[PATCH v3 5/7] Documentation: Remove libcamera architecture from introduction.rst
Daniel Scally
dan.scally at ideasonboard.com
Mon Aug 19 18:09:19 CEST 2024
The libcamera Architecture section of the introduction is largely a
duplicate of the section broken out from docs.rst. Remove it from the
introduction.rst file and consolidate anything that wasn't duplicated
into libcamera_architecture.rst. Take the opportunity to expand the
list of Platform Support which is now a bit out of date.
Signed-off-by: Daniel Scally <dan.scally at ideasonboard.com>
---
Changes since v2:
- Reworked to change libcamera architecture section instead of camera
stack. DDropped R-b
- Updated the list of supported platforms on the new libcamera
architecture page
Changes since v1:
- None
Documentation/guides/introduction.rst | 156 +-------------
Documentation/libcamera_architecture.rst | 261 ++++++++++++-----------
2 files changed, 141 insertions(+), 276 deletions(-)
diff --git a/Documentation/guides/introduction.rst b/Documentation/guides/introduction.rst
index d1e67654..12d1b7d4 100644
--- a/Documentation/guides/introduction.rst
+++ b/Documentation/guides/introduction.rst
@@ -26,10 +26,8 @@ desirable results from the camera.
.. _Media Controller: https://www.linuxtv.org/downloads/v4l-dvb-apis-new/userspace-api/mediactl/media-controller.html
-In this developers guide, we will explore the internal `Architecture`_ of
-the libcamera library with its components. The current `Platform Support`_ is
-detailed, as well as an overview of the `Licensing`_ requirements of the
-project.
+In this developers guide the `Licensing`_ requirements of the project are
+detailed.
This introduction is followed by a walkthrough tutorial to newcomers wishing to
support a new platform with the `Pipeline Handler Writers Guide`_ and for those
@@ -41,156 +39,6 @@ provides a tutorial of the key APIs exposed by libcamera.
.. TODO: Correctly link to the other articles of the guide
-Architecture
-------------
-
-While offering a unified API towards upper layers, and presenting itself as a
-single library, libcamera isn't monolithic. It exposes multiple components
-through its public API and is built around a set of separate helpers internally.
-Hardware abstractions are handled through the use of device-specific components
-where required and dynamically loadable plugins are used to separate image
-processing algorithms from the core libcamera codebase.
-
-::
-
- --------------------------< libcamera Public API >---------------------------
- ^ ^
- | |
- v v
- +-------------+ +---------------------------------------------------+
- | Camera | | Camera Device |
- | Manager | | +-----------------------------------------------+ |
- +-------------+ | | Device-Agnostic | |
- ^ | | | |
- | | | +--------------------------+ |
- | | | | ~~~~~~~~~~~~~~~~~~~~~~~ |
- | | | | { +-----------------+ } |
- | | | | } | //// Image //// | { |
- | | | | <-> | / Processing // | } |
- | | | | } | / Algorithms // | { |
- | | | | { +-----------------+ } |
- | | | | ~~~~~~~~~~~~~~~~~~~~~~~ |
- | | | | ========================== |
- | | | | +-----------------+ |
- | | | | | // Pipeline /// | |
- | | | | <-> | /// Handler /// | |
- | | | | | /////////////// | |
- | | +--------------------+ +-----------------+ |
- | | Device-Specific |
- | +---------------------------------------------------+
- | ^ ^
- | | |
- v v v
- +--------------------------------------------------------------------+
- | Helpers and Support Classes |
- | +-------------+ +-------------+ +-------------+ +-------------+ |
- | | MC & V4L2 | | Buffers | | Sandboxing | | Plugins | |
- | | Support | | Allocator | | IPC | | Manager | |
- | +-------------+ +-------------+ +-------------+ +-------------+ |
- | +-------------+ +-------------+ |
- | | Pipeline | | ... | |
- | | Runner | | | |
- | +-------------+ +-------------+ |
- +--------------------------------------------------------------------+
-
- /// Device-Specific Components
- ~~~ Sandboxing
-
-
-Camera Manager
- The Camera Manager enumerates cameras and instantiates Pipeline Handlers to
- manage each Camera that libcamera supports. The Camera Manager supports
- hotplug detection and notification events when supported by the underlying
- kernel devices.
