[libcamera-devel] [PATCH v4 6/6] libcamera: camera: extend camera object to support configuration of streams

[Kieran Bingham]

Hi Niklas,

On 29/01/2019 02:00, Niklas Söderlund wrote:
> Extend the camera to support reading and configuring formats for
> groups of streams. The implementation in the Camera are minimalistic as
> the heavy lifting are done by the pipeline handler implementations.
> 
> The most important functionality the camera provides in this context is
> validation of data structures passed to it from the application and
> access control to the pipeline handler.
> 
> Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> ---
>  include/libcamera/camera.h |  4 +++
>  src/libcamera/camera.cpp   | 61 ++++++++++++++++++++++++++++++++++++++
>  2 files changed, 65 insertions(+)
> 
> diff --git a/include/libcamera/camera.h b/include/libcamera/camera.h
> index 3ebb8e96cc63b98a..7a0357f3a2919752 100644
> --- a/include/libcamera/camera.h
> +++ b/include/libcamera/camera.h
> @@ -7,6 +7,7 @@
>  #ifndef __LIBCAMERA_CAMERA_H__
>  #define __LIBCAMERA_CAMERA_H__
>  
> +#include <map>
>  #include <memory>
>  #include <string>
>  
> @@ -16,6 +17,7 @@ namespace libcamera {
>  
>  class PipelineHandler;
>  class Stream;
> +class StreamConfiguration;
>  
>  class Camera final
>  {
> @@ -35,6 +37,8 @@ public:
>  	void release();
>  
>  	std::vector<Stream *> streams() const;
> +	std::map<Stream*, StreamConfiguration> streamConfiguration(std::vector<Stream*> &streams);
> +	int configureStreams(std::map<Stream*, StreamConfiguration> &config);
>  
>  private:
>  	Camera(PipelineHandler *pipe, const std::string &name);
> diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
> index c8604ec8a8e6eaf4..69d28a10f1f73d0d 100644
> --- a/src/libcamera/camera.cpp
> +++ b/src/libcamera/camera.cpp
> @@ -190,4 +190,65 @@ std::vector<Stream *> Camera::streams() const
>  	return streams_;
>  }
>  
> +/**
> + * \brief Retrieve a group of stream configurations
> + * \param[in] streams A map of stream IDs and configurations to setup
> + *
> + * Retrieve the camera's configuration for a specified group of streams. The
> + * caller can specifies which of the camera's streams to retrieve configuration
> + * from by populating \a streams.
> + *
> + * The easiest way to populate the array of streams to fetch configuration from
> + * is to first retrieve the camera's full array of stream by with streams() and
> + * then potentially trim it down to only contain the streams the caller
> + * are interested in.
> + *
> + * \return A map of successfully retrieved stream IDs and configurations or an
> + * empty list on error.
> + */
> +std::map<Stream*, StreamConfiguration>
> +Camera::streamConfiguration(std::vector<Stream*> &streams)
> +{
> +	if (disconnected_ || !streams.size())
> +		std::map<unsigned int, StreamConfiguration>{};
> +
> +	return pipe_->streamConfiguration(this, streams);
> +}
> +
> +/**
> + * \brief Configure the camera's streams prior to capture
> + * \param[in] config A map of stream IDs and configurations to setup
> + *
> + * Prior to starting capture, the camera must be configured to select a
> + * group of streams to be involved in the capture and their configuration.
> + * The caller specifies which streams are to be involved and their configuration
> + * by populating \a config.
> + *
> + * The easiest way to populate the array of config is to fetch an initial
> + * configuration from the camera with streamConfiguration() and then change the
> + * parameters to fit the caller's need and once all the streams parameters are
> + * configured hand that over to configureStreams() to actually setup the camera.
> + *
> + * Exclusive access to the camera shall be ensured by a call to acquire() prior
> + * to calling this function, otherwise an -EACCES error is be returned.
> + *
> + * \return 0 on success or a negative error code on error.
> + * \retval -ENODEV The camera is not connected to any hardware
> + * \retval -EACCES The user have not acquired exclusive access to the camera
> + * \retval -EINVAL The configuration is not valid
> + */
> +int Camera::configureStreams(std::map<Stream*, StreamConfiguration> &config)
> +{
> +	if (disconnected_)
> +		return -ENODEV;
> +
> +	if (!acquired_)
> +		return -EACCES;
> +
> +	if (!config.size())
> +		return -EINVAL;
> +

Perhaps not necessary in this patch - but it looks like perhaps we
should wrap the access control into a function.

It's going to be required for almost every call through the Camera
object, and it might need flags to determine what control is allowed.

int CameraAccessAllowed(AccessFlags)
{
  if (disconnected_)
	return -ENODEV;

  if ( (AccessFlags & MUST_ACQUIRE) && !acquired )
	return -EACCES;

  /* Other checks / flags here ? */

  return true;
}

Camera::configureStreams(std::map<Stream*, StreamConfiguration> &config)
{

  int ret = CameraAccessAllowed(MUST_ACQUIRE | MUST_EXIST)
  if (ret)
	return ret;

  if (!config.size())
	return -EINVAL;
  ...
}

Then this :
> \retval -ENODEV The camera is not connected to any hardware
> \retval -EACCES The user have not acquired exclusive access to the camera
> \retval -EINVAL The configuration is not valid

can be documented just once, instead of on every API call.


> +	return pipe_->configureStreams(this, config);
> +}
> +
>  } /* namespace libcamera */
> 

-- 
Regards
--
Kieran