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{ "id": 9339, "url": "https://patchwork.libcamera.org/api/patches/9339/?format=api", "web_url": "https://patchwork.libcamera.org/patch/9339/", "project": { "id": 1, "url": "https://patchwork.libcamera.org/api/projects/1/?format=api", "name": "libcamera", "link_name": "libcamera", "list_id": "libcamera_core", "list_email": "libcamera-devel@lists.libcamera.org", "web_url": "", "scm_url": "", "webscm_url": "" }, "msgid": "<20200820134751.278033-3-kieran.bingham@ideasonboard.com>", "date": "2020-08-20T13:47:50", "name": "[libcamera-devel,v4,2/3] Documentation: Guides: Pipeline Handler Writers Guide", "commit_ref": null, "pull_url": null, "state": "superseded", "archived": false, "hash": "b5e64a4c28d15d7ddeb151be423e091cbe6d616d", "submitter": { "id": 4, "url": "https://patchwork.libcamera.org/api/people/4/?format=api", "name": "Kieran Bingham", "email": "kieran.bingham@ideasonboard.com" }, "delegate": null, "mbox": "https://patchwork.libcamera.org/patch/9339/mbox/", "series": [ { "id": 1225, "url": "https://patchwork.libcamera.org/api/series/1225/?format=api", "web_url": "https://patchwork.libcamera.org/project/libcamera/list/?series=1225", "date": "2020-08-20T13:47:48", "name": "Developer Guides", "version": 4, "mbox": "https://patchwork.libcamera.org/series/1225/mbox/" } ], "comments": "https://patchwork.libcamera.org/api/patches/9339/comments/", "check": "pending", "checks": "https://patchwork.libcamera.org/api/patches/9339/checks/", "tags": {}, "headers": { "Return-Path": "<libcamera-devel-bounces@lists.libcamera.org>", "X-Original-To": "parsemail@patchwork.libcamera.org", "Delivered-To": "parsemail@patchwork.libcamera.org", "Received": [ "from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 5D204BE173\n\tfor <parsemail@patchwork.libcamera.org>;\n\tThu, 20 Aug 2020 13:48:01 +0000 (UTC)", "from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 2954162082;\n\tThu, 20 Aug 2020 15:48:01 +0200 (CEST)", "from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id AA04260381\n\tfor <libcamera-devel@lists.libcamera.org>;\n\tThu, 20 Aug 2020 15:47:57 +0200 (CEST)", "from Q.local (cpc89244-aztw30-2-0-cust3082.18-1.cable.virginm.net\n\t[86.31.172.11])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 291C0A17;\n\tThu, 20 Aug 2020 15:47:57 +0200 (CEST)" ], "Authentication-Results": "lancelot.ideasonboard.com;\n\tdkim=fail reason=\"signature verification failed\" (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"id96eGC7\"; dkim-atps=neutral", "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1597931277;\n\tbh=GWvDPfPUk+SUcze+ekmyZ9u+5COtFbSDxJz9Hn7HBmg=;\n\th=From:To:Cc:Subject:Date:In-Reply-To:References:From;\n\tb=id96eGC7/uDeTkcGaAeKa3jkp+AfrKR5nDbtcikgIE2Zabv1CgiJ8e4nIBdHSdFCq\n\t5N6fgDVO2S+QzzkMGszEra5QPx/1Ii2PFJGLiv7lB2ce9fd2ef/n9w0LFqlMKS9Rww\n\tFyM1xes6LBcw3g0dnLsKRmplnFFYdRYDkOzUddIY=", "From": "Kieran Bingham <kieran.bingham@ideasonboard.com>", "To": "libcamera devel <libcamera-devel@lists.libcamera.org>,\n\tChris Ward <chris@gregariousmammal.com>, Jacopo Mondi <jacopo@jmondi.org>", "Date": "Thu, 20 Aug 2020 14:47:50 +0100", "Message-Id": "<20200820134751.278033-3-kieran.bingham@ideasonboard.com>", "X-Mailer": "git-send-email 2.25.1", "In-Reply-To": "<20200820134751.278033-1-kieran.bingham@ideasonboard.com>", "References": "<20200820134751.278033-1-kieran.bingham@ideasonboard.com>", "MIME-Version": "1.0", "Subject": "[libcamera-devel] [PATCH v4 2/3] Documentation: Guides: Pipeline\n\tHandler Writers Guide", "X-BeenThere": "libcamera-devel@lists.libcamera.org", "X-Mailman-Version": "2.1.29", "Precedence": "list", "List-Id": "<libcamera-devel.lists.libcamera.org>", "List-Unsubscribe": "<https://lists.libcamera.org/options/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=unsubscribe>", "List-Archive": "<https://lists.libcamera.org/pipermail/libcamera-devel/>", "List-Post": "<mailto:libcamera-devel@lists.libcamera.org>", "List-Help": "<mailto:libcamera-devel-request@lists.libcamera.org?subject=help>", "List-Subscribe": "<https://lists.libcamera.org/listinfo/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=subscribe>", "Content-Type": "text/plain; charset=\"utf-8\"", "Content-Transfer-Encoding": "base64", "Errors-To": "libcamera-devel-bounces@lists.libcamera.org", "Sender": "\"libcamera-devel\" <libcamera-devel-bounces@lists.libcamera.org>" }, "content": "From: Chris Chinchilla <chris@gregariousmammal.com>\n\nIntroduce a pipeline-handler writers guide to provide a walk through of\nthe steps and concepts required to implement a new Pipeline Handler.\n\nSigned-off-by: Chris Chinchilla <chris@gregariousmammal.com>\n[Reflow/Rework, update to mainline API]\nSigned-off-by: Jacopo Mondi <jacopo@jmondi.org>\n[Further reworks and review]\nSigned-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>\n---\n Documentation/guides/pipeline-handler.rst | 1473 +++++++++++++++++++++\n Documentation/index.rst | 1 +\n Documentation/meson.build | 1 +\n 3 files changed, 1475 insertions(+)\n create mode 100644 Documentation/guides/pipeline-handler.rst", "diff": "diff --git a/Documentation/guides/pipeline-handler.rst b/Documentation/guides/pipeline-handler.rst\nnew file mode 100644\nindex 000000000000..eb795dcc35b6\n--- /dev/null\n+++ b/Documentation/guides/pipeline-handler.rst\n@@ -0,0 +1,1473 @@\n+.. SPDX-License-Identifier: CC-BY-SA-4.0\n+\n+Pipeline Handler Writers Guide\n+==============================\n+\n+Pipeline handlers are the abstraction layer for device-specific hardware\n+configuration. They access and control hardware through the V4L2 and Media\n+Controller kernel interfaces, and implement an internal API to control the ISP\n+and capture components of a pipeline directly.\n+\n+Prerequisite knowledge: system architecture\n+-------------------------------------------\n+\n+A pipeline handler configures and manages the image acquisition and\n+transformation pipeline realized by specialized system peripherals combined with\n+an image source connected to the system through a data and control bus. The\n+presence, number and characteristics of them vary depending on the system design\n+and the product integration of the target platform.\n+\n+System components can be classified in three macro-categories:\n+\n+.. TODO: Insert references to the open CSI-2 (and other) specification.\n+\n+- Input ports: Interfaces to external devices, usually image sensors,\n+ which transfer data from the physical bus to locations accessible by other\n+ system peripherals. An input port needs to be configured according to the\n+ input image format and size and could optionally apply basic transformations\n+ on the received images, most typically cropping/scaling and some formats\n+ conversion. The industry standard for the system typically targeted by\n+ libcamera is to have receivers compliant with the MIPI CSI-2 specifications,\n+ implemented on a compatible physical layer such as MIPI D-PHY or MIPI C-PHY.\n+ Other design are possible but less common, such as LVDS or the legacy BT.601\n+ and BT.656 parallel protocols.\n+\n+- Image Signal Processor (ISP): A specialized media processor which applies\n+ digital transformations on image streams. ISPs can be integrated as part of\n+ the SoC as a memory interfaced system peripheral or packaged as stand-alone\n+ chips connected to the application processor through a bus. Most hardware used\n+ by libcamera makes use of in-system ISP designs but pipelines can equally\n+ support external ISP chips or be instrumented to use other system resources\n+ such as a GPU or an FPGA IP block. ISPs expose a software programming\n+ interface that allows the configuration of multiple processing blocks which\n+ form an \"Image Transformation Pipeline\". An ISP usually produces 'processed'\n+ image streams along with the metadata describing the processing steps which\n+ have been applied to generate the output frames.