[libcamera-devel] [PATCH v3 7/8] libcamera: camera: Add CameraConfiguration

Mon Apr 8 14:23:25 CEST 2019

Hi Niklas,

On Mon, Apr 08, 2019 at 01:34:31PM +0200, Niklas Söderlund wrote:
> On 2019-04-06 20:10:32 +0300, Laurent Pinchart wrote:
> > On Sat, Apr 06, 2019 at 08:01:00PM +0300, Laurent Pinchart wrote:
> >> On Sat, Apr 06, 2019 at 01:58:41AM +0200, Niklas Söderlund wrote:
> >>> To properly support both multiple streams and stream usages the library
> >>> must provide a method to map the stream usages to the returned streams
> >>> configurations. Add a camera configuration object to handle this
> >>> mapping.
> >>> 
> >>> Applications can iterate over the returned camera configuration to
> >>> retrieve the streams selected by the library in the same order as the
> >>> usages it provided to the library.
> >>> 
> >>> Application can use the operator[] to retrieve the stream pointer and
> >>> the stream configuration. Using a numerical index retrieves the stream
> >>> pointer, the numerical indexes corresponds to the insertion order of
> >>> usages by the application, using the stream pointer retrieves the
> >>> stream's configuration.
> >>> 
> >>> Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> >>> ---
> >>>  include/libcamera/camera.h |  28 ++++++
> >>>  src/libcamera/camera.cpp   | 173 +++++++++++++++++++++++++++++++++++++
> >>>  2 files changed, 201 insertions(+)
> >>> 
> >>> diff --git a/include/libcamera/camera.h b/include/libcamera/camera.h
> >>> index 0386671c902e55e8..8455049151d5c5a2 100644
> >>> --- a/include/libcamera/camera.h
> >>> +++ b/include/libcamera/camera.h
> >>> @@ -24,6 +24,34 @@ class Stream;
> >>>  class StreamConfiguration;
> >>>  class StreamUsage;
> >>>  
> >>> +class CameraConfiguration
> >>> +{
> >>> +public:
> >>> +	using iterator = std::vector<Stream *>::iterator;
> >>> +	using const_iterator = std::vector<Stream *>::const_iterator;
> >>> +
> >>> +	CameraConfiguration();
> >>> +
> >>> +	iterator begin();
> >>> +	iterator end();
> >>> +	const_iterator begin() const;
> >>> +	const_iterator end() const;
> >>> +
> >>> +	bool valid() const;
> >>> +	bool empty() const;
> > 
> > valid() and empty() vs. isValid() and isEmpty() ? I have a preference
> > for the latter due to my Qt bias, but I'm open to discuss this.
> 
> I have no strong opinion on valid() vs isValid() so will bend to popular 
> opinion. For empty() I think we should keep it as is as this class to 
> some degree tries to mimic the std::{vector,map} interface where empty() 
> is used.

I think we should remain consistent and use either empty(), valid() or
isEmpty(), isValid(). STL doesn't use an "is" prefix, Qt does. We have a
few functions with the "is" prefix already, and that's my preference,
but as I aid I'm open to discuss this.

