxFrameContexts];
> > +	IPAFrameContext &frameContext = context_.frameContexts.get(frame);
> >   	if (frameContext.frame != frame)
> >   		LOG(IPAIPU3, Warning) << "Frame " << frame << " does not match its frame context";
> > @@ -618,7 +619,11 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
> >   void IPAIPU3::queueRequest(const uint32_t frame, const ControlList &controls)
> >   {
> >   	/* \todo Start processing for 'frame' based on 'controls'. */
> > -	context_.frameContexts[frame % kMaxFrameContexts] = { frame, controls };
> > +	IPAFrameContext &frameContext = context_.frameContexts.initialise(frame);
> > +
> > +	/* \todo Implement queueRequest to each algorithm. */
> > +	(void)frameContext;
> > +	(void)controls;
> >   }
> >   /**
> > diff --git a/src/ipa/libipa/fc_queue.cpp b/src/ipa/libipa/fc_queue.cpp
> > new file mode 100644
> > index 000000000000..ecb47f287350
> > --- /dev/null
> > +++ b/src/ipa/libipa/fc_queue.cpp
> > @@ -0,0 +1,96 @@
> > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > +/*
> > + * Copyright (C) 2022, Google Inc.
> > + *
> > + * fc_queue.cpp - IPA Frame context queue
> > + */
> > +
> > +#include "fc_queue.h"
> > +
> > +#include <libcamera/base/log.h>
> > +
> > +namespace libcamera {
> > +
> > +LOG_DEFINE_CATEGORY(FCQueue)
> > +
> > +namespace ipa {
> > +
> > +/**
> > + * \file fc_queue.h
> > + * \brief Queue to access per-frame Context
> > + */
> > +
> > +/**
> > + * \class FCQueue
> > + * \brief A support class for queueing Frame Context instances through the IPA
>
>
> s/queueing/queuing/
>

Both spelling seems to be correct, and we have both in the codebase.
I'll keep what Kieran had initially.