\n+\n+- Camera Sensor: Digital components that integrate an image sensor with control\n+ electronics and usually a lens. It interfaces to the SoC image receiver ports\n+ and is programmed to produce images in a format and size suitable for the\n+ current system configuration. Complex camera modules can integrate on-board\n+ ISP or DSP chips and process images before delivering them to the system. Most\n+ systems with a dedicated ISP processor will usually integrate camera sensors\n+ which produce images in Raw Bayer format and defer processing to it.\n+\n+It is the responsibility of the pipeline handler to interface with these (and\n+possibly other) components of the system and implement the following\n+functionalities:\n+\n+- Detect and register camera devices available in the system with an associated\n+ set of image streams.\n+\n+- Configure the image acquisition and processing pipeline by assigning the\n+ system resources (memory, shared components, etc.) to satisfy the\n+ configuration requested by the application.\n+\n+- Start and the stop the image acquisition and processing sessions.\n+\n+- Apply configuration settings requested by applications and computed by image\n+ processing algorithms integrated in libcamera to the hardware devices.\n+\n+- Notify applications of the availability of new images and deliver them to the\n+ correct locations.\n+\n+Prerequisite knowledge: libcamera architecture\n+----------------------------------------------\n+\n+A pipeline handler makes use of the following libcamera classes to realize the\n+functionalities descibed above. Below is a brief overview of each of those:\n+\n+.. TODO: (All) Convert to sphinx refs\n+.. TODO: (MediaDevice) Reference to the Media Device API (possibly with versioning requirements)\n+.. TODO: (IPAInterface) refer to the IPA guide\n+\n+- `MediaDevice <http://libcamera.org/api-html/classlibcamera_1_1MediaDevice.html>`_:\n+ Instances of this class are associated with a kernel media controller\n+ device and its connected objects.\n+\n+- `DeviceEnumerator <http://libcamera.org/api-html/classlibcamera_1_1DeviceEnumerator.html>`_:\n+ Enumerates all media devices attached to the system and the media entities\n+ registered with it, by creating instances of the ``MediaDevice`` class and\n+ storing them.\n+\n+- `DeviceMatch <http://libcamera.org/api-html/classlibcamera_1_1DeviceMatch.html>`_:\n+ Describes a media device search pattern using entity names, or other\n+ properties.\n+\n+- `V4L2VideoDevice <http://libcamera.org/api-html/classlibcamera_1_1V4L2VideoDevice.html>`_:\n+ Models an instance of a V4L2 video device constructed with the path to a V4L2\n+ video device node.\n+\n+- `V4L2SubDevice <http://libcamera.org/api-html/classlibcamera_1_1V4L2Subdevice.html>`_:\n+ Provides an API to the sub-devices that model the hardware components of a\n+ V4L2 device.\n+\n+- `CameraSensor <http://libcamera.org/api-html/classlibcamera_1_1CameraSensor.html>`_:\n+ Abstracts camera sensor handling by hiding the details of the V4L2 subdevice\n+ kernel API and caching sensor information.\n+\n+- `CameraData <http://libcamera.org/api-html/classlibcamera_1_1CameraData.html>`_:\n+ Represents device-specific data a pipeline handler associates to each Camera\n+ instance.\n+\n+- `StreamConfiguration <http://libcamera.org/api-html/structlibcamera_1_1StreamConfiguration.html>`_:\n+ Models the current configuration of an image stream produced by the camera by\n+ reporting its format and sizes.\n+\n+- `CameraConfiguration <http://libcamera.org/api-html/classlibcamera_1_1CameraConfiguration.html>`_:\n+ Represents the current configuration of a camera, which includes a list of\n+ stream configurations for each active stream in a capture session. When\n+ validated, it is applied to the camera.\n+\n+- `IPAInterface <http://libcamera.org/api-html/classlibcamera_1_1IPAInterface.html>`_:\n+ The interface to the Image Processing Algorithm (IPA) module which performs\n+ the computation of the image processing pipeline tuning parameters.\n+\n+- `ControlList <http://libcamera.org/api-html/classlibcamera_1_1ControlList.html>`_:\n+ A list of control items, indexed by Control<> instances or by numerical index\n+ which contains values used by application and IPA to change parameters of\n+ image streams, used to return to applications and share with IPA the metadata\n+ associated with the captured images, and to advertise the immutable camera\n+ characteristics enumerated at system initialization time.\n+\n+Creating a PipelineHandler\n+--------------------------\n+\n+This guide walks through the steps to create a simple pipeline handler\n+called “Vivid” that supports the `V4L2 Virtual Video Test Driver`_ (vivid).\n+\n+To use the vivid test driver, you first need to check that the vivid kernel\n+module is loaded, for example with the ``modprobe vivid`` command.\n+\n+.. _V4L2 Virtual Video Test Driver: https://www.kernel.org/doc/html/latest/admin-guide/media/vivid.html\n+\n+Create the skeleton file structure\n+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n+\n+To add a new pipeline handler, create a directory to hold the pipeline code in\n+the *src/libcamera/pipeline/* directory that matches the name of the pipeline\n+(in this case *vivid*). Inside the new directory add a *meson.build* file that\n+integrates with the libcamera build system, and a *vivid.cpp* file that matches\n+the name of the pipeline.\n+\n+In the *meson.build* file, add the *vivid.cpp* file as a build source for\n+libcamera by adding it to the global meson ``libcamera_sources`` variable:\n+\n+.. code-block:: none\n+\n+ # SPDX-License-Identifier: CC0-1.0\n+\n+ libcamera_sources += files([\n+ 'vivid.cpp',\n+ ])\n+\n+Users of libcamera can selectively enable pipelines while building libcamera\n+using the ``pipelines`` option.\n+\n+For example, to enable only the IPU3, UVC, and VIVID pipelines, specify them as\n+a comma separated list with ``-Dpipelines`` when generating a build directory:\n+\n+.. code-block:: shell\n+\n+ meson build -Dpipelines=ipu3,uvcvideo,vivid\n+\n+Read the `Meson build configuration`_ documentation for more information on\n+configuring a build directory.\n+\n+.. _Meson build configuration: https://mesonbuild.com/Configuring-a-build-directory.html\n+\n+To add the new pipeline handler to this list of options, add its directory name\n+to the libcamera build options in the top level _meson_options.txt_.\n+\n+.. code-block:: none\n+\n+ option('pipelines',\n+ type : 'array',\n+ choices : ['ipu3', 'raspberrypi', 'rkisp1', 'simple', 'uvcvideo', 'vimc', 'vivid'],\n+ description : 'Select which pipeline handlers to include')\n+\n+\n+In *vivid.cpp* add the pipeline handler to the ``libcamera`` namespace, defining\n+a `PipelineHandler`_ derived class named PipelineHandlerVivid, and add stub\n+methods for the overridden class members.\n+\n+.. _PipelineHandler: http://libcamera.org/api-html/classlibcamera_1_1PipelineHandler.html\n+\n+.. code-block:: cpp\n+\n+ namespace libcamera {\n+\n+ class PipelineHandlerVivid : public PipelineHandler\n+ {\n+ public:\n+ PipelineHandlerVivid(CameraManager *manager);\n+\n+ CameraConfiguration *generateConfiguration(Camera *camera,\n+ const StreamRoles &roles) override;\n+ int configure(Camera *camera, CameraConfiguration *config) override;\n+\n+ int exportFrameBuffers(Camera *camera, Stream *stream,\n+ std::vector<std::unique_ptr<FrameBuffer>> *buffers) override;\n+\n+ int start(Camera *camera) override;\n+ void stop(Camera *camera) override;\n+\n+ int queueRequestDevice(Camera *camera, Request *request) override;\n+\n+ bool match(DeviceEnumerator *enumerator) override;\n+ };\n+\n+ PipelineHandlerVivid::PipelineHandlerVivid(CameraManager *manager)\n+ : PipelineHandler(manager)\n+ {\n+ }\n+\n+ CameraConfiguration *PipelineHandlerVivid::generateConfiguration(Camera *camera,\n+ const StreamRoles &roles)\n+ {\n+ return nullptr;\n+ }\n+\n+ int PipelineHandlerVivid::configure(Camera *camera, CameraConfiguration *config)\n+ {\n+ return -1;\n+ }\n+\n+ int PipelineHandlerVivid::exportFrameBuffers(Camera *camera, Stream *stream,\n+ std::vector<std::unique_ptr<FrameBuffer>> *buffers)\n+ {\n+ return -1;\n+ }\n+\n+ int PipelineHandlerVivid::start(Camera *camera)\n+ {\n+ return -1;\n+ }\n+\n+ void PipelineHandlerVivid::stop(Camera *camera)\n+ {\n+ }\n+\n+ int PipelineHandlerVivid::queueRequestDevice(Camera *camera, Request *request)\n+ {\n+ return -1;\n+ }\n+\n+ bool PipelineHandlerVivid::match(DeviceEnumerator *enumerator)\n+ {\n+ return false;\n+ }\n+\n+ REGISTER_PIPELINE_HANDLER(PipelineHandlerVivid);\n+\n+ } /* namespace libcamera */\n+\n+Note that you must register the ``PipelineHandler`` subclass with the pipeline\n+handler factory using the `REGISTER_PIPELINE_HANDLER`_ macro which\n+registers it and creates a global symbol to reference the class and make it\n+available to try and match devices.