> >>> +	std::size_t size() const;
> >>> +
> >>> +	Stream *front();
> >> 
> >> For completeness, should you have a const Stream *front() const ?
> >> 
> >>> +
> >>> +	Stream *operator[](unsigned int index) const;
> >>> +	StreamConfiguration &operator[](Stream *stream);
> >>> +	const StreamConfiguration &operator[](Stream *stream) const;
> >>> +
> >>> +private:
> >>> +	std::vector<Stream *> order_;
> >>> +	std::map<Stream *, StreamConfiguration> config_;
> >>> +};
> >>> +
> >>>  class Camera final
> >>>  {
> >>>  public:
> >>> diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
> >>> index 63fde0ffc3d02d6c..98145edea1ac9c91 100644
> >>> --- a/src/libcamera/camera.cpp
> >>> +++ b/src/libcamera/camera.cpp
> >>> @@ -39,6 +39,179 @@ namespace libcamera {
> >>>  
> >>>  LOG_DECLARE_CATEGORY(Camera)
> >>>  
> >>> +/**
> >>> + * \class CameraConfiguration
> >>> + * \brief Hold configuration for streams of the camera
> >>> + *
> >>> + * The CameraConfiguration is filled with information by the application either
> >>> + * manually or with the streamConfiguration() helper. The helper takes a list
> >> 
> >> s/streamConfiguration()/Camera::streamConfigure()/ (to get doxygen to
> >> generate a link)
> >> 
> >>> + * of usages describing how the application intends to use streams of the
> >>> + * camera, the application in return are provided with a default camera
> >> 
> >> s/are provided/is provided/
> >> 
> >>> + * configuration it can tune.
> >> 
> >> Maybe s/tune/fine-tune/ ?
> >> 
> >>> + *
> >>> + * Applications iterate over the CameraConfiguration to discover which streams
> >>> + * the camera has associated to the usages, and can inspect the configuration
> >>> + * of individual streams using the operator[].
> >> 
> >> This all explains how to use CameraConfiguration with the
> >> streamConfiguration() helper, which I think belongs more to the helper's
> >> documentation. Here I would explain what the CameraConfiguration is and
> >> how it is used. How about the following ?
> >> 
> >>  * The CameraConfiguration holds an ordered list of streams and their associated
> >>  * StreamConfiguration. From a data storage point of view, the class operates as
> >>  * a map of Stream pointers to StreamConfiguration, with entries accessed with
> >>  * operator[](Stream *). Accessing an entry for a Stream pointer not yet stored
> >>  * in the configuration inserts a new empty entry.
> >>  *
> >>  * The class also suppors iterators, and from that point of view operates as a
> >>  * vector of Stream pointers. The streams are iterated in insertion order, and
> >>  * the operator[](int) returns the Stream pointer based on its insertion index.
> >>  * Accessing a stream with an invalid index returns a null pointer.
> >> 
> >> The text you wrote should be reused to document Camera::streamConfiguration().
> >> 
> >>> + */
> >>> +
> >>> +/**
> >>> + * \typedef CameraConfiguration::iterator
> >>> + * \brief Iterator for the streams in the configuration
> >>> + */
> >>> +
> >>> +/**
> >>> + * \typedef CameraConfiguration::const_iterator
> >>> + * \brief Const iterator for the streams in the configuration
> >>> + */
> >>> +
> >>> +/**
> >>> + * \brief Create an empty camera configuration
> >>> + */
> >>> +CameraConfiguration::CameraConfiguration()
> >>> +	: order_({}), config_({})
> >>> +{
> >>> +}
> >>> +
> >>> +/**
> >>> + * \brief Retrieve an iterator to the first stream in the sequence
> >>> + *
> >>> + * \return An iterator to the first stream
> >>> + */
> >>> +std::vector<Stream *>::iterator CameraConfiguration::begin()
> >>> +{
> >>> +	return order_.begin();
> >>> +}
> >>> +
> >>> +/**
> >>> + * \brief Retrieve an iterator pointing to the past-the-end stream in the
> >>> + * sequence
> >>> + *
> >>> + * \return An iterator to the element following the last stream
> >>> + */
> >>> +std::vector<Stream *>::iterator CameraConfiguration::end()
> >>> +{
> >>> +	return order_.end();
> >>> +}
> >>> +
> >>> +/**
> >>> + * \brief Retrieve an iterator to the first element of the streams
> >> 
> >> Maybe "a const iterator" ?
> >> 
> >>> + *
> >>> + * \return An iterator to the first stream
