[libcamera-devel] [PATCH 2/9] libcamera: delayed_controls: Add helper for controls that applies with a delay
Naushir Patuck
naush at raspberrypi.com
Wed Nov 4 17:18:00 CET 2020
Hi Jacopo and Niklas,
On Wed, 4 Nov 2020 at 16:08, Jacopo Mondi <jacopo at jmondi.org> wrote:
> Hi Niklas,
>
> On Wed, Oct 28, 2020 at 02:00:44AM +0100, Niklas Söderlund wrote:
> > Some sensor controls take effect with a delay as the sensor needs time
> > to adjust, for example exposure. Add a optional helper DelayedControls
> > to help pipelines deal with such controls.
> >
> > The idea is to provide a queue of controls towards the V4L2 device and
> > apply individual controls with the specified delay with the aim to get
> > predictable and retrievable control values for any given frame. To do
> > this the queue of controls needs to be at least as deep as the control
> > with the largest delay.
> >
> > The DelayedControls needs to be informed of every start of exposure.
> > This can be emulated but the helper is designed to be used with this
> > event being provide by the kernel thru V4L2 events.
>
> s/thru/though ?
> >
> > This helper is based on StaggeredCtrl from the Raspberry Pi pipeline
> > handler but expands on its API. This helpers aims to replace the
> > Raspberry Pi implementations and mimics it behavior perfectly.
> >
> > Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> > ---
> > include/libcamera/internal/delayed_controls.h | 87 ++++++
> > src/libcamera/delayed_controls.cpp | 282 ++++++++++++++++++
> > src/libcamera/meson.build | 1 +
> > 3 files changed, 370 insertions(+)
> > create mode 100644 include/libcamera/internal/delayed_controls.h
> > create mode 100644 src/libcamera/delayed_controls.cpp
> >
> > diff --git a/include/libcamera/internal/delayed_controls.h
> b/include/libcamera/internal/delayed_controls.h
> > new file mode 100644
> > index 0000000000000000..df5520d240a54e4b
> > --- /dev/null
> > +++ b/include/libcamera/internal/delayed_controls.h
> > @@ -0,0 +1,87 @@
> > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > +/*
> > + * Copyright (C) 2020, Google Inc.
> > + *
> > + * delayed_controls.h - Helper to deal with controls that are applied
> with a delay
> > + */
> > +#ifndef __LIBCAMERA_INTERNAL_DELAYED_CONTROLS_H__
> > +#define __LIBCAMERA_INTERNAL_DELAYED_CONTROLS_H__
> > +
> > +#include <mutex>
> > +#include <stdint.h>
> > +#include <unordered_map>
> > +
> > +#include <libcamera/controls.h>
> > +
> > +namespace libcamera {
> > +
> > +class V4L2Device;
> > +
> > +class DelayedControls
> > +{
> > +public:
> > + DelayedControls(V4L2Device *device,
> > + const std::unordered_map<uint32_t, unsigned int>
> &delays);
> > +
> > + void reset(ControlList *controls = nullptr);
> > +
> > + bool push(const ControlList &controls);
> > + ControlList get(uint32_t sequence);
> > +
> > + void frameStart(uint32_t sequence);
> > +
> > +private:
> > + class ControlInfo
>
> With no other scope but public:, is it worth a class ?
>
> > + {
> > + public:
> > + ControlInfo()
> > + : updated(false)
> > + {
> > + }
> > +
> > + ControlInfo(const ControlValue &v)
> > + : value(v), updated(true)
> > + {
> > + }
> > +
> > + ControlValue value;
> > + bool updated;
> > + };
> > +
> > + static constexpr int listSize = 16;
> > + class ControlArray : public std::array<ControlInfo, listSize>
> > + {
> > + public:
> > + ControlInfo &operator[](unsigned int index)
> > + {
> > + return std::array<ControlInfo,
> listSize>::operator[](index % listSize);
> > + }
> > +
> > + const ControlInfo &operator[](unsigned int index) const
> > + {
> > + return std::array<ControlInfo,
> listSize>::operator[](index % listSize);
> > + }
> > + };
> > +
> > + using ControlsDelays = std::unordered_map<const ControlId *,
> unsigned int>;
> > + using ControlsValues = std::unordered_map<const ControlId *,
> ControlArray>;
> > +
> > + bool queue(const ControlList &controls);
> > +
> > + std::mutex lock_;
> > +
> > + V4L2Device *device_;
> > + ControlsDelays delays_;
> > + unsigned int maxDelay_;
> > +
> > + bool running_;
> > + uint32_t fistSequence_;
>
> Should this be 'first' ?