\n+\n+.. _REGISTER_PIPELINE_HANDLER: http://libcamera.org/api-html/pipeline__handler_8h.html\n+\n+For debugging and testing a pipeline handler during development, you can define\n+a log message category for the pipeline handler. The ``LOG_DEFINE_CATEGORY``\n+macro and ``LIBCAMERA_LOG_LEVELS`` environment variable help you use the inbuilt\n+libcamera `logging infrastructure`_ that allow for the inspection of internal\n+operations in a user-configurable way.\n+\n+.. _logging infrastructure: http://libcamera.org/api-html/log_8h.html\n+\n+Add the following before the ``PipelineHandlerVivid`` class declaration:\n+\n+.. code-block:: cpp\n+\n+ LOG_DEFINE_CATEGORY(VIVID)\n+\n+At this point you need the following includes for logging and pipeline handler\n+features:\n+\n+.. code-block:: cpp\n+\n+ #include \"libcamera/internal/log.h\"\n+ #include \"libcamera/internal/pipeline_handler.h\"\n+\n+Run the following commands:\n+\n+.. code-block:: shell\n+\n+ meson build\n+ ninja -C build\n+\n+To build the libcamera code base, and confirm that the build system found the\n+new pipeline handler by running:\n+\n+.. code-block:: shell\n+\n+ LIBCAMERA_LOG_LEVELS=Pipeline:0 ./build/src/cam/cam -l\n+\n+And you should see output like the below:\n+\n+.. code-block:: shell\n+\n+ DEBUG Pipeline pipeline_handler.cpp:680 Registered pipeline handler \"PipelineHandlerVivid\"\n+\n+Matching devices\n+~~~~~~~~~~~~~~~~\n+\n+Each pipeline handler registered in libcamera gets tested against the current\n+system configuration, by matching a ``DeviceMatch`` with the system\n+``DeviceEnumerator``. A successful match makes sure all the requested components\n+have been registered in the system and allows the pipeline handler to be\n+initialized.\n+\n+The main entry point of a pipeline handler is the `match()`_ class member\n+function. When the ``CameraManager`` is started (using the `start()`_ method),\n+all the registered pipeline handlers are iterated and their ``match`` function\n+called with an enumerator of all devices it found on a system.\n+\n+The match method should identify if there are suitable devices available in the\n+``DeviceEnumerator`` which the pipeline supports, returning ``true`` if it\n+matches a device, and ``false`` if it does not. To do this, construct a\n+`DeviceMatch`_ class with the name of the ``MediaController`` device to match.\n+You can specify the search further by adding specific media entities to the\n+search using the ``.add()`` method on the DeviceMatch.\n+\n+.. _match(): https://www.libcamera.org/api-html/classlibcamera_1_1PipelineHandler.html#a7cd5b652a2414b543ec20ba9dabf61b6\n+.. _start(): http://libcamera.org/api-html/classlibcamera_1_1CameraManager.html#a49e322880a2a26013bb0076788b298c5\n+.. _DeviceMatch: http://libcamera.org/api-html/classlibcamera_1_1DeviceMatch.html\n+\n+This example uses search patterns that match vivid, but when developing a new\n+pipeline handler, you should change this value to suit your device identifier.\n+\n+Replace the contents of the ``PipelineHandlerVivid::match`` method with the\n+following:\n+\n+.. code-block:: cpp\n+\n+ DeviceMatch dm(\"vivid\");\n+ dm.add(\"vivid-000-vid-cap\");\n+ return false; // Prevent infinite loops for now\n+\n+With the device matching criteria defined, attempt to acquire exclusive access\n+to the matching media controller device with the `acquireMediaDevice`_ method.\n+If the method attempts to acquire a device it has already matched, it returns\n+``false``.\n+\n+.. _acquireMediaDevice: http://libcamera.org/api-html/classlibcamera_1_1PipelineHandler.html#a77e424fe704e7b26094164b9189e0f84\n+\n+Add the following below ``dm.add(\"vivid-000-vid-cap\");``:\n+\n+.. code-block:: cpp\n+\n+ MediaDevice *media = acquireMediaDevice(enumerator, dm);\n+ if (!media)\n+ return false;\n+\n+The pipeline handler now needs an additional include. Add the following to the\n+existing include block for device enumeration functionality:\n+\n+.. code-block:: cpp\n+\n+ #include \"libcamera/internal/device_enumerator.h\"\n+\n+At this stage, you should test that the pipeline handler can successfully match\n+the devices, but have not yet added any code to create a Camera which libcamera\n+reports to applications.\n+\n+As a temporary validation step, add a debug print with\n+\n+.. code-block:: cpp\n+\n+ LOG(VIVID, Debug) << \"Vivid Device Identified\";\n+\n+before the final closing return statement in the ``PipelineHandlerVivid::match``\n+method for when when the pipeline handler successfully matches the\n+``MediaDevice`` and ``MediaEntity`` names.\n+\n+Test that the pipeline handler matches and finds a device by rebuilding, and\n+running\n+\n+.. code-block:: shell\n+\n+ ninja -C build\n+ LIBCAMERA_LOG_LEVELS=Pipeline,VIVID:0 ./build/src/cam/cam -l\n+\n+And you should see output like the below:\n+\n+.. code-block:: shell\n+\n+ DEBUG VIVID vivid.cpp:74 Vivid Device Identified\n+\n+Creating camera devices\n+~~~~~~~~~~~~~~~~~~~~~~~\n+\n+If the pipeline handler successfully matches with the system it is running on,\n+it can proceed to initialization, by creating all the required instances of the\n+``V4L2VideoDevice``, ``V4L2Subdevice`` and ``CameraSensor`` hardware abstraction\n+classes. If the Pipeline handler supports an ISP, it can then also Initialise\n+the IPA module before proceeding to the creation of the Camera devices.\n+\n+An image ``Stream`` represents a sequence of images and data of known size and\n+format, stored in application-accessible memory locations. Typical examples of\n+streams are the ISP processed outputs and the raw images captured at the\n+receivers port output.\n+\n+The Pipeline Handler is responsible for defining the set of Streams associated\n+with the Camera.\n+\n+Each Camera has instance-specific data represented using the `CameraData`_\n+class, which can be extended for the specific needs of the pipeline handler.\n+\n+.. _CameraData: http://libcamera.org/api-html/classlibcamera_1_1CameraData.html\n+\n+\n+To support the Camera we will later register, we need to create a CameraData\n+class that we can implement for our specific Pipeline Handler.\n+\n+Define a new ``VividCameraData()`` class derived from ``CameraData`` by adding\n+the following code before the PipelineHandlerVivid class definition where it\n+will be used:\n+\n+.. code-block:: cpp\n+\n+ class VividCameraData : public CameraData\n+ {\n+ public:\n+ VividCameraData(PipelineHandler *pipe, MediaDevice *media)\n+ : CameraData(pipe), media_(media), video_(nullptr)\n+ {\n+ }\n+\n+ ~VividCameraData()\n+ {\n+ delete video_;\n+ }\n+\n+ int init();\n+ void bufferReady(FrameBuffer *buffer);\n+\n+ MediaDevice *media_;\n+ V4L2VideoDevice *video_;\n+ Stream stream_;\n+ };\n+\n+This example pipeline handler handles a single video device and supports a\n+single stream, represented by the ``VividCameraData`` class members. More\n+complex pipeline handlers might register cameras composed of several video\n+devices and sub-devices, or multiple streams per camera that represent the\n+several components of the image capture pipeline. You should represent all these\n+components in the ``CameraData`` derived class when developing a custom\n+PipelineHandler.