[libcamera-devel] [PATCH 2/9] libcamera: delayed_controls: Add helper for controls that applies with a delay
Niklas Söderlund
niklas.soderlund at ragnatech.se
Mon Nov 9 23:54:24 CET 2020
Hi Naush,
Thanks for your feedback.
On 2020-11-03 10:27:06 +0000, Naushir Patuck wrote:
> Hi Niklas,
>
> Thank you for your patch. Please see some initial comments below.
>
> Best regards,
> Naush
>
>
> On Wed, 28 Oct 2020 at 01:01, Niklas Söderlund <
> niklas.soderlund at ragnatech.se> 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.
> >
> > 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
> > + */
> >
>
> Given this is heavily derived from the staggered_write work, would it be ok
> to keep the Raspberry Pi copyright in the header?
>
> Copyright (C) 2020, Raspberry Pi (Trading) Ltd.
As discussed of-band this was always my intention, my templates got in
the way. Sorry about that and thanks for pointing it out.
>
>
> > +#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
> > + {
> > + 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_;
> > +
> > + 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
> > + */
> >
>
> Similar to above:
> Copyright (C) 2020, Raspberry Pi (Trading) Ltd.
>
>
> > +
> > +#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
> > + *
> > + * Some sensor controls take effect with a delay as the sensor needs time
> > to
> > + * adjust, for example exposure and focus. This is an optional helper
> > class to
> > + * deal with such controls and the intended user is 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.
> > + *
> > + * 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.
> > + */
> > +
> > +
> > +/**
> > + * \brief Construct a DelayedControls
> > + * \param[in] device The V4L2 device containing the delayed controls
> > + * \param[in] delays Map of numerical V4L2 control id to its delay to take
> > + * effect 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.
> > + */
> > +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
> > + * exposed byt the device.
> > + */
> > + 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
> > + * device. If no delay is specified assume the control applies
> > directly.
> > + */
> > + 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]);
> > + }
> >
>
> Could you combine the two loops here into one here? If you iterate over
> "delays", you could do the error check as well as adding to the "delays_"
> map.
Good call!
>
> +
> > + reset();
> >
>
> Does this need to be called here? But my understanding of reset() may be
> wrong... see below.
It does as reset() initialize the internal state machine.
>
>
> > +}
> > +
> > +/**
> > + * \brief Reset the V4L2 device
> > + * \param[in] controls List of controls to reset the device to or nullptr
> > + *
> > + * 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);
> >
>
> Should this happen here in reset()? The reset method to me indicates that
> some internal state of the class is meant to be reset, and it does nothing
> to send controls to the device. Writing to the device could happen from
> the caller, if they desire.
Maybe this should be renamed to init() and the argument to
initialControls? As this function should only be called when we are not
streaming I see no harm in optionally allowing a init value. But maybe
this goes hand in had with your follow up comment below.
>
>
> > +
> > + /* 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_++;
> > +}
> >
>
> I'm a bit unclear what reset() does here. In staggered_writer, reset()
> would essentially clear the queues and re-initialise with the last value
> that was set. This seems to pull the value from the device, and put it
> into the queue as a starting point. When we start streaming a sensor, the
> settings will be applied without delay. So if we want to intialise the
> sensor with a new set of controls, it would not work here. Also, if we
> were running a use case where we needed to do a mode switch (e.g. preview
> then capture), then the last requested preview controls would not be used
> to seed the list, and would be lost.
Is this not the same thing but without having to cache it? What ever
controls are set on the device when we stop streaming are our starting
point. IIRC in StaggerdCtrls the initial value may not have been put to
the device but only been at the top of the queue when the streaming
stopped. Another advantage of reading it back here is that we will catch
any control changes done elsewhere in the pipeline perhaps as part of
configure().
>
>
> > +
> > +/**
> > + * \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;
> >
>
> Could you add an error log message here? Do you think this should be a
> continue, my inclination is that return false is the right thing?
I think this should fail as a control was queued which delay is unknown.
>
>
> > +
> > + 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_);
> >
>
> Probably my misunderstanding, but will firstSequence ever be anything but 0?
Unfortunately yes. Some V4L2 drivers does not reset their sequence
number to 0 when starting to stream. So reputing start/stop may have the
first frame seq+1 from the previous stop.
>
>
> > +
> > + 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;
> > + }
> >
>
> As above, can firstSequence_ be anything but 0?
>
>
> > +
> > + /*
> > + * 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
> >
> >
--
Regards,
Niklas Söderlund
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