>
> > +
> > + uint32_t queueCount_;
> > + uint32_t writeCount_;
> > + ControlsValues ctrls_;
> > +};
> > +
> > +} /* namespace libcamera */
> > +
> > +#endif /* __LIBCAMERA_INTERNAL_DELAYED_CONTROLS_H__ */
> > diff --git a/src/libcamera/delayed_controls.cpp
> b/src/libcamera/delayed_controls.cpp
> > new file mode 100644
> > index 0000000000000000..0e32f417c5cc68b7
> > --- /dev/null
> > +++ b/src/libcamera/delayed_controls.cpp
> > @@ -0,0 +1,282 @@
> > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > +/*
> > + * Copyright (C) 2020, Google Inc.
> > + *
> > + * delayed_controls.h - Helper to deal with controls that are applied
> with a delay
> > + */
> > +
> > +#include "libcamera/internal/delayed_controls.h"
> > +#include "libcamera/internal/v4l2_device.h"
> > +
> > +#include <libcamera/controls.h>
> > +
> > +#include "libcamera/internal/log.h"
> > +
> > +/**
> > + * \file delayed_controls.h
> > + * \brief Helper to deal with controls that are applied with a delay
> > + */
> > +
> > +namespace libcamera {
> > +
> > +LOG_DEFINE_CATEGORY(DelayedControls)
> > +
> > +/**
> > + * \class DelayedControls
> > + * \brief Helper to deal with controls that takes effect with a delay
>
> controls -> take
>
> > + *
> > + * Some sensor controls take effect with a delay as the sensor needs
> time to
>
> controls -> take
>
> > + * adjust, for example exposure and focus. This is an optional helper
> class to
> > + * deal with such controls and the intended user is pipeline handlers.
>
> users are pipeline handlers
>
> > + *
> > + * The idea is to extend the concept of the pipeline depth the users
> needs to
> > + * maintain for buffers to controls. The depth is determined with by
> the control
> > + * with the grates delay. As long as the pipeline keeps the control
> queue above
> > + * this level the control values are guaranteed to be in effect at the
> specified
> > + * point in time.
>
> I would drop this as it mentions other concepts that might be more
> confusing than helping.
>
> > + *
> > + * The downside is of course that the pipeline needs to know what
> controls to
> > + * set control depth frames in advance. But there really is no way
> around this
> > + * as the delay is a consequence of the physical world. Compare this
> with
> > + * parameter buffers where the buffer may be queued to the device while
> it's
> > + * still being written to as long as it's ready before it's consumed,
> this is
> > + * because the parameter buffer (usually) does not contain controls that
> > + * requires time to take effect.
>
> I find this confusing too, I'm sorry.
>
> I think the key concept is that controls have to be applied in
> advance, the usage of "Delayed" took me a bit off-road as a
> DelayedControls class seems to be designed to apply controls at a
> later (delayed) point in time while it's actually the other way
> around. One key point is that for each Control the pipeline handler
> has to provide a known delay value, something I didn't realize until I
> looked at the code. The class takes care of applying the control the
> control in -advance- enough to make sure the control is fully applied
> at the time the Request it is associated to completes.
>
Just wanted to add a bit to this. The intention of this class (and the
parent staggered write class) for the Raspberry Pi pipeline is to ensure
that gain/exposure/vblank/etc. get *applied* by the sensor on the same
frame even though the relative delays between each control will be
different. This does not bear any relation to synchronising with a Request
- although it could be adapted for that. If the use of "Delayed" may cause
confusion, perhaps we can use "Staggered" to indicate control writes are
staggered to account for the relative delay differences, but I am biased in
that choice ;-)
Regards,
Naush
>
> In the class description I would describe what the class offers and
> how it has to be used, its API and how I should set
> controls specifying their 'delay'. Design documentation is good but
> only to complement usage documentation.
>
> > + */
> > +
> > +
> > +/**
> > + * \brief Construct a DelayedControls
> > + * \param[in] device The V4L2 device containing the delayed controls
>
> The V4L2 device the controls have to be applied to
>
> > + * \param[in] delays Map of numerical V4L2 control id to its delay to
> take
> > + * effect in frames
>
> isn't 'latency' better than delay ? Or any other term ? See how heavy
> is the description you had to make of this parameter...
>
> \param[in] delays Map of V4L2 control ids and their associated latencies
> (in frames)
>
> ?
> > + *
> > + * Only controls specified in \a delays are handled by the
> DelayedControls
> > + * instance. If it's desired to mix delayed controls and controls that
> takes
> > + * effect immediately the immediate controls must be listed in the \a
> delays map
> > + * with a delay value of 0.
