libcamera::Request Class Reference

A frame capture request. More...

Inherits Extensible.

Public Types
enum	Status { RequestPending, RequestComplete, RequestCancelled }
enum	ReuseFlag { Default = 0, ReuseBuffers = (1 << 0) }
using	BufferMap = std::map< const Stream *, FrameBuffer * >
	A map of Stream to FrameBuffer pointers.

Public Member Functions
	Request (Camera *camera, uint64_t cookie=0)
	Create a capture request for a camera. More...
void	reuse (ReuseFlag flags=Default)
	Reset the request for reuse. More...
ControlList &	controls ()
	Retrieve the request's ControlList. More...
ControlList &	metadata ()
	Retrieve the request's metadata. More...
const BufferMap &	buffers () const
	Retrieve the request's streams to buffers map. More...
int	addBuffer (const Stream *stream, FrameBuffer *buffer, std::unique_ptr< Fence > fence=nullptr)
	Add a FrameBuffer with its associated Stream to the Request. More...
FrameBuffer *	findBuffer (const Stream *stream) const
	Return the buffer associated with a stream. More...
uint32_t	sequence () const
	Retrieve the sequence number for the request. More...
uint64_t	cookie () const
	Retrieve the cookie set when the request was created. More...
Status	status () const
	Retrieve the request completion status. More...
bool	hasPendingBuffers () const
	Check if a request has buffers yet to be completed. More...
std::string	toString () const
	Generate a string representation of the Request internals. More...

Detailed Description

A frame capture request.

A Request allows an application to associate buffers and controls on a per-frame basis to be queued to the camera device for processing.

Member Enumeration Documentation

ReuseFlag

enum libcamera::Request::ReuseFlag

Flags to control the behavior of Request::reuse()

Enumerator
Default	Don't reuse buffers
ReuseBuffers	Reuse the buffers that were previously added by addBuffer()

Status

enum libcamera::Request::Status

Request completion status

Enumerator
RequestPending	The request hasn't completed yet
RequestComplete	The request has completed
RequestCancelled	The request has been cancelled due to capture stop

Constructor & Destructor Documentation

Request()

libcamera::Request::Request	(	Camera *	camera,
		uint64_t	cookie = 0
	)

Create a capture request for a camera.

Parameters

[in]	camera	The camera that creates the request
[in]	cookie	Opaque cookie for application use

The cookie is stored in the request and is accessible through the cookie() function at any time. It is typically used by applications to map the request to an external resource in the request completion handler, and is completely opaque to libcamera.

Todo:

Add a validator for metadata controls.

Member Function Documentation

addBuffer()

int libcamera::Request::addBuffer	(	const Stream *	stream,
		FrameBuffer *	buffer,
		std::unique_ptr< Fence >	fence = nullptr
	)

Add a FrameBuffer with its associated Stream to the Request.

Parameters

[in]	stream	The stream the buffer belongs to
[in]	buffer	The FrameBuffer to add to the request
[in]	fence	The optional fence

A reference to the buffer is stored in the request. The caller is responsible for ensuring that the buffer will remain valid until the request complete callback is called.

A request can only contain one buffer per stream. If a buffer has already been added to the request for the same stream, this function returns -EEXIST.

A Fence can be optionally associated with the buffer.

When a valid Fence is provided to this function, fence is moved to buffer and this Request will only be queued to the device once the fences of all its buffers have been correctly signalled.

If the fence associated with buffer isn't signalled, the request will fail after a timeout. The buffer will still contain the fence, which applications must retrieve with FrameBuffer::releaseFence() before the buffer can be reused in another request. Attempting to add a buffer that still contains a fence to a request will result in this function returning -EEXIST.

See also

FrameBuffer::releaseFence()

Returns

0 on success or a negative error code otherwise

Return values

-EEXIST	The request already contains a buffer for the stream or the buffer still references a fence
-EINVAL	The buffer does not reference a valid Stream

buffers()

libcamera::Request::buffers ( ) const

inline

Retrieve the request's streams to buffers map.

Return a reference to the map that associates each Stream part of the request to the FrameBuffer the Stream output should be directed to.

Returns

The map of Stream to FrameBuffer

controls()

libcamera::Request::controls ( )

inline

Retrieve the request's ControlList.

Requests store a list of controls to be applied to all frames captured for the request. They are created with an empty list of controls that can be accessed through this function. Control values can be retrieved using ControlList::get() and updated using ControlList::set().

Only controls supported by the camera to which this request will be submitted shall be included in the controls list. Attempting to add an unsupported control causes undefined behaviour.

Returns

A reference to the ControlList in this request

cookie()

libcamera::Request::cookie ( ) const

inline

Retrieve the cookie set when the request was created.

Returns

The request cookie

findBuffer()

FrameBuffer * libcamera::Request::findBuffer

(

const Stream *

stream

)

const

Return the buffer associated with a stream.

Parameters

[in]

stream

The stream the buffer is associated to

Returns

The buffer associated with the stream, or nullptr if the stream is not part of this request

hasPendingBuffers()

bool libcamera::Request::hasPendingBuffers

(

)

const

Check if a request has buffers yet to be completed.

Returns

True if the request has buffers pending for completion, false otherwise

metadata()

libcamera::Request::metadata ( )

inline

Retrieve the request's metadata.

Todo:

Offer a read-only API towards applications while keeping a read/write API internally.

Returns

The metadata associated with the request

reuse()

void libcamera::Request::reuse

(

ReuseFlag

flags = Default

)

Reset the request for reuse.

Parameters

[in]

flags

Indicate whether or not to reuse the buffers

Reset the status and controls associated with the request, to allow it to be reused and requeued without destruction. This function shall be called prior to queueing the request to the camera, in lieu of constructing a new request. The application can reuse the buffers that were previously added to the request via addBuffer() by setting flags to ReuseBuffers.

sequence()

uint32_t libcamera::Request::sequence

(

)

const

Retrieve the sequence number for the request.

When requests are queued, they are given a sequential number to track the order in which requests are queued to a camera. This number counts all requests given to a camera and is reset to zero between camera stop/start sequences.

It can be used to support debugging and identifying the flow of requests through a pipeline, but does not guarantee to represent the sequence number of any images in the stream. The sequence number is stored as an unsigned integer and will wrap when overflowed.

Returns

The request sequence number

status()

libcamera::Request::status ( ) const

inline

Retrieve the request completion status.

The request status indicates whether the request has completed successfully or with an error. When requests are created and before they complete the request status is set to RequestPending, and is updated at completion time to RequestComplete. If a request is cancelled at capture stop before it has completed, its status is set to RequestCancelled.

Returns

The request completion status

toString()

std::string libcamera::Request::toString

(

)

const

Generate a string representation of the Request internals.

This function facilitates debugging of Request state while it is used internally within libcamera.

Returns

A string representing the current state of the request

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The documentation for this class was generated from the following files:

• include/libcamera/request.h
• src/libcamera/request.cpp