[libcamera-devel] [PATCH v3 02/12] libcamera: camera: Introduce SensorConfiguration

[Laurent Pinchart]

Another small comment.
G
On Fri, Sep 15, 2023 at 07:06:15PM +0300, Laurent Pinchart via libcamera-devel wrote:
> On Fri, Sep 15, 2023 at 03:06:40PM +0200, Jacopo Mondi via libcamera-devel wrote:
> > Introduce SensorConfiguration in the libcamera API.
> > 
> > The SensorConfiguration is part of the CameraConfiguration class
> > and allows applications to control the sensor settings.
> > 
> > Signed-off-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
> > Reviewed-by: Naushir Patuck <naush at raspberrypi.com>
> > Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> > ---
> >  include/libcamera/camera.h |  43 +++++++++
> >  src/libcamera/camera.cpp   | 185 +++++++++++++++++++++++++++++++++++++
> >  2 files changed, 228 insertions(+)
> > 
> > diff --git a/include/libcamera/camera.h b/include/libcamera/camera.h
> > index 004bc89455f5..b2aa8d467feb 100644
> > --- a/include/libcamera/camera.h
> > +++ b/include/libcamera/camera.h
> > @@ -19,6 +19,7 @@
> >  #include <libcamera/base/signal.h>
> >  
> >  #include <libcamera/controls.h>
> > +#include <libcamera/geometry.h>
> >  #include <libcamera/request.h>
> >  #include <libcamera/stream.h>
> >  #include <libcamera/transform.h>
> > @@ -30,6 +31,47 @@ class FrameBufferAllocator;
> >  class PipelineHandler;
> >  class Request;
> >  
> > +class SensorConfiguration
> > +{
> > +public:
> > +	unsigned int bitDepth = 0;
> > +
> > +	Rectangle analogCrop;
> > +
> > +	struct {
> > +		unsigned int binX = 1;
> > +		unsigned int binY = 1;
> > +	} binning;
> > +
> > +	struct {
> > +		unsigned int xOddInc = 1;
> > +		unsigned int xEvenInc = 1;
> > +		unsigned int yOddInc = 1;
> > +		unsigned int yEvenInc = 1;
> 
> What's the reason for exposing the odd and even increments separately,
> instead of a skipping factor ?
> 
> > +	} skipping;
> > +
> > +	Size outputSize;
> > +
> > +	bool valid() const
> > +	{
> > +		return validate() != Invalid;
> > +	}
> > +
> > +	explicit operator bool() const
> > +	{
> > +		return validate() == Populated;
> > +	}
> > +
> > +private:
> > +	enum Status {
> > +		Unpopulated,
> > +		Populated,
> > +		Invalid,
> > +	};
> > +
> > +	Status validate() const;
> > +};
> > +
> >  class CameraConfiguration
> >  {
> >  public:
> > @@ -66,6 +108,7 @@ public:
> >  	bool empty() const;
> >  	std::size_t size() const;
> >  
> > +	SensorConfiguration sensorConfig;
> >  	Transform transform;
> >  
> >  protected:
> > diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
> > index 0eecee766f00..f497a35c90fb 100644
> > --- a/src/libcamera/camera.cpp
> > +++ b/src/libcamera/camera.cpp
> > @@ -97,6 +97,21 @@
> >   * implemented in the above order at the hardware level. The libcamera pipeline
> >   * handlers translate the pipeline model to the real hardware configuration.
> >   *
> > + * \subsection camera-sensor-mode Camera Sensor Model
> 
> s/-mode/-model/
> 
> > + *
> > + * libcamera allows applications to control the configuration of the camera
> > + * sensor, particularly it allows to control the frame geometry and frame
> > + * delivery rate of the sensor.
> 
> s/delivery //
> 
> I'd like to make it clear that this is optional:
> 
>  * By default, libcamera configures the camera sensor automatically based on the
>  * configuration of the streams. Applications may instead specify a manual
>  * configuration for the camera sensor. This allows precise control of the frame
>  * geometry and frame rate delivered by the sensor.
> 
> > + *
> > + * The camera sensor configuration applies to all streams produced by a camera
> > + * from the same image source.
> 
> This paragraph should go to CameraConfiguration::sensorConfig below.
> 
> > + *
> > + * More details about the camera sensor model implemented by libcamera are
> > + * available in the libcamera camera-sensor-model documentation page.
> > + *
> > + * The sensor configuration is specified by applications by populating the
> > + * CameraConfiguration::sensorConfig class member.
> 
> Drop this paragraph, it doesn't belong to the camera model introduction
> (none of the other sections here go into the level of details).
> 
> > + *
> >   * \subsection digital-zoom Digital Zoom
> >   *
> >   * Digital zoom is implemented as a combination of the cropping and scaling
> > @@ -111,6 +126,166 @@ namespace libcamera {
> >  
> >  LOG_DECLARE_CATEGORY(Camera)
> >  
> > +/**
> > + * \class SensorConfiguration
> > + * \brief Camera sensor configuration
> > + *
> > + * The SensorConfiguration class collects parameters to control the operations