> >> 
> >> And here too, and for the const version of end() as well.
> >> 
> >>> + */
> >>> +std::vector<Stream *>::const_iterator CameraConfiguration::begin() const
> >>> +{
> >>> +	return order_.begin();
> >>> +}
> >>> +
> >>> +/**
> >>> + * \brief Retrieve an iterator to the end of the streams
> >> 
> >> The non-const version mentions past-the-end.
> >> 
> >>> + *
> >>> + * \return An iterator to the element following the last stream
> >>> + */
> >>> +std::vector<Stream *>::const_iterator CameraConfiguration::end() const
> >>> +{
> >>> +	return order_.end();
> >>> +}
> >>> +
> >>> +/**
> >>> + * \brief Check if the camera configuration is valid
> >> 
> >> I think you should explain what an invalid configuration is.
> >> 
> >>> + *
> >>> + * \return True if the configuration is valid
> >>> + */
> >>> +bool CameraConfiguration::valid() const
> >>> +{
> >>> +	if (empty())
> >>> +		return false;
> >>> +
> >>> +	for (auto const &it : config_) {
> >>> +		const StreamConfiguration &conf = it.second;
> >>> +
> >>> +		if (conf.width == 0 || conf.height == 0 ||
> >>> +		    conf.pixelFormat == 0 || conf.bufferCount == 0)
> >>> +			return false;
> >> 
> >> Do we have use cases for a non-empty CameraConfiguration with invalid
> >> StreamConfiguration ? Or is it just for completeness ?
> >> 
> >>> +	}
> >>> +
> >>> +	return true;
> >>> +}
> >>> +
> >>> +/**
> >>> + * \brief Check if the camera configuration is empty
> >>> + *
> >>> + * \return True if the configuration is empty
> >>> + */
> >>> +bool CameraConfiguration::empty() const
> >>> +{
> >>> +	return order_.empty();
> >>> +}
> >>> +
> >>> +/**
> >>> + * \brief Retrieve the number of stream configurations
> >>> + *
> >>> + * \return Number of stream configurations
> >>> + */
> >>> +std::size_t CameraConfiguration::size() const
> >>> +{
> >>> +	return order_.size();
> >>> +}
> >>> +
> >>> +/**
> >>> + * \brief Access the first stream in the configuration
> >>> + *
> >>> + * \return The first stream in the configuration
> >>> + */
> >>> +Stream *CameraConfiguration::front()
> >>> +{
> >>> +	return order_.front();
> >>> +}
> >>> +/**
> >>> + * \brief Retrieve a stream pointer from index
> >>> + * \param[in] index Numerical index
> >>> + *
> >>> + * The \a index represents the zero bases insertion order of stream and stream
> >> 
> >> s/bases/based/
> >> 
> >>> + * configuration into the camera configuration.
> >>> + *
> >>> + * \return The stream pointer at index, or a nullptr if the index is out of
> >>> + * bounds
> >>> + */
> >>> +Stream *CameraConfiguration::operator[](unsigned int index) const
> >>> +{
> >>> +	if (index >= order_.size())
> >>> +		return nullptr;
> >>> +
> >>> +	return order_.at(index);
> >>> +}
> >>> +
> >>> +/**
> >>> + * \brief Retrieve a reference to a stream configuration
> >>> + * \param[in] stream Stream to retrieve configuration for
> >>> + *
> >>> + * If the camera configuration does not yet contain a configuration for
> >>> + * the requested stream, create and return an empty stream configuration.
> >>> + *
> >>> + * \return The configuration for the stream
> >>> + */
> >>> +StreamConfiguration &CameraConfiguration::operator[](Stream *stream)
> >>> +{
> >>> +	if (config_.find(stream) == config_.end())
> >>> +		order_.push_back(stream);
> >>> +
> >>> +	return config_[stream];
> >>> +}
> >>> +
> >>> +/**
> >>> + * \brief Retrieve a const reference to a stream configuration
> >>> + * \param[in] stream Stream to retrieve configuration for
> >>> + *
> >>> + * No new stream configuration is created if called with \a stream that is not
> >>> + * already part of the camera configuration, doing so is an illegal operation.
> >> 
> >> s/illegal/invalid/ ?
> >> 
> >> I would also say "and results in undefined behaviour" as the std::map
> >> will throw an exception.
> >> 
> >>> + *
> >>> + * \return The configuration for the stream
> >>> + */
> >>> +const StreamConfiguration &CameraConfiguration::operator[](Stream *stream) const
> >>> +{
> >>> +	return config_.at(stream);
> >>> +}
> >>> +
> >>>  /**
> >>>   * \class Camera
> >>>   * \brief Camera device

-- 
Regards,

Laurent Pinchart