\n+\n+In our example VividCameraData we implement an ``init()`` function to prepare\n+the object from our PipelineHandler, however the CameraData class does not\n+specify the interface for initialisation and PipelineHandlers can manage this\n+based on their own needs. Derived CameraData classes are used only by their\n+respective pipeline handlers.\n+\n+The CameraData class stores the context required for each camera instance and\n+is usually responsible for opening all Devices used in the capture pipeline.\n+\n+We can now implement the ``init`` method for our example Pipeline Handler to\n+create a new V4L2 video device from the media entity, which we can specify using\n+the `MediaDevice::getEntityByName`_ method from the MediaDevice. As our example\n+is based upon the simplistic Vivid test device, we only need to open a single\n+capture device named 'vivid-000-vid-cap' by the device.\n+\n+.. _MediaDevice::getEntityByName: http://libcamera.org/api-html/classlibcamera_1_1MediaDevice.html#ad5d9279329ef4987ceece2694b33e230\n+\n+.. code-block:: cpp\n+\n+ int VividCameraData::init()\n+ {\n+ video_ = new V4L2VideoDevice(media_->getEntityByName(\"vivid-000-vid-cap\"));\n+ if (video_->open())\n+ return -ENODEV;\n+\n+ return 0;\n+ }\n+\n+The CameraData should be created and initialised before we move on to register a\n+new Camera device so we need to construct and initialise our\n+VividCameraData after we have identified our device within\n+PipelineHandlerVivid::match(). The VividCameraData is wrapped by a\n+std::unique_ptr to help manage the lifetime of our CameraData instance.\n+\n+If the camera data initialization fails, return ``false`` to indicate the\n+failure to the ``match()`` method and prevent retrying of the pipeline handler.\n+\n+.. code-block:: cpp\n+\n+ std::unique_ptr<VividCameraData> data = std::make_unique<VividCameraData>(this, media);\n+\n+ if (data->init())\n+ return false;\n+\n+\n+Once the camera data has been initialized, the Camera device instances and the\n+associated streams have to be registered. Create a set of streams for the\n+camera, which for this device is only one. You create a camera using the static\n+`Camera::create`_ method, passing the pipeline handler, the id of the camera,\n+and the streams available. Then register the camera and its data with the\n+pipeline handler and camera manager using `registerCamera`_.\n+\n+Finally with a successful construction, we return 'true' indicating that the\n+PipelineHandler successfully matched and constructed a device.\n+\n+.. _Camera::create: http://libcamera.org/api-html/classlibcamera_1_1Camera.html#a453740e0d2a2f495048ae307a85a2574\n+.. _registerCamera: http://libcamera.org/api-html/classlibcamera_1_1PipelineHandler.html#adf02a7f1bbd87aca73c0e8d8e0e6c98b\n+\n+.. code-block:: cpp\n+\n+ std::set<Stream *> streams{ &data->stream_ };\n+ std::shared_ptr<Camera> camera = Camera::create(this, data->video_->deviceName(), streams);\n+ registerCamera(std::move(camera), std::move(data));\n+\n+ return true;\n+\n+\n+Our match function should now look like the following:\n+\n+.. code-block:: cpp\n+\n+ bool PipelineHandlerVivid::match(DeviceEnumerator *enumerator)\n+ {\n+ \tDeviceMatch dm(\"vivid\");\n+ \tdm.add(\"vivid-000-vid-cap\");\n+\n+ \tMediaDevice *media = acquireMediaDevice(enumerator, dm);\n+ \tif (!media)\n+ \t\treturn false;\n+\n+ \tstd::unique_ptr<VividCameraData> data = std::make_unique<VividCameraData>(this, media);\n+\n+ \t/* Locate and open the capture video node. */\n+ \tif (data->init())\n+ \t\treturn false;\n+\n+ \t/* Create and register the camera. */\n+ \tstd::set<Stream *> streams{ &data->stream_ };\n+ \tstd::shared_ptr<Camera> camera = Camera::create(this, data->video_->deviceName(), streams);\n+ \tregisterCamera(std::move(camera), std::move(data));\n+\n+ \treturn true;\n+ }\n+\n+We will need to use our custom CameraData class frequently throughout the\n+pipeline handler, so we add a private convenience helper to our Pipeline handler\n+to obtain and cast the custom CameraData instance from a Camera instance.\n+\n+.. code-block:: cpp\n+\n+ private:\n+ VividCameraData *cameraData(const Camera *camera)\n+ {\n+ return static_cast<VividCameraData *>(\n+ PipelineHandler::cameraData(camera));\n+ }\n+\n+At this point, you need to add the following new includes to provide the Camera\n+interface, and device interaction interfaces.\n+\n+.. code-block:: cpp\n+\n+ #include <libcamera/camera.h>\n+ #include \"libcamera/internal/media_device.h\"\n+ #include \"libcamera/internal/v4l2_videodevice.h\"\n+\n+Registering controls and properties\n+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n+\n+The libcamera `controls framework`_ allows an application to configure the\n+streams capture parameters on a per-frame basis and is also used to advertise\n+immutable properties of the ``Camera`` device.\n+\n+The libcamera controls and properties are defined in YAML form which is\n+processed to automatically generate documentation and interfaces. Controls are\n+defined by the src/libcamera/`control_ids.yaml`_ file and camera properties\n+are defined by src/libcamera/`properties_ids.yaml`_.\n+\n+.. _controls framework: http://libcamera.org/api-html/controls_8h.html\n+.. _control_ids.yaml: http://libcamera.org/api-html/control__ids_8h.html\n+.. _properties_ids.yaml: http://libcamera.org/api-html/property__ids_8h.html\n+\n+Pipeline handlers can optionally register the list of controls an application\n+can set as well as a list of immutable camera properties. Being both\n+Camera-specific values, they are represented in the ``CameraData`` base class,\n+which provides two members for this purpose: the `CameraData::controlInfo_`_ and\n+the `CameraData::properties_`_ fields.\n+\n+.. _CameraData::controlInfo_: http://libcamera.org/api-html/classlibcamera_1_1CameraData.html#ab9fecd05c655df6084a2233872144a52\n+.. _CameraData::properties_: http://libcamera.org/api-html/classlibcamera_1_1CameraData.html#a84002c29f45bd35566c172bb65e7ec0b\n+\n+The ``controlInfo_`` field represents a map of ``ControlId`` instances\n+associated with the limits of valid values supported for the control. More\n+information can be found in the `ControlInfoMap`_ class documentation.\n+\n+.. _ControlInfoMap: http://libcamera.org/api-html/classlibcamera_1_1ControlInfoMap.html\n+\n+Pipeline handlers register controls to expose the tunable device and IPA\n+parameters to applications. Our example pipeline handler only exposes trivial\n+controls of the video device, by registering a ``ControlId`` instance with\n+associated values for each supported V4L2 control but demonstrates the mapping\n+of V4L2 Controls to libcamera ControlIDs.\n+\n+Complete the initialization of the ``VividCameraData`` class by adding the\n+following code to the ``VividCameraData::init()`` method to initialise the\n+controls. For more complex control configurations, this could of course be\n+broken out to a separate function, but for now we just initialise the small set\n+inline in our CameraData init:\n+\n+.. code-block:: cpp\n+\n+ /* Initialise the supported controls. */\n+ const ControlInfoMap &controls = video_->controls();\n+ ControlInfoMap::Map ctrls;\n+\n+ for (const auto &ctrl : controls) {\n+ const ControlId *id;\n+ ControlInfo info;\n+\n+ switch (ctrl.first->id()) {\n+ case V4L2_CID_BRIGHTNESS:\n+ id = &controls::Brightness;\n+ info = ControlInfo{ { -1.0f }, { 1.0f }, { 0.0f } };\n+ break;\n+ case V4L2_CID_CONTRAST:\n+ id = &controls::Contrast;\n+ info = ControlInfo{ { 0.0f }, { 2.0f }, { 1.0f } };\n+ break;\n+ case V4L2_CID_SATURATION:\n+ id = &controls::Saturation;\n+ info = ControlInfo{ { 0.0f }, { 2.0f }, { 1.0f } };\n+ break;\n+ default:\n+ continue;\n+ }\n+\n+ ctrls.emplace(id, info);\n+ }\n+\n+ controlInfo_ = std::move(ctrls);\n+\n+The ``properties_`` field is a list of ``ControlId`` instances\n+associated with immutable values, which represent static characteristics that can\n+be used by applications to identify camera devices in the system. Properties can be\n+registered by inspecting the values of V4L2 controls from the video devices and\n+camera sensor (for example to retrieve the position and orientation of a camera)\n+or to express other immutable characteristics. The example pipeline handler does\n+not register any property, but examples are available in the libcamera code\n+base.