-
- There is only ever one instance of the Camera Manager running per application.
- Each application's instance of the Camera Manager ensures that only a single
- application can take control of a camera device at once.
-
- Read the `Camera Manager API`_ documentation for more details.
-
-.. _Camera Manager API: https://libcamera.org/api-html/classlibcamera_1_1CameraManager.html
-
-Camera Device
- The Camera class represents a single item of camera hardware that is capable
- of producing one or more image streams, and provides the API to interact with
- the underlying device.
-
- If a system has multiple instances of the same hardware attached, each has its
- own instance of the camera class.
-
- The API exposes full control of the device to upper layers of libcamera through
- the public API, making it the highest level object libcamera exposes, and the
- object that all other API operations interact with from configuration to
- capture.
-
- Read the `Camera API`_ documentation for more details.
-
-.. _Camera API: https://libcamera.org/api-html/classlibcamera_1_1Camera.html
-
-Pipeline Handler
- The Pipeline Handler manages the complex pipelines exposed by the kernel
- drivers through the Media Controller and V4L2 APIs. It abstracts pipeline
- handling to hide device-specific details from the rest of the library, and
- implements both pipeline configuration based on stream configuration, and
- pipeline runtime execution and scheduling when needed by the device.
-
- The Pipeline Handler lives in the same process as the rest of the library, and
- has access to all helpers and kernel camera-related devices.
-
- Hardware abstraction is handled by device specific Pipeline Handlers which are
- derived from the Pipeline Handler base class allowing commonality to be shared
- among the implementations.
-
- Derived pipeline handlers create Camera device instances based on the devices
- they detect and support on the running system, and are responsible for
- managing the interactions with a camera device.
-
- More details can be found in the `PipelineHandler API`_ documentation, and the
- `Pipeline Handler Writers Guide`_.
-
-.. _PipelineHandler API: https://libcamera.org/api-html/classlibcamera_1_1PipelineHandler.html
-
-Image Processing Algorithms
- An image processing algorithm (IPA) component is a loadable plugin that
- implements 3A (Auto-Exposure, Auto-White Balance, and Auto-Focus) and other
- algorithms.
-
- The algorithms run on the CPU and interact with the camera devices through the
- Pipeline Handler to control hardware image processing based on the parameters
- supplied by upper layers, maintaining state and closing the control loop
- of the ISP.
-
- The component is sandboxed and can only interact with libcamera through the
- API provided by the Pipeline Handler and an IPA has no direct access to kernel
- camera devices.
-
- Open source IPA modules built with libcamera can be run in the same process
- space as libcamera, however external IPA modules are run in a separate process
- from the main libcamera process. IPA modules have a restricted view of the
- system, including no access to networking APIs and limited access to file
- systems.
-
- IPA modules are only required for platforms and devices with an ISP controlled
- by the host CPU. Camera sensors which have an integrated ISP are not
- controlled through the IPA module.
-
-Platform Support
-----------------
-
-The library currently supports the following hardware platforms specifically
-with dedicated pipeline handlers:
-
- - Intel IPU3 (ipu3)
- - Rockchip RK3399 (rkisp1)
- - RaspberryPi 3 and 4 (rpi/vc4)
-
-Furthermore, generic platform support is provided for the following:
-
- - USB video device class cameras (uvcvideo)
- - iMX7, Allwinner Sun6i (simple)
- - Virtual media controller driver for test use cases (vimc)
-
Licensing
---------
diff --git a/Documentation/libcamera_architecture.rst b/Documentation/libcamera_architecture.rst
index 1258db23..699a1347 100644
--- a/Documentation/libcamera_architecture.rst
+++ b/Documentation/libcamera_architecture.rst
@@ -5,134 +5,151 @@
libcamera Architecture
======================
+While offering a unified API towards upper layers, and presenting itself as a
+single library, libcamera isn't monolithic. It exposes multiple components
+through its public API and is built around a set of separate helpers internally.