>
> delays is a map, you have to provide a delay value by design
>
> "Controls with an associated 0 delay (latency) are applied immediately"
>
>
> > + */
> > +DelayedControls::DelayedControls(V4L2Device *device,
> > + const std::unordered_map<uint32_t,
> unsigned int> &delays)
> > + : device_(device), maxDelay_(0)
> > +{
> > + const ControlInfoMap &controls = device_->controls();
> > +
> > + /*
> > + * Sanity check that all controls where delays are requested are
>
> s/where delays//
>
> > + * exposed byt the device.
>
> by
>
> > + */
> > + for (auto const &delay : delays) {
> > + unsigned int id = delay.first;
> > +
> > + if (controls.find(id) == controls.end())
> > + LOG(DelayedControls, Error)
> > + << "Delay request for control id "
> > + << utils::hex(id)
> > + << " but control is not exposed by device "
> > + << device_->deviceNode();
> > + }
> > +
> > + /*
> > + * Create a map of control to delay for all controls exposed by the
>
> controls to delays
>
> > + * device. If no delay is specified assume the control applies
> directly.
>
> assume a 0 delay (latency)
>
> > + */
> > + for (auto const &control : controls) {
> > + const ControlId *id = control.first;
> > +
> > + auto it = delays.find(id->id());
> > + if (it == delays.end())
> > + continue;
> > +
> > + delays_[id] = it->second;
> > +
> > + LOG(DelayedControls, Debug)
> > + << "Set a delay of " << delays_[id]
> > + << " for " << id->name();
> > +
> > + maxDelay_ = std::max(maxDelay_, delays_[id]);
> > + }
> > +
> > + reset();
> > +}
> > +
> > +/**
> > + * \brief Reset the V4L2 device
>
> Reset controls to their default values ?
>
> > + * \param[in] controls List of controls to reset the device to or
> nullptr
>
> Optional list of controls to apply to the device ?
>
> These is mostly on documentation, I'll look at implementation later!
>
> Thanks
> j
>
>
> > + *
> > + * Resets the delayed controls state machine to its starting state. All
> controls
> > + * are fetched from the V4L2 device to provide a good starting point
> for the
> > + * first frames (length of control depth).
> > + *
> > + * Optionally \a controls can be specified to set some or all of the
> handled
> > + * V4L2 controls prior to reading them back. If no controls needs to be
> set
> > + * nullptr may be used.
> > + */
> > +void DelayedControls::reset(ControlList *controls)
> > +{
> > + std::lock_guard<std::mutex> lock(lock_);
> > +
> > + running_ = false;
> > + fistSequence_ = 0;
> > + queueCount_ = 0;
> > + writeCount_ = 0;
> > +
> > + /* Set the controls on the device if requested. */
> > + if (controls)
> > + device_->setControls(controls);
> > +
> > + /* Retrieve current control values reported by the device. */
> > + std::vector<uint32_t> ids;
> > + for (auto const &delay : delays_)
> > + ids.push_back(delay.first->id());
> > +
> > + ControlList devCtrls = device_->getControls(ids);
> > +
> > + /* Seed the control queue with the controls reported by the
> device. */
> > + ctrls_.clear();
> > + for (const auto &ctrl : devCtrls) {
> > + const ControlId *id =
> devCtrls.infoMap()->idmap().at(ctrl.first);
> > + ctrls_[id][queueCount_] = ControlInfo(ctrl.second);
> > + }
> > +
> > + queueCount_++;
> > +}
> > +
> > +/**
> > + * \brief Push a set of controls on the queue
> > + * \param[in] controls List of controls to add the device queue
> > + *
> > + * Push a set of controls to the control queue. This increases the
> control queue
> > + * depth by one.