\n+\n+.. TODO: Add a property example to the pipeline handler. At least the model.\n+\n+At this point you need to add the following includes to the top of the file for\n+handling controls:\n+\n+.. code-block:: cpp\n+\n+ #include <libcamera/controls.h>\n+ #include <libcamera/control_ids.h>\n+\n+Generating a default configuration\n+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n+\n+Once ``Camera`` devices and the associated ``Streams`` have been registered, an\n+application can proceed to acquire and configure the camera to prepare it for a\n+frame capture session.\n+\n+Applications specify the requested configuration by assigning a\n+``StreamConfiguration`` instance to each stream they want to enable which\n+expresses the desired image size and pixel format. The stream configurations are\n+grouped in a ``CameraConfiguration`` which is inspected by the pipeline handler\n+and validated to adjust it to a supported configuration. This may involve\n+adjusting the formats or image sizes or alignments for example to match the\n+capabilities of the device.\n+\n+Applications may choose to repeat validation stages, adjusting paramters until a\n+set of validated StreamConfigurations are returned that is acceptable for the\n+applications needs. When the pipeline handler receives a valid camera\n+configuration it can use the image stream configurations to apply settings to\n+the hardware devices.\n+\n+This configuration and validation process is managed with another Pipeline\n+specific class derived from a common base implementation and interface.\n+\n+To support validation in our example pipeline handler, Create a new class called\n+``VividCameraConfiguration`` derived from the base `CameraConfiguration`_ class\n+which we can implement and use within our ``PipelineHandlerVivid`` class.\n+\n+.. _CameraConfiguration: http://libcamera.org/api-html/classlibcamera_1_1CameraConfiguration.html\n+\n+The derived ``CameraConfiguration`` class must override the base class\n+``validate()`` function, where the stream configuration inspection and\n+adjustment happens.\n+\n+.. code-block:: cpp\n+\n+ class VividCameraConfiguration : public CameraConfiguration\n+ {\n+ public:\n+ VividCameraConfiguration();\n+\n+ Status validate() override;\n+ };\n+\n+ VividCameraConfiguration::VividCameraConfiguration()\n+ : CameraConfiguration()\n+ {\n+ }\n+\n+Applications generate a ``CameraConfiguration`` instance by calling the\n+`Camera::generateConfiguration()`_ function, which calls into the pipeline\n+implementation of the overridden `PipelineHandler::generateConfiguration()`_\n+method.\n+\n+.. _Camera::generateConfiguration(): http://libcamera.org/api-html/classlibcamera_1_1Camera.html#a25c80eb7fc9b1cf32692ce0c7f09991d\n+.. _PipelineHandler::generateConfiguration(): http://libcamera.org/api-html/classlibcamera_1_1PipelineHandler.html#a7932e87735695500ce1f8c7ae449b65b\n+\n+Configurations are generated by receiving a list of ``StreamRoles`` instances,\n+which libcamera uses as predefined ways an application intends to use a camera\n+(You can read the full list in the `StreamRole API`_ documentation). These are\n+optional hints on how an application intends to use a stream, and a pipeline\n+handler should return an ideal configuration for each role that is requested.\n+\n+.. _StreamRole API: http://libcamera.org/api-html/stream_8h.html#file_a295d1f5e7828d95c0b0aabc0a8baac03\n+\n+In the pipeline handler ``generateConfiguration`` implementation, remove the\n+``return nullptr;``, create a new instance of the ``CameraConfiguration``\n+derived class, and assign it to a base class pointer.\n+\n+.. code-block:: cpp\n+\n+ VividCameraData *data = cameraData(camera);\n+ CameraConfiguration *config = new VividCameraConfiguration();\n+\n+A ``CameraConfiguration`` is specific to each pipeline, so you can only create\n+it from the pipeline handler code path. Applications can also generate an empty\n+configuration and add desired stream configurations manually. Pipelines must\n+allow for this by returning an empty configuration if no roles are requested.\n+\n+To support this in our PipelineHandlerVivid, next add the following check in\n+``generateConfiguration`` after the Cameraconfiguration has been constructed:\n+\n+.. code-block:: cpp\n+\n+ if (roles.empty())\n+ return config;\n+\n+A production pipeline handler should generate the ``StreamConfiguration`` for\n+all the appropriate stream roles a camera device supports. For this simpler\n+example (with only one stream), the pipeline handler always returns the same\n+configuration, inferred from the underlying V4L2VideoDevice.\n+\n+How it does this is shown below, but examination of the more full-featured\n+pipelines for IPU3, RKISP1 and RaspberryPi are recommend to explore more\n+complex examples.\n+\n+To generate a ``StreamConfiguration``, you need a list of pixel formats and\n+frame sizes which supported outputs of the stream. You can fetch a map of the\n+``V4LPixelFormat`` and ``SizeRange`` supported by the underlying output device,\n+but the pipeline handler needs to convert this to a ``libcamera::PixelFormat``\n+type to pass to applications. We do this here using ``std::transform`` to\n+convert the formats and populate a new ``PixelFormat`` map as shown below.\n+\n+Continue adding the following code example to our ``generateConfiguration``\n+implementation.\n+\n+.. code-block:: cpp\n+\n+ std::map<V4L2PixelFormat, std::vector<SizeRange>> v4l2Formats =\n+ data->video_->formats();\n+ std::map<PixelFormat, std::vector<SizeRange>> deviceFormats;\n+ std::transform(v4l2Formats.begin(), v4l2Formats.end(),\n+ std::inserter(deviceFormats, deviceFormats.begin()),\n+ [&](const decltype(v4l2Formats)::value_type &format) {\n+ return decltype(deviceFormats)::value_type{\n+ format.first.toPixelFormat(),\n+ format.second\n+ };\n+ });\n+\n+The `StreamFormats`_ class holds information about the pixel formats and frame\n+sizes that a stream can support. The class groups size information by the pixel\n+format, which can produce it.\n+\n+.. _StreamFormats: http://libcamera.org/api-html/classlibcamera_1_1StreamFormats.html\n+\n+The code below uses the ``StreamFormats`` class to represent all of the\n+supported pixel formats, associated with a list of frame sizes. It then\n+generates a supported StreamConfiguration to model the information an\n+application can use to configure a single stream.\n+\n+Continue adding the following code to support this:\n+\n+.. code-block:: cpp\n+\n+ StreamFormats formats(deviceFormats);\n+ StreamConfiguration cfg(formats);\n+\n+As well as a list of supported StreamFormats, the StreamConfiguration is also\n+expected to provide an initialsed default configuration. This may be arbitrary,\n+but depending on use case you may which to select an output that matches the\n+Sensor output, or prefer a pixelformat which might provide higher performance on\n+the hardware. The bufferCount represents the number of buffers required to\n+support functional continuous processing on this stream.\n+\n+.. code-block:: cpp\n+\n+ cfg.pixelFormat = formats::BGR888;\n+ cfg.size = { 1280, 720 };\n+ cfg.bufferCount = 4;\n+\n+Finally add each ``StreamConfiguration`` generated to the\n+``CameraConfiguration``, and ensure that it has been validated before returning\n+it to the application. With only a single supported stream, this code adds only\n+a single StreamConfiguration however a StreamConfiguration should be added for\n+each supported role in a device that can handle more streams.