libcamera  v0.3.2+188-9fc86dc0
Supporting cameras in Linux since 2019
Public Types | Public Member Functions | List of all members
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...
 
ControlListcontrols ()
 Retrieve the request's ControlList. More...
 
ControlListmetadata ()
 Retrieve the request's metadata. More...
 
const BufferMapbuffers () 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...
 
FrameBufferfindBuffer (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

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

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]cameraThe camera that creates the request
[in]cookieOpaque 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]streamThe stream the buffer belongs to
[in]bufferThe FrameBuffer to add to the request
[in]fenceThe 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
-EEXISTThe request already contains a buffer for the stream or the buffer still references a fence
-EINVALThe 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]streamThe 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]flagsIndicate 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

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