> > + * of the camera sensor, accordingly to the abstract camera sensor model
> 
> s/according/accordingly/
> 
> > + * implemented by libcamera.
> > + *
> > + * \todo Applications shall fully populate all fields of the
> > + * CameraConfiguration::sensorConfig class members before validating the
> > + * CameraConfiguration. If the SensorConfiguration is not fully populated, or if
> > + * any of its parameters cannot be applied to the sensor in use, the
> > + * CameraConfiguration validation process will fail and return
> > + * CameraConfiguration::Status::Invalid.
> > + *
> > + * Applications that populate the SensorConfiguration class members are
> > + * expected to be highly-specialized applications that know what sensor
> > + * they are operating with and what parameters are valid for the sensor in use.
> > + *
> > + * A detailed description of the abstract camera sensor model implemented by
> > + * libcamera and the description of its configuration parameters is available
> > + * in the libcamera documentation camera-sensor-model file.
> > + */
> > +
> > +/**
> > + * \enum SensorConfiguration::Status
> > + * \brief The sensor configuration validation status
> > + */
> > +
> > +/**
> > + * \var SensorConfiguration::bitDepth
> > + * \brief The sensor image format bit depth
> > + *
> > + * The number of bits (resolution) used to represent a pixel sample.
> > + */
> > +
> > +/**
> > + * \var SensorConfiguration::analogCrop
> > + * \brief The analog crop rectangle
> > + *
> > + * The selected portion of the active pixel array used to produce the image
> > + * frame.
> > + */
> > +
> > +/**
> > + * \var SensorConfiguration::binning
> > + * \brief Sensor binning configuration
> > + *
> > + * Refer to the camera-sensor-model documentation for an accurate description
> > + * of the binning operations. Disabled by default.
> > + */
> > +
> > +/**
> > + * \var SensorConfiguration::binX
> > + * \brief Horizontal binning factor
> > + *
> > + * The horizontal binning factor. Default to 1.
> > + */
> > +
> > +/**
> > + * \var SensorConfiguration::binY
> > + * \brief Vertical binning factor
> > + *
> > + * The vertical binning factor. Default to 1.
> > + */
> > +
> > +/**
> > + * \var SensorConfiguration::skipping
> > + * \brief The sensor skipping configuration
> > + *
> > + * Refer to the camera-sensor-model documentation for an accurate description
> > + * of the skipping operations.
> > + *
> > + * If no skipping is performed, all the structure fields should be
> > + * set to 1. Disabled by default.
> > + */
> > +
> > +/**
> > + * \var SensorConfiguration::xOddInc
> > + * \brief Horizontal increment for odd rows. Default to 1.
> > + */
> > +
> > +/**
> > + * \var SensorConfiguration::xEvenInc
> > + * \brief Horizontal increment for even rows. Default to 1.
> > + */
> > +
> > +/**
> > + * \var SensorConfiguration::yOddInc
> > + * \brief Vertical increment for odd columns. Default to 1.
> > + */
> > +
> > +/**
> > + * \var SensorConfiguration::yEvenInc
> > + * \brief Vertical increment for even columns. Default to 1.
> > + */
> > +
> > +/**
> > + * \var SensorConfiguration::outputSize
> > + * \brief The frame output (visible) size
> > + *
> > + * The size of the data frame as received by the host processor.
> > + */
> > +
> > +/**
> > + * \fn SensorConfiguration::valid() const
> > + * \brief Validate the SensorConfiguration
> > + *
> > + * Validate the sensor configuration.
> > + *
> > + * \todo A sensor configuration is valid (or well-formed) if it's either
> > + * completely un-populated or fully populated. For now allow applications to
> > + * populate the bitDepth and the outputSize only.
> 
> As I've mentioned before (so it shouldn't come as a surprise), I think
> this is a hack (and I think we agree :-)). I'm OK with it in the very
> short term, but with IMX519 support that should arrive soon, we'll need
> to do better. The IMX519 will likely be supported by the ccs kernel
> driver, which isn't mode-based. Configuring the sensor solely through
> the output resolution won't work. I plan to rework the CameraSensor
> class to support ccs-based sensors, and as part of that work, I will
> most likely address this todo item and probably require applications to
> select a full sensor configuration.
> 
> This doesn't require any immediate change. I've CC'ed David and Naush as
> RPi is the first user of this API, and I don't want changes in the near
> future to come as a surprise.
> 
> > + *
> > + * \return True if the SensorConfiguration is either fully populated or
> > + * un-populated, false otherwise
> > + */
> > +
> > +/**
> > + * \fn SensorConfiguration::operator bool() const