\n+\n+Add the following code to complete the implementation of\n+``generateConfiguration``:\n+\n+.. code-block:: cpp\n+\n+ config->addConfiguration(cfg);\n+\n+ config->validate();\n+\n+ return config;\n+\n+To validate a camera configuration, a pipeline handler must implement the\n+`CameraConfiguration::validate()`_ method in it's derived class to inspect all\n+the stream configuration associated to it, make any adjustments required to make\n+the configuration valid, and return the validation status.\n+\n+If changes are made, it marks the configuration as ``Adjusted``, however if the\n+requested configuration is not supported and cannot be adjusted it shall be\n+refused and marked as ``Invalid``.\n+\n+.. _CameraConfiguration::validate(): http://libcamera.org/api-html/classlibcamera_1_1CameraConfiguration.html#a29f8f263384c6149775b6011c7397093\n+\n+The validation phase makes sure all the platform-specific constraints are\n+respected by the requested configuration. The most trivial examples being making\n+sure the requested image formats are supported and the image alignment\n+restrictions adhered to. The pipeline handler specific implementation of\n+``validate()`` shall inspect all the configuration parameters received and never\n+assume they are correct, as applications are free to change the requested stream\n+parameters after the configuration has been generated.\n+\n+Again, this example pipeline handler is simpler, look at the more complex\n+implementations for a realistic example.\n+\n+Add the following function implementation to your file:\n+\n+.. code-block:: cpp\n+\n+ CameraConfiguration::Status VividCameraConfiguration::validate()\n+ {\n+ Status status = Valid;\n+\n+ if (config_.empty())\n+ return Invalid;\n+\n+ if (config_.size() > 1) {\n+ config_.resize(1);\n+ status = Adjusted;\n+ }\n+\n+ StreamConfiguration &cfg = config_[0];\n+\n+ const std::vector<libcamera::PixelFormat> formats = cfg.formats().pixelformats();\n+ if (std::find(formats.begin(), formats.end(), cfg.pixelFormat) == formats.end()) {\n+ cfg.pixelFormat = cfg.formats().pixelformats()[0];\n+ LOG(VIVID, Debug) << \"Adjusting format to \" << cfg.pixelFormat.toString();\n+ status = Adjusted;\n+ }\n+\n+ cfg.bufferCount = 4;\n+\n+ return status;\n+ }\n+\n+Now that we are handling the ``PixelFormat`` type, we also need to add\n+``#include <libcamera/formats.h>`` to the include section before we rebuild the\n+codebase, and test:\n+\n+.. code-block:: shell\n+\n+ ninja -C build\n+ LIBCAMERA_LOG_LEVELS=Pipeline,VIVID:0 ./build/src/cam/cam -c vivid -I\n+\n+You should see the following output showing the capabilites of our new pipeline\n+handler, and showing that our configurations have been generated:\n+\n+.. code-block:: shell\n+\n+ Using camera vivid\n+ 0: 1280x720-BGR888\n+ * Pixelformat: NV21 (320x180)-(3840x2160)/(+0,+0)\n+ - 320x180\n+ - 640x360\n+ - 640x480\n+ - 1280x720\n+ - 1920x1080\n+ - 3840x2160\n+ * Pixelformat: NV12 (320x180)-(3840x2160)/(+0,+0)\n+ - 320x180\n+ - 640x360\n+ - 640x480\n+ - 1280x720\n+ - 1920x1080\n+ - 3840x2160\n+ * Pixelformat: BGRA8888 (320x180)-(3840x2160)/(+0,+0)\n+ - 320x180\n+ - 640x360\n+ - 640x480\n+ - 1280x720\n+ - 1920x1080\n+ - 3840x2160\n+ * Pixelformat: RGBA8888 (320x180)-(3840x2160)/(+0,+0)\n+ - 320x180\n+ - 640x360\n+ - 640x480\n+ - 1280x720\n+ - 1920x1080\n+ - 3840x2160\n+\n+Configuring a device\n+~~~~~~~~~~~~~~~~~~~~\n+\n+With the configuration generated, and optionally modified and re-validated, a\n+pipeline handler needs a method that allows an application to apply a\n+configuration to the hardware devices.\n+\n+The `PipelineHandler::configure()`_ method receives a valid\n+`CameraConfiguration`_ and applies the settings to hardware devices, using its\n+parameters to prepare a device for a streaming session with the desired\n+properties.\n+\n+.. _PipelineHandler::configure(): http://libcamera.org/api-html/classlibcamera_1_1PipelineHandler.html#a930f2a9cdfb51dfb4b9ca3824e84fc29\n+.. _CameraConfiguration: http://libcamera.org/api-html/classlibcamera_1_1CameraConfiguration.html\n+\n+Replace the contents of the stubbed ``PipelineHandlerVivid::configure`` method\n+with the following to obtain the camera data and stream configuration. This\n+pipeline handler supports only a single stream, so it directly obtains the first\n+``StreamConfiguration`` from the camera configuration. A pipeline handler with\n+multiple streams should inspect each StreamConfiguration and configure the\n+system accordingly.\n+\n+.. code-block:: cpp\n+\n+ VividCameraData *data = cameraData(camera);\n+ StreamConfiguration &cfg = config->at(0);\n+ int ret;\n+\n+The Vivid capture device is a V4L2 video device, so we use a `V4L2DeviceFormat`_\n+with the fourcc and size attributes to apply directly to the capture device\n+node. The fourcc attribute is a `V4L2PixelFormat`_ and differs from the\n+``libcamera::PixelFormat``. Converting the format requires knowledge of the\n+plane configuration for multiplanar formats, so you must explicitly convert it\n+using the helper ``V4L2VideoDevice::toV4L2PixelFormat()`` provided by the\n+V4L2VideoDevice instance of which the format will be applied on.\n+\n+.. _V4L2DeviceFormat: http://libcamera.org/api-html/classlibcamera_1_1V4L2DeviceFormat.html\n+.. _V4L2PixelFormat: http://libcamera.org/api-html/classlibcamera_1_1V4L2PixelFormat.html\n+\n+Add the following code beneath the code from above:\n+\n+.. code-block:: cpp\n+\n+ V4L2DeviceFormat format = {};\n+ format.fourcc = data->video_->toV4L2PixelFormat(cfg.pixelFormat);\n+ format.size = cfg.size;\n+\n+Set the video device format defined above using the\n+`V4L2VideoDevice::setFormat()`_ method. You should check if the kernel\n+driver has adjusted the format, as this shows the pipeline handler has failed to\n+handle the validation stages correctly, and the configure operation shall also\n+fail.\n+\n+.. _V4L2VideoDevice::setFormat(): http://libcamera.org/api-html/classlibcamera_1_1V4L2VideoDevice.html#ad67b47dd9327ce5df43350b80c083cca\n+\n+Continue the implementation with the following code:\n+\n+.. code-block:: cpp\n+\n+ ret = data->video_->setFormat(&format);\n+ if (ret)\n+ return ret;\n+\n+ if (format.size != cfg.size ||\n+ format.fourcc != data->video_->toV4L2PixelFormat(cfg.pixelFormat))\n+ return -EINVAL;\n+\n+Finally, store and set stream-specific data reflecting the state of the stream.\n+Associate the configuration with the stream by using the\n+`StreamConfiguration::setStream`_ method, and set the values of individual\n+stream configuration members as required.\n+\n+.. _StreamConfiguration::setStream: http://libcamera.org/api-html/structlibcamera_1_1StreamConfiguration.html#a74a0eb44dad1b00112c7c0443ae54a12\n+\n+.. NOTE: the cfg.setStream() call here associates the stream to the\n+ StreamConfiguration however that should quite likely be done as part of\n+ the validation process. TBD\n+\n+Complete the configure implementation with the following code:\n+\n+.. code-block:: cpp\n+\n+ cfg.setStream(&data->stream_);\n+ cfg.stride = format.planes[0].bpl;\n+\n+ return 0;\n+\n+.. TODO: stride SHALL be assigned in validate\n+\n+Initializing device controls\n+~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n+\n+Pipeline handlers can optionally initialize the video devices and camera sensor\n+controls at system configuration time, to make sure to make sure they are\n+defaulted to sane values. Handling of device controls is again performed using\n+the libcamera `controls framework`_.\n+\n+.. _Controls Framework: http://libcamera.org/api-html/controls_8h.html\n+\n+This section is particularly specific to Vivid as it sets the initial values of\n+controls to match `Vivid Controls`_ defined by the kernel driver. You won’t need\n+any of the code below for your pipeline handler, but it’s included as an example\n+of how to implement functionality your pipeline handler might need.