> > + *
> > + * \returns true if \a controls are accepted, or false otherwise
> > + */
> > +bool DelayedControls::push(const ControlList &controls)
> > +{
> > + std::lock_guard<std::mutex> lock(lock_);
> > +
> > + return queue(controls);
> > +}
> > +
> > +bool DelayedControls::queue(const ControlList &controls)
> > +{
> > + /* Copy state from previous frame. */
> > + for (auto &ctrl : ctrls_) {
> > + ControlInfo &info = ctrls_[ctrl.first][queueCount_];
> > + info.value = ctrls_[ctrl.first][queueCount_ - 1].value;
> > + info.updated = false;
> > + }
> > +
> > + /* Update with new controls. */
> > + for (const auto &control : controls) {
> > + const ControlId *id =
> device_->controls().idmap().at(control.first);
> > +
> > + if (delays_.find(id) == delays_.end())
> > + return false;
> > +
> > + ControlInfo &info = ctrls_[id][queueCount_];
> > +
> > + info.value = control.second;
> > + info.updated = true;
> > +
> > + LOG(DelayedControls, Debug)
> > + << "Queuing " << id->name()
> > + << " to " << info.value.toString()
> > + << " at index " << queueCount_;
> > + }
> > +
> > + queueCount_++;
> > +
> > + return true;
> > +}
> > +
> > +/**
> > + * \brief Read back controls in effect at a specific sequence number
> > + * \param[in] sequence Sequence number to get read back controls for
> > + *
> > + * Read back what controls where in effect at a specific sequence
> number. The
> > + * history is a ring buffer of 16 entries where new and old values
> coexist. It's
> > + * the callers responsibility to not read to old sequence numbers that
> have been
> > + * pushed out of the history.
> > + *
> > + * Historic values are evicted by pushing new values onto the queue
> using
> > + * push(). The max history from the current sequence number that yields
> valid
> > + * values are thus 16 minus number of controls pushed.
> > + *
> > + * \returns List of controls in effect at \a sequence
> > + */
> > +ControlList DelayedControls::get(uint32_t sequence)
> > +{
> > + std::lock_guard<std::mutex> lock(lock_);
> > +
> > + uint32_t adjustedSeq = sequence - fistSequence_ + 1;
> > + unsigned int index = std::max<int>(0, adjustedSeq - maxDelay_);
> > +
> > + ControlList out(device_->controls());
> > + for (const auto &ctrl : ctrls_) {
> > + const ControlId *id = ctrl.first;
> > + const ControlInfo &info = ctrl.second[index];
> > +
> > + out.set(id->id(), info.value);
> > +
> > + LOG(DelayedControls, Debug)
> > + << "Reading " << id->name()
> > + << " to " << info.value.toString()
> > + << " at index " << index;
> > + }
> > +
> > + return out;
> > +}
> > +
> > +/**
> > + * \brief Inform DelayedControls of a start of a new frame
> > + * \param[in] sequence Sequence number of the frame that started
> > + *
> > + * Inform the state machine that a new frame have started and it's
> sequence
> > + * number. It's user of this helpers responsibility to inform the helper
> > + * at the start of every frame. This can with ease be connected to the
> start
> > + * of exposure (SOE) V4L2 event.
> > + */
> > +void DelayedControls::frameStart(uint32_t sequence)
> > +{
> > + LOG(DelayedControls, Debug) << "frame " << sequence << " started";
> > +
> > + std::lock_guard<std::mutex> lock(lock_);
> > +
> > + if (!running_) {
> > + fistSequence_ = sequence;
> > + running_ = true;
> > + }
> > +
> > + /*
> > + * Create control list peaking ahead in the value queue to ensure
> > + * values are set in time to satisfy the sensor delay.
> > + */
> > + ControlList out(device_->controls());
> > + for (const auto &ctrl : ctrls_) {
> > + const ControlId *id = ctrl.first;
> > + unsigned int delayDiff = maxDelay_ - delays_[id];
> > + unsigned int index = std::max<int>(0, writeCount_ -
> delayDiff);
> > + const ControlInfo &info = ctrl.second[index];
> > +
> > + if (info.updated) {
> > + out.set(id->id(), info.value);
> > + LOG(DelayedControls, Debug)
> > + << "Setting " << id->name()
> > + << " to " << info.value.toString()
> > + << " at index " << index;
> > + }
> > + }
> > +
> > + writeCount_++;
> > +
> > + while (writeCount_ >= queueCount_) {
> > + LOG(DelayedControls, Debug)
> > + << "Queue is empty, auto queue no-op.";
> > + queue({});
> > + }
> > +
> > + device_->setControls(&out);
> > +}
> > +
> > +} /* namespace libcamera */
> > diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
> > index 07711b5f93bcc921..19f22f9c94e1d64d 100644
> > --- a/src/libcamera/meson.build
> > +++ b/src/libcamera/meson.build
> > @@ -12,6 +12,7 @@ libcamera_sources = files([
> > 'controls.cpp',
> > 'control_serializer.cpp',
> > 'control_validator.cpp',
> > + 'delayed_controls.cpp',
> > 'device_enumerator.cpp',
> > 'device_enumerator_sysfs.cpp',
> > 'event_dispatcher.cpp',
> > --
> > 2.29.1
> >
> > _______________________________________________
> > libcamera-devel mailing list
> > libcamera-devel at lists.libcamera.org
> > https://lists.libcamera.org/listinfo/libcamera-devel
>
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