From patchwork Fri Aug 9 14:53:00 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dan Scally X-Patchwork-Id: 20864 Return-Path: X-Original-To: parsemail@patchwork.libcamera.org Delivered-To: parsemail@patchwork.libcamera.org Received: from lancelot.ideasonboard.com (lancelot.ideasonboard.com [92.243.16.209]) by patchwork.libcamera.org (Postfix) with ESMTPS id 40BD3C323E for ; Fri, 9 Aug 2024 14:53:29 +0000 (UTC) Received: from lancelot.ideasonboard.com (localhost [IPv6:::1]) by lancelot.ideasonboard.com (Postfix) with ESMTP id BD5C2633BF; Fri, 9 Aug 2024 16:53:28 +0200 (CEST) Authentication-Results: lancelot.ideasonboard.com; dkim=pass (1024-bit key; unprotected) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="Jfesmh25"; dkim-atps=neutral Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647]) by lancelot.ideasonboard.com (Postfix) with ESMTPS id 8C429633B3 for ; Fri, 9 Aug 2024 16:53:20 +0200 (CEST) Received: from mail.ideasonboard.com (cpc141996-chfd3-2-0-cust928.12-3.cable.virginm.net [86.13.91.161]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 3C73DA38; Fri, 9 Aug 2024 16:52:26 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1723215146; bh=9JagfBZs5bFQ/6IPp2pagx1tx+2N+cPMmNXOdX0cFhA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Jfesmh25W+7eKQnTltMDS/gCr0lV0zfF36yO6Z0gB6Z/LCdGUtq6JDojdYXUgSiif ZEkxiHSRI3ZNr0tnKKYkwoptSmOCsJNt/W3/TFCdaxSFKddMA9Zbj5oOs+7BKW9ZQf Io46fa2PVF3ygK28ZRXyH8oVCO0MiIlyudhHCrII= From: Daniel Scally To: libcamera-devel@lists.libcamera.org Cc: Daniel Scally Subject: [PATCH 3/7] Documentation: Synchronise libcamera architecture details Date: Fri, 9 Aug 2024 15:53:00 +0100 Message-Id: <20240809145304.537551-4-dan.scally@ideasonboard.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240809145304.537551-1-dan.scally@ideasonboard.com> References: <20240809145304.537551-1-dan.scally@ideasonboard.com> MIME-Version: 1.0 X-BeenThere: libcamera-devel@lists.libcamera.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libcamera-devel-bounces@lists.libcamera.org Sender: "libcamera-devel" There are two near-duplicate instances of the libcamera architecture detail in the Documentation, in docs.rst and guides/introduction.rst. The latter is more up-to-date, so remove it from the introduction file (which will soon be deprecated) and update the section in docs. Signed-off-by: Daniel Scally Reviewed-by: Laurent Pinchart --- Documentation/docs.rst | 221 ++++++++++++++------------ Documentation/guides/introduction.rst | 137 +--------------- 2 files changed, 121 insertions(+), 237 deletions(-) diff --git a/Documentation/docs.rst b/Documentation/docs.rst index 5871961c..10f07a9e 100644 --- a/Documentation/docs.rst +++ b/Documentation/docs.rst @@ -243,116 +243,135 @@ The camera stack comprises four software layers. From bottom to top: 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 `. + +.. _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. + 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. libcamera should provide a basic implementation of Image Processing Algorithms, to serve as a reference for the internal API. Device vendors are diff --git a/Documentation/guides/introduction.rst b/Documentation/guides/introduction.rst index 8368bd4a..1898d5fe 100644 --- a/Documentation/guides/introduction.rst +++ b/Documentation/guides/introduction.rst @@ -27,8 +27,7 @@ desirable results from the camera. In this developers guide, we will explore the `Camera Stack`_ and how it is -can be visualised at a high level, and explore the internal `Architecture`_ of -the libcamera library with its components. The current `Platform Support`_ is +can be visualised at a high level. The current `Platform Support`_ is detailed, as well as an overview of the `Licensing`_ requirements of the project. @@ -148,140 +147,6 @@ Native libcamera API .. _GStreamer element: https://gstreamer.freedesktop.org/documentation/application-development/basics/elements.html -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 ----------------