Thanks
  j

> > + * \tparam FrameContext The IPA specific Frame Context type for this queue
> > + *
> > + * The Frame Context Queue provides a simple circular buffer implementation to
> > + * store IPA specific context for each frame through its lifetime within the
> > + * IPA.
> > + *
> > + * FrameContexts are expected to be referenced by a monotonically increasing
> > + * sequence count referring to a Frame sequence.
> > + *
> > + * A FrameContext is initialised for a given frame when the corresponding
> > + * Request is first queued into the IPA. From that point on the FrameContext can
> > + * be obtained by the IPA and its algorithms by referencing it from the frame
> > + * sequence number.
> > + *
> > + * A frame sequence number from the image source must correspond to the request
> > + * sequence number for this implementation to be supported in an IPA. It is
> > + * expected that the same sequence number will be used to reference the context
> > + * of the Frame from the point of queueing the request, specifying controls for
>
>
> s/queueing/queuing/
>
> > + * a given frame, and processing of any ISP related controls and statistics for
> > + * the same corresponding image.
> > + *
> > + * IPA specific FrameContexts should inherit from the IPAFrameContext to support
> > + * the minimum required features for a FrameContext, including the frame number
> > + * and error flags that relate to the frame.
> > + *
> > + * FrameContexts are overwritten when they are recycled and re-initialised by
> > + * the first access made on them by either initialise(frame) or get(frame). If a
> > + * FrameContext is first accessed through get(frame) before calling initialise()
> > + * a PFCError is automatically raised on the FrameContext to be transferred to
> > + * the Request when it completes.
>
>
> I get the point here, but I feel the documentation on get()/PFCError etc. is
> a bit jerky.
>
> Once we have some context setup for FCQ, goals, error situations etc. maybe
> it will fit into the flow.
>
> > + */
> > +
> > +/**
> > + * \fn FCQueue::clear()
> > + * \brief Reinitialise all data on the queue
> > + *
> > + * Reset the queue and ensure all FrameContext slots are re-initialised.
> > + */
> > +
> > +/**
> > + * \fn FCQueue::initialise(uint32_t frame)
> > + * \brief Initialize and return the Frame Context at slot specified by \a frame
> > + * \param[in] frame The frame context sequence number
> > + *
> > + * The first call to obtain a FrameContext from the FCQueue should be handled
> > + * through this call. The FrameContext will be initialised for the frame and
> > + * returned to the caller if it was not already initialised.
> > + *
> > + * If the FrameContext was already initialized for this sequence, a warning will
> > + * be reported and the previously initialized FrameContext is returned.
> > + *
> > + * \return A reference to the FrameContext for sequence \a frame
> > + */
> > +
> > +/**
> > + * \fn FCQueue::get()
> > + * \brief Obtain the Frame Context at slot specified by \a frame
> > + * \param[in] frame The frame context sequence number
> > + *
> > + * Obtains an existing FrameContext from the queue and returns it to the caller.
> > + *
> > + * If the FrameContext is not correctly intiialised for the \a frame, it will be
> s/intiialised/initialised/
> > + * initialised and a PFCError will be flagged on the context to be transferred
> > + * to the Request when it completes.
> > + *
> > + * \return A reference to the FrameContext for sequence \a frame
> > + */
> > +
> > +} /* namespace ipa */
> > +
> > +} /* namespace libcamera */
> > diff --git a/src/ipa/libipa/fc_queue.h b/src/ipa/libipa/fc_queue.h
> > new file mode 100644
> > index 000000000000..82ce36811926
> > --- /dev/null
> > +++ b/src/ipa/libipa/fc_queue.h
> > @@ -0,0 +1,93 @@
> > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > +/*
> > + * Copyright (C) 2022, Google Inc.
> > + *
> > + * fc_queue.h - IPA Frame context queue
> > + *
> > + */
> > +
> > +#pragma once
> > +
> > +#include <array>
> > +
> > +#include <libcamera/base/log.h>
> > +
> > +#include <libcamera/controls.h>
> > +
> > +namespace libcamera {
> > +
> > +LOG_DECLARE_CATEGORY(FCQueue)
> > +
> > +namespace ipa {
> > +
> > +/*
> > + * Maximum number of frame contexts to be held onto
> > + *
> > + * \todo Should be larger than ISP delay + sensor delay
> > + */
> > +static constexpr uint32_t kMaxFrameContexts = 16;
> > +
> > +template<typename FrameContext>
>
> Nice, templates wohoo!
>
> > +class FCQueue : public std::array<FrameContext, kMaxFrameContexts>
>
>
> Private inheritance will be required. We don't want to expose std::array
> APIs to get used accidentally.
>
> > +{
> > +private:
> > +	void initialise(FrameContext &frameContext, const uint32_t frame)
> > +	{
> > +		frameContext = {};
> > +		frameContext.frame = frame;
> > +	}
> > +
> > +public:
> > +	void clear()
> > +	{
> > +		this->fill({});
> > +	}
> > +
> > +	FrameContext &initialise(const uint32_t frame)
> > +	{
> > +		FrameContext &frameContext = this->at(frame & kMaxFrameContexts);
> > +
> > +		/*
> > +		 * Do not re-initialise if a get() call has already fetched this
> > +		 * frame context to preseve the error flags already raised.
> > +		 */
> > +		if (frame == frameContext.frame && frame != 0) {
> > +			LOG(FCQueue, Warning)
> > +				<< "Frame " << frame << " already initialised";
> > +		} else {
> > +			initialise(frameContext, frame);
> > +		}
> > +
> > +		return frameContext;
> > +	}
> > +
> > +	FrameContext &get(uint32_t frame)
> > +	{
> > +		FrameContext &frameContext = this->at(frame & kMaxFrameContexts);
> > +
> > +		if (frame != frameContext.frame) {
> > +			LOG(FCQueue, Warning)
> > +				<< "Obtained an uninitialised FrameContext for "
> > +				<< frame;
> > +
> > +			initialise(frameContext, frame);
> > +
> > +			/*
> > +			 * The frame context has been retrieved before it was
> > +			 * initialised through the initialise() call. This
> > +			 * indicates an algorithm attempted to access a Frame
> > +			 * context before it was queued to the IPA.
> > +			 *
> > +			 * Controls applied for this request may be left
> > +			 * unhandled.
> > +			 */
> > +			frameContext.error |= Request::PFCError;
> > +		}
> > +
> > +		return frameContext;
> > +	}
> > +};
>
>
> For now, it looks more or less as per stated in the design.
>
> Thank you for the work!
>
> > +
> > +} /* namespace ipa */
> > +
> > +} /* namespace libcamera */
> > diff --git a/src/ipa/libipa/meson.build b/src/ipa/libipa/meson.build
> > index fb894bc614af..016b8e0ec9be 100644
> > --- a/src/ipa/libipa/meson.build
> > +++ b/src/ipa/libipa/meson.build
> > @@ -3,6 +3,7 @@
> >   libipa_headers = files([
> >       'algorithm.h',
> >       'camera_sensor_helper.h',
> > +    'fc_queue.h',
> >       'histogram.h',
> >       'module.h',
> >   ])
> > @@ -10,6 +11,7 @@ libipa_headers = files([
> >   libipa_sources = files([
> >       'algorithm.cpp',
> >       'camera_sensor_helper.cpp',
> > +    'fc_queue.cpp',
> >       'histogram.cpp',
> >       'module.cpp',
> >   ])

On Thu, Aug 04, 2022 at 02:54:37PM +0200, Jacopo Mondi via libcamera-devel wrote:
> Hi Umang,
>   I'm applying comments on top of Kierans' RFC and I have two
> questions here
> > > index 2f6bb672f7bb..55e82cd404f4 100644
> > > --- a/src/ipa/ipu3/ipu3.cpp
> > > +++ b/src/ipa/ipu3/ipu3.cpp
> > > @@ -38,6 +38,8 @@
> > >   #include "algorithms/tone_mapping.h"
> > >   #include "libipa/camera_sensor_helper.h"
> > > +#include "ipa_context.h"
> > > +
> > >   /* Minimum grid width, expressed as a number of cells */
> > >   static constexpr uint32_t kMinGridWidth = 16;
> > >   /* Maximum grid width, expressed as a number of cells */
> > > @@ -456,8 +458,7 @@ int IPAIPU3::configure(const IPAConfigInfo &configInfo,
> > >   	/* Clean IPAActiveState at each reconfiguration. */
> > >   	context_.activeState = {};
> > > -	IPAFrameContext initFrameContext;
> > > -	context_.frameContexts.fill(initFrameContext);
> > > +	context_.frameContexts.clear();
> > context_.frameContexts.clear();
> >
> > Should also be done in IPAIPU3::stop().
> >
>
> I understand IPA::configure() is not enough, as we can have star/stop
> sequences without a reconfiguration in between.
>
> But why stop() and not start()
>

replying to myself after having re-read Kieran's reply to the comment:
start() can conflict with queueRequest().