\n+\n+.. _Vivid Controls: https://www.kernel.org/doc/html/latest/admin-guide/media/vivid.html#controls\n+\n+We need to add some definitions at the top of the file for convenience. These\n+come directly from the kernel sources:\n+\n+.. code-block:: cpp\n+\n+ #define VIVID_CID_VIVID_BASE (0x00f00000 | 0xf000)\n+ #define VIVID_CID_VIVID_CLASS (0x00f00000 | 1)\n+ #define VIVID_CID_TEST_PATTERN (VIVID_CID_VIVID_BASE + 0)\n+ #define VIVID_CID_OSD_TEXT_MODE (VIVID_CID_VIVID_BASE + 1)\n+ #define VIVID_CID_HOR_MOVEMENT (VIVID_CID_VIVID_BASE + 2)\n+\n+We can now use the V4L2 control IDs to prepare a list of controls with the\n+`ControlList`_ class, and set them using the `ControlList::set()`_ method.\n+\n+.. _ControlList: http://libcamera.org/api-html/classlibcamera_1_1ControlList.html\n+.. _ControlList::set(): http://libcamera.org/api-html/classlibcamera_1_1ControlList.html#a74a1a29abff5243e6e37ace8e24eb4ba\n+\n+In our pipeline ``configure`` method, add the following code after the format\n+has been set and checked to initialise the ControlList and apply it to the\n+device:\n+\n+.. code-block:: cpp\n+\n+ ControlList controls(data->video_->controls());\n+ controls.set(VIVID_CID_TEST_PATTERN, 0);\n+ controls.set(VIVID_CID_OSD_TEXT_MODE, 0);\n+\n+ controls.set(V4L2_CID_BRIGHTNESS, 128);\n+ controls.set(V4L2_CID_CONTRAST, 128);\n+ controls.set(V4L2_CID_SATURATION, 128);\n+\n+ controls.set(VIVID_CID_HOR_MOVEMENT, 5);\n+\n+ ret = data->video_->setControls(&controls);\n+ if (ret) {\n+ LOG(VIVID, Error) << \"Failed to set controls: \" << ret;\n+ return ret < 0 ? ret : -EINVAL;\n+ }\n+\n+These controls configure VIVID to use a default test pattern, and enable all\n+on-screen display text, while configuring sensible brightness, contrast and\n+saturation values. Use the ``controls.set`` method to set individual controls.\n+\n+Buffer handling and stream control\n+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n+\n+Once the system has been configured with the requested parameters, it is now\n+possible for applications to start capturing frames from the ``Camera`` device.\n+\n+Libcamera implements a per-frame request capture model, realized by queueing\n+``Request`` instances to a ``Camera`` object. Before applications can start\n+submitting capture requests the capture pipeline needs to be prepared to deliver\n+frames as soon as they are requested. Memory should be initialized and made\n+available to the devices which have to be started and ready to produce\n+images. At the end of a capture session the ``Camera`` device needs to be\n+stopped, to gracefully clean up any allocated memory and stop the hardware\n+devices. Pipeline handlers implement two methods for these purposes, the\n+``start()`` and ``stop()`` methods.\n+\n+The memory initialization phase that happens at ``start()`` time serves to\n+configure video devices to be able to use memory buffers exported as dma-buf\n+file descriptors. From the pipeline handlers perspective the video devices that\n+provide application facing streams always act as memory importers which use,\n+in V4L2 terminology, buffers of V4L2_MEMORY_DMABUF memory type.\n+\n+Libcamera also provides an API to allocate and export memory to applications\n+realized through the `exportFrameBuffers`_ function and the\n+`FrameBufferAllocator`_ class which will be presented later.\n+\n+.. _exportFrameBuffers: http://libcamera.org/api-html/classlibcamera_1_1PipelineHandler.html#a6312a69da7129c2ed41f9d9f790adf7c\n+.. _FrameBufferAllocator: http://libcamera.org/api-html/classlibcamera_1_1FrameBufferAllocator.html\n+\n+Please refer to the V4L2VideoDevice API documentation, specifically the\n+`allocateBuffers`_, `importBuffers`_ and `exportBuffers`_ functions for a\n+detailed description of the video device memory management.\n+\n+.. _allocateBuffers: http://libcamera.org/api-html/classlibcamera_1_1V4L2VideoDevice.html#a3a1a77e5e6c220ea7878e89485864a1c\n+.. _importBuffers: http://libcamera.org/api-html/classlibcamera_1_1V4L2VideoDevice.html#a154f5283d16ebd5e15d63e212745cb64\n+.. _exportBuffers: http://libcamera.org/api-html/classlibcamera_1_1V4L2VideoDevice.html#ae9c0b0a68f350725b63b73a6da5a2ecd\n+\n+Video memory buffers are represented in libcamera by the `FrameBuffer`_ class.\n+A ``FrameBuffer`` instance has to be associated to each ``Stream`` which is part\n+of a capture ``Request``. Pipeline handlers should prepare the capture devices\n+by importing the dma-buf file descriptors it needs to operate on. This operation\n+is performed by using the ``V4L2VideoDevice`` API, which provides an\n+``importBuffers()`` function that prepares the video device accordingly.\n+\n+.. _FrameBuffer: http://libcamera.org/api-html/classlibcamera_1_1FrameBuffer.html\n+\n+Implement the pipeline handler ``start()`` function by replacing the stub\n+version with the following code:\n+\n+.. code-block:: c++\n+\n+ VividCameraData *data = cameraData(camera);\n+ unsigned int count = data->stream_.configuration().bufferCount;\n+\n+ int ret = data->video_->importBuffers(count);\n+ if (ret < 0)\n+ return ret;\n+\n+ return 0;\n+\n+During the startup phase pipeline handlers allocate any internal buffer pool\n+required to transfer data between different components of the image capture\n+pipeline, for example, between the CSI-2 receiver and the ISP input. The example\n+pipeline does not require any internal pool, but examples are available in more\n+complex pipeline handlers in the libcamera code base.\n+\n+Applications might want to use memory allocated in the video devices instead of\n+allocating it from other parts of the system. libcamera provides an abstraction\n+to assist with this task in the `FrameBufferAllocator`_ class. The\n+``FrameBufferAllocator`` reserves memory for a ``Stream`` in the video device\n+and exports it as dma-buf file descriptors. From this point on, the allocated\n+``FrameBuffer`` are associated to ``Stream`` instances in a ``Request`` and then\n+imported by the pipeline hander in exactly the same fashion as if they were\n+allocated elsewhere.\n+\n+.. _FrameBufferAllocator: http://libcamera.org/api-html/classlibcamera_1_1FrameBufferAllocator.html\n+\n+Pipeline handlers support the ``FrameBufferAllocator`` operations by\n+implementing the `exportFrameBuffers`_ function, which will allocate memory in\n+the video device associated with a stream and export it.\n+\n+.. _exportFrameBuffers: http://libcamera.org/api-html/classlibcamera_1_1PipelineHandler.html#a6312a69da7129c2ed41f9d9f790adf7c\n+\n+Implement the ``exportFrameBuffers`` stub method with the following code to\n+handle this:\n+\n+.. code-block:: cpp\n+\n+ unsigned int count = stream->configuration().bufferCount;\n+ VividCameraData *data = cameraData(camera);\n+\n+ return data->video_->exportBuffers(count, buffers);\n+\n+Once memory has been properly setup, the video devices can be started, to\n+prepare for capture operations. Complete the ``start`` method implementation\n+with the following code:\n+\n+.. code-block:: cpp\n+\n+ ret = data->video_->streamOn();\n+ if (ret < 0) {\n+ data->video_->releaseBuffers();\n+ return ret;\n+ }\n+\n+ return 0;\n+\n+The method starts the video device associated with the stream with the\n+`streamOn`_ method. If the call fails, the error value is propagated to the\n+caller and the `releaseBuffers`_ method releases any buffers to leave the device\n+in a consistent state. If your pipeline handler uses any image processing\n+algorithms, or other devices you should also stop them.\n+\n+.. _streamOn: http://libcamera.org/api-html/classlibcamera_1_1V4L2VideoDevice.html#a588a5dc9d6f4c54c61136ac43ff9a8cc\n+.. _releaseBuffers: http://libcamera.org/api-html/classlibcamera_1_1V4L2VideoDevice.html#a191619c152f764e03bc461611f3fcd35\n+\n+Of course we also need to handle the corresponding actions to stop streaming on\n+a device, Add the following to the ``stop`` method, to stop the stream with the\n+`streamOff`_ method and release all buffers.