+Hardware abstractions are handled through the use of device-specific components
+where required and dynamically loadable plugins are used to separate image
+processing algorithms from the core libcamera codebase.
+
::
- ---------------------------< libcamera Public API >---------------------------
- ^ ^
- | |
- v v
- +-------------+ +-------------------------------------------------+
- | Camera | | Camera Device |
- | Devices | | +---------------------------------------------+ |
- | Manager | | | Device-Agnostic | |
- +-------------+ | | | |
- ^ | | +------------------------+ |
- | | | | ~~~~~~~~~~~~~~~~~~~~~ |
- | | | | { +---------------+ } |
- | | | | } | ////Image//// | { |
- | | | | <-> | /Processing// | } |
- | | | | } | /Algorithms// | { |
- | | | | { +---------------+ } |
- | | | | ~~~~~~~~~~~~~~~~~~~~~ |
- | | | | ======================== |
- | | | | +---------------+ |
- | | | | | //Pipeline/// | |
- | | | | <-> | ///Handler/// | |
- | | | | | ///////////// | |
- | | +--------------------+ +---------------+ |
- | | Device-Specific |
- | +-------------------------------------------------+
- | ^ ^
- | | |
- v v v
- +--------------------------------------------------------------------+
- | Helpers and Support Classes |
- | +-------------+ +-------------+ +-------------+ +-------------+ |
- | | MC & V4L2 | | Buffers | | Sandboxing | | Plugins | |
- | | Support | | Allocator | | IPC | | Manager | |
- | +-------------+ +-------------+ +-------------+ +-------------+ |
- | +-------------+ +-------------+ |
- | | Pipeline | | ... | |
- | | Runner | | | |
- | +-------------+ +-------------+ |
- +--------------------------------------------------------------------+
-
- /// Device-Specific Components
- ~~~ Sandboxing
-
-While offering a unified API towards upper layers, and presenting
-itself as a single library, libcamera isn't monolithic. It exposes
-multiple components through its public API, is built around a set of
-separate helpers internally, uses device-specific components and can
-load dynamic plugins.
-
-Camera Devices Manager
- The Camera Devices Manager provides a view of available cameras
- in the system. It performs cold enumeration and runtime camera
- management, and supports a hotplug notification mechanism in its
- public API.
-
- To avoid the cost associated with cold enumeration of all devices
- at application start, and to arbitrate concurrent access to camera
- devices, the Camera Devices Manager could later be split to a
- separate service, possibly with integration in platform-specific
- device management.