Would this be better turned into a function with an explicit name (such
as populated()) instead of a conversion operator ? Writing

	if (config)
		...

doesn't make it immediately clear to the reader what is being tested.

> > + * \brief Test if a SensorConfiguration is fully populated
> > + * \return True if the SensorConfiguration is fully populated
> > + */
> > +
> > +/**
> > + * \brief Validate the sensor configuration
> > + *
> > + * \todo A sensor configuration is valid (or well-formed) if it's either
> > + * completely un-populated or fully populated. For now allow applications to
> > + * populate the bitDepth and the outputSize only.
> > + *
> > + * \return The sensor configuration status
> > + * \retval Unpopulated The sensor configuration is fully unpopulated
> > + * \retval Populated The sensor configuration is fully populated
> > + * \retval Invalid The sensor configuration is invalid (not fully populated
> > + * and not fully unpopulated)
> > + */
> > +SensorConfiguration::Status SensorConfiguration::validate() const
> > +{
> > +	if (bitDepth && binning.binX && binning.binY &&
> > +	    skipping.xOddInc && skipping.yOddInc &&
> > +	    skipping.xEvenInc && skipping.yEvenInc &&
> > +	    !outputSize.isNull())
> > +		return Populated;
> > +
> > +	/*
> > +	 * By default the binning and skipping factors are initialized to 1, but
> > +	 * a zero-initialized SensorConfiguration is considered unpopulated
> > +	 * as well.
> > +	 */
> > +	if (!bitDepth &&
> > +	    binning.binX <= 1 && binning.binY <= 1 &&
> > +	    skipping.xOddInc <= 1 && skipping.yOddInc <= 1 &&
> > +	    skipping.xEvenInc <= 1 && skipping.yEvenInc <= 1 &&
> > +	    outputSize.isNull())
> > +		return Unpopulated;
> > +
> > +	return Invalid;
> > +}
> > +
> >  /**
> >   * \class CameraConfiguration
> >   * \brief Hold configuration for streams of the camera
> > @@ -391,6 +566,16 @@ CameraConfiguration::Status CameraConfiguration::validateColorSpaces(ColorSpaceF
> >  	return status;
> >  }
> >  
> > +/**
> > + * \var CameraConfiguration::sensorConfig
> > + * \brief The camera sensor configuration
> > + *
> > + * The sensorConfig field allows control of the configuration of the camera
> > + * sensor. Refer to the camera-sensor-model documentation and to the
> > + * SensorConfiguration class documentation for details about the sensor
> > + * configuration process.
> > + */
> > +
> >  /**
> >   * \var CameraConfiguration::transform
> >   * \brief User-specified transform to be applied to the image

-- 
Regards,

Laurent Pinchart