libcamera::Fence Class Reference

Synchronization primitive to manage resources. More...

Public Member Functions
	Fence (UniqueFD fd)
	Create a Fence. More...
bool	isValid () const
	Check if a Fence is valid. More...
const UniqueFD &	fd () const
	Retrieve a constant reference to the file descriptor. More...
UniqueFD	release ()
	Release the ownership of the file descriptor. More...

Detailed Description

Synchronization primitive to manage resources.

The Fence class models a synchronization primitive that can be used by applications to explicitly synchronize resource usage, and can be shared by multiple processes.

Fences are most commonly used in association with frame buffers. A FrameBuffer can be associated with a Fence so that the library can wait for the Fence to be signalled before allowing the camera device to actually access the memory area described by the FrameBuffer.

See also

Request::addBuffer()

By using a fence, applications can then synchronize between frame buffer consumers and producers, as for example a display device and a camera, to guarantee that a new data transfers only happen once the existing frames have been displayed.

A Fence can be realized by different event notification primitives, the most common of which is represented by waiting for read events to happen on a kernel sync file. This is currently the only mechanism supported by libcamera, but others can be implemented by extending or subclassing this class and implementing opportune handling in the core library.

Constructor & Destructor Documentation

Fence()

libcamera::Fence::Fence

(

UniqueFD

fd

)

Create a Fence.

Parameters

[in]

fd

The fence file descriptor

The file descriptor ownership is moved to the Fence.

Member Function Documentation

fd()

libcamera::Fence::fd ( ) const

inline

Retrieve a constant reference to the file descriptor.

Returns

A const reference to the fence file descriptor

isValid()

libcamera::Fence::isValid ( ) const

inline

Check if a Fence is valid.

A Fence is valid if the file descriptor it wraps is valid.

Returns

True if the Fence is valid, false otherwise

release()

libcamera::Fence::release ( )

inline

Release the ownership of the file descriptor.

Release the ownership of the wrapped file descriptor by returning it to the caller.

Returns

The wrapper UniqueFD

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

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