+ --------------------------< libcamera Public API >---------------------------
+ ^ ^
+ | |
+ v v
+ +-------------+ +---------------------------------------------------+
+ | Camera | | Camera Device |
+ | Manager | | +-----------------------------------------------+ |
+ +-------------+ | | Device-Agnostic | |
+ ^ | | | |
+ | | | +--------------------------+ |
+ | | | | ~~~~~~~~~~~~~~~~~~~~~~~ |
+ | | | | { +-----------------+ } |
+ | | | | } | //// Image //// | { |
+ | | | | <-> | / Processing // | } |
+ | | | | } | / Algorithms // | { |
+ | | | | { +-----------------+ } |
+ | | | | ~~~~~~~~~~~~~~~~~~~~~~~ |
+ | | | | ========================== |
+ | | | | +-----------------+ |
+ | | | | | // Pipeline /// | |
+ | | | | <-> | /// Handler /// | |
+ | | | | | /////////////// | |
+ | | +--------------------+ +-----------------+ |
+ | | Device-Specific |
+ | +---------------------------------------------------+
+ | ^ ^
+ | | |
+ v v v
+ +--------------------------------------------------------------------+
+ | Helpers and Support Classes |
+ | +-------------+ +-------------+ +-------------+ +-------------+ |
+ | | MC & V4L2 | | Buffers | | Sandboxing | | Plugins | |
+ | | Support | | Allocator | | IPC | | Manager | |
+ | +-------------+ +-------------+ +-------------+ +-------------+ |
+ | +-------------+ +-------------+ |
+ | | Pipeline | | ... | |
+ | | Runner | | | |
+ | +-------------+ +-------------+ |
+ +--------------------------------------------------------------------+
+
+ /// Device-Specific Components
+ ~~~ Sandboxing
+
+
+Camera Manager
+ The Camera Manager enumerates cameras and instantiates Pipeline Handlers to
+ manage each Camera that libcamera supports. The Camera Manager supports
+ hotplug detection and notification events when supported by the underlying
+ kernel devices.
+
+ There is only ever one instance of the Camera Manager running per application.
+ Each application's instance of the Camera Manager ensures that only a single
+ application can take control of a camera device at once.
+
+ Read the `Camera Manager API`_ documentation for more details.
+
+.. _Camera Manager API: https://libcamera.org/api-html/classlibcamera_1_1CameraManager.html
Camera Device
- The Camera Device represents a camera device to upper layers. It
- exposes full control of the device through the public API, and is
- thus the highest level object exposed by libcamera.
+ The Camera class represents a single item of camera hardware that is capable
+ of producing one or more image streams, and provides the API to interact with
+ the underlying device.
+
+ If a system has multiple instances of the same hardware attached, each has its
+ own instance of the camera class.
+
+ The API exposes full control of the device to upper layers of libcamera through
+ the public API, making it the highest level object libcamera exposes, and the
+ object that all other API operations interact with from configuration to
+ capture.
- Camera Device instances are created by the Camera Devices
- Manager. An optional function to create new instances could be exposed
- through the public API to speed up initialization when the upper
- layer knows how to directly address camera devices present in the
- system.
+ Read the `Camera API`_ documentation for more details.
+
+.. _Camera API: https://libcamera.org/api-html/classlibcamera_1_1Camera.html
Pipeline Handler
- The Pipeline Handler manages complex pipelines exposed by the kernel drivers
- through the Media Controller and V4L2 APIs. It abstracts pipeline handling to
- hide device-specific details to the rest of the library, and implements both
- pipeline configuration based on stream configuration, and pipeline runtime
- execution and scheduling when needed by the device.
-
- This component is device-specific and is part of the libcamera code base. As
- such it is covered by the same free software license as the rest of libcamera
- and needs to be contributed upstream by device vendors. The Pipeline Handler
- lives in the same process as the rest of the library, and has access to all
- helpers and kernel camera-related devices.
+ The Pipeline Handler manages the complex pipelines exposed by the kernel
+ drivers through the Media Controller and V4L2 APIs. It abstracts pipeline
+ handling to hide device-specific details from the rest of the library, and
+ implements both pipeline configuration based on stream configuration, and
+ pipeline runtime execution and scheduling when needed by the device.
+
+ The Pipeline Handler lives in the same process as the rest of the library, and
+ has access to all helpers and kernel camera-related devices.
+
+ Hardware abstraction is handled by device specific Pipeline Handlers which are
+ derived from the Pipeline Handler base class allowing commonality to be shared
+ among the implementations.
+
+ Derived pipeline handlers create Camera device instances based on the devices
+ they detect and support on the running system, and are responsible for
+ managing the interactions with a camera device.
+
+ More details can be found in the `PipelineHandler API`_ documentation, and the
+ :doc:`Pipeline Handler Writers Guide <guides/pipeline-handler>`.
+
+.. _PipelineHandler API: https://libcamera.org/api-html/classlibcamera_1_1PipelineHandler.html
Image Processing Algorithms
- Together with the hardware image processing and hardware statistics
- collection, the Image Processing Algorithms implement 3A (Auto-Exposure,
- Auto-White Balance and Auto-Focus) and other algorithms. They run on the CPU
- and interact with the kernel camera devices to control hardware image
- processing based on the parameters supplied by upper layers, closing the
- control loop of the ISP.
-
- This component is device-specific and is loaded as an external plugin. It can
- be part of the libcamera code base, in which case it is covered by the same
- license, or provided externally as an open-source or closed-source component.
-
- The component is sandboxed and can only interact with libcamera through
- internal APIs specifically marked as such. In particular it will have no
- direct access to kernel camera devices, and all its accesses to image and
- metadata will be mediated by dmabuf instances explicitly passed to the
- component. The component must be prepared to run in a process separate from
- the main libcamera process, and to have a very restricted view of the system,
- including no access to networking APIs and limited access to file systems.
-
- The sandboxing mechanism isn't defined by libcamera. One example
- implementation will be provided as part of the project, and platforms vendors
- will be able to provide their own sandboxing mechanism as a plugin.
-
- libcamera should provide a basic implementation of Image Processing
- Algorithms, to serve as a reference for the internal API. Device vendors are
- expected to provide a full-fledged implementation compatible with their
- Pipeline Handler. One goal of the libcamera project is to create an
- environment in which the community will be able to compete with the
- closed-source vendor binaries and develop a high quality open source
- implementation.
-
-Helpers and Support Classes
- While Pipeline Handlers are device-specific, implementations are expected to
- share code due to usage of identical APIs towards the kernel camera drivers
- and the Image Processing Algorithms. This includes without limitation handling
- of the MC and V4L2 APIs, buffer management through dmabuf, and pipeline
- discovery, configuration and scheduling. Such code will be factored out to
- helpers when applicable.
-
- Other parts of libcamera will also benefit from factoring code out to
- self-contained support classes, even if such code is present only once in the
- code base, in order to keep the source code clean and easy to read. This
- should be the case for instance for plugin management.
+ An image processing algorithm (IPA) component is a loadable plugin that
+ implements 3A (Auto-Exposure, Auto-White Balance, and Auto-Focus) and other
+ algorithms.
+
+ The algorithms run on the CPU and interact with the camera devices through the
+ Pipeline Handler to control hardware image processing based on the parameters
+ supplied by upper layers, maintaining state and closing the control loop
+ of the ISP.
+
+ The component is sandboxed and can only interact with libcamera through the
+ API provided by the Pipeline Handler and an IPA has no direct access to kernel
+ camera devices.
+
+ Open source IPA modules built with libcamera can be run in the same process
+ space as libcamera, however external IPA modules are run in a separate process
+ from the main libcamera process. IPA modules have a restricted view of the
+ system, including no access to networking APIs and limited access to file
+ systems.
+
+ IPA modules are only required for platforms and devices with an ISP controlled
+ by the host CPU. Camera sensors which have an integrated ISP are not
+ controlled through the IPA module.
+
+Platform Support
+----------------
+
+The library currently supports the following hardware platforms specifically
+with dedicated pipeline handlers:
+
+ - Arm Mali-C55
+ - Intel IPU3 (ipu3)
+ - NXP i.MX8MP (imx8-isi and rkisp1)
+ - Rockchip RK3399 (rkisp1)
+ - RaspberryPi 3, 4 and zero (rpi/vc4)
+
+Furthermore, generic platform support is provided for the following:
+
+ - USB video device class cameras (uvcvideo)
+ - iMX7, IPU6, Allwinner Sun6i (simple)
+ - Virtual media controller driver for test use cases (vimc)
--
2.34.1
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