\n+\n+.. _streamOff: http://libcamera.org/api-html/classlibcamera_1_1V4L2VideoDevice.html#a61998710615bdf7aa25a046c8565ed66\n+\n+.. code-block:: cpp\n+\n+ VividCameraData *data = cameraData(camera);\n+ data->video_->streamOff();\n+ data->video_->releaseBuffers();\n+\n+Queuing requests between applications and hardware\n+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n+\n+libcamera implements a streaming model based on capture requests queued by an\n+application to the ``Camera`` device. Each request contains at least one\n+``Stream`` instance with an associated ``FrameBuffer`` object.\n+\n+When an application sends a capture request, the pipeline handler identifies\n+which video devices have to be provided with buffers to generate a frame from\n+the enabled streams.\n+\n+This example pipeline handler identifies the buffer using the `findBuffer`_\n+helper from the only supported stream and queues it to the capture device\n+directly with the `queueBuffer`_ method provided by the V4L2VideoDevice.\n+\n+.. _findBuffer: http://libcamera.org/api-html/classlibcamera_1_1Request.html#ac66050aeb9b92c64218945158559c4d4\n+.. _queueBuffer: http://libcamera.org/api-html/classlibcamera_1_1V4L2VideoDevice.html#a594cd594686a8c1cf9ae8dba0b2a8a75\n+\n+Replace the stubbed contents of ``queueRequestDevice`` with the following:\n+\n+.. code-block:: cpp\n+\n+ VividCameraData *data = cameraData(camera);\n+ FrameBuffer *buffer = request->findBuffer(&data->stream_);\n+ if (!buffer) {\n+ LOG(VIVID, Error)\n+ << \"Attempt to queue request with invalid stream\";\n+\n+ return -ENOENT;\n+ }\n+\n+ int ret = data->video_->queueBuffer(buffer);\n+ if (ret < 0)\n+ return ret;\n+\n+ return 0;\n+\n+Processing controls\n+~~~~~~~~~~~~~~~~~~~\n+\n+Capture requests not only contain streams and memory buffers, but can\n+optionally contain a list of controls the application has set to modify the\n+streaming parameters.\n+\n+Applications can set controls registered by the pipeline handler in the\n+initialization phase, as explained in the `Registering controls and properties`_\n+section.\n+\n+Implement a ``processControls`` method above the ``queueRequestDevice`` method\n+to loop through the control list received with each request, and inspect the\n+control values. Controls may need to be converted between the libcamera control\n+range definitions and their corresponding values on the device before being set.\n+\n+.. code-block:: cpp\n+\n+ int PipelineHandlerVivid::processControls(VividCameraData *data, Request *request)\n+ {\n+ ControlList controls(data->video_->controls());\n+\n+ for (auto it : request->controls()) {\n+ unsigned int id = it.first;\n+ unsigned int offset;\n+ uint32_t cid;\n+\n+ if (id == controls::Brightness) {\n+ cid = V4L2_CID_BRIGHTNESS;\n+ offset = 128;\n+ } else if (id == controls::Contrast) {\n+ cid = V4L2_CID_CONTRAST;\n+ offset = 0;\n+ } else if (id == controls::Saturation) {\n+ cid = V4L2_CID_SATURATION;\n+ offset = 0;\n+ } else {\n+ continue;\n+ }\n+\n+ int32_t value = lroundf(it.second.get<float>() * 128 + offset);\n+ controls.set(cid, utils::clamp(value, 0, 255));\n+ }\n+\n+ for (const auto &ctrl : controls)\n+ LOG(VIVID, Debug)\n+ << \"Setting control \" << utils::hex(ctrl.first)\n+ << \" to \" << ctrl.second.toString();\n+\n+ int ret = data->video_->setControls(&controls);\n+ if (ret) {\n+ LOG(VIVID, Error) << \"Failed to set controls: \" << ret;\n+ return ret < 0 ? ret : -EINVAL;\n+ }\n+\n+ return ret;\n+ }\n+\n+Declare the function prototype for the ``processControls`` method within the\n+private ``PipelineHandlerVivid`` class members, as it is only used internally as\n+a helper when processing Requests.\n+\n+.. code-block:: cpp\n+\n+ private:\n+ int processControls(VividCameraData *data, Request *request);\n+\n+A pipeline handler is responsible for applying controls provided in a Request to\n+the relevant hardware devices. This could be directly on the capture device, or\n+where appropriate by setting controls on V4L2Subdevices directly. Each pipeline\n+handler is responsible for understanding the correct procedure for applying\n+controls to the device they support.\n+\n+This example pipeline handler applies controls during the `queueRequestDevice`_\n+method for each request, and applies them to the capture device through the\n+capture node.\n+\n+.. _queueRequestDevice: http://libcamera.org/api-html/classlibcamera_1_1PipelineHandler.html#a106914cca210640c9da9ee1f0419e83c\n+\n+In the ``queueRequestDevice`` method, replace the following:\n+\n+.. code-block:: cpp\n+\n+ int ret = data->video_->queueBuffer(buffer);\n+ if (ret < 0)\n+ return ret;\n+\n+With the following code:\n+\n+.. code-block:: cpp\n+\n+ int ret = processControls(data, request);\n+ if (ret < 0)\n+ return ret;\n+\n+ ret = data->video_->queueBuffer(buffer);\n+ if (ret < 0)\n+ return ret;\n+\n+We also need to add the following include directive to support the control\n+value translation operations:\n+\n+.. code-block:: cpp\n+\n+ #include <math.h>\n+\n+Frame completion and event handling\n+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n+\n+Libcamera implements a signals and slots mechanism (similar to `Qt Signals and\n+Slots`_) to connect event sources with callbacks to handle them.\n+\n+As a general summary, a ``Slot`` can be connected to a ``Signal``, which when\n+emitted triggers the execution of the connected slots. A detailed description\n+of the libcamera implementation is available in the `libcamera Signal and Slot`_\n+classes documentation.\n+\n+.. _Qt Signals and Slots: https://doc.qt.io/qt-5/signalsandslots.html\n+.. _libcamera Signal and Slot: http://libcamera.org/api-html/classlibcamera_1_1Signal.html#details\n+\n+In order to notify applications about the availability of new frames and data,\n+the ``Camera`` device exposes two ``Signals`` which applications can connect to\n+be notified of frame completion events. The ``bufferComplete`` signal serves to\n+report to applications the completion event of a single ``Stream`` part of a\n+``Request``, while the ``requestComplete`` signal notifies the completion of all\n+the ``Streams`` and data submitted as part of a request. This mechanism allows\n+implementation of partial request completion, which allows an application to\n+inspect completed buffers associated with the single streams without waiting for\n+all of them to be ready.\n+\n+The ``bufferComplete`` and ``requestComplete`` signals are emitted by the\n+``Camera`` device upon notifications received from the pipeline handler, which\n+tracks the buffers and request completion status.\n+\n+The single buffer completion notification is implemented by pipeline handlers by\n+`connecting`_ the ``bufferReady`` signal of the capture devices they have queued\n+buffers to, to a member function slot that handles processing of the completed\n+frames. When a buffer is ready, the pipeline handler must propagate the\n+completion of that buffer to the Camera by using the PipelineHandler base class\n+``completeBuffer`` function. When all of the buffers referenced by a ``Request``\n+have been completed, the pipeline handler must again notify the ``Camera`` using\n+the PipelineHandler base class ``completeRequest`` function. The PipelineHandler\n+class implementation makes sure the request completion notifications are\n+delivered to applications in the same order as they have been submitted.\n+\n+.. _connecting: http://libcamera.org/api-html/classlibcamera_1_1Signal.html#aa04db72d5b3091ffbb4920565aeed382\n+\n+Returning to the ``int VividCameraData::init()`` method, add the following above\n+the closing ``return 0;`` to connects the pipeline handler ``bufferReady``\n+method to the V4L2 device buffer signal.\n+\n+.. code-block:: cpp\n+\n+ video_->bufferReady.connect(this, &VividCameraData::bufferReady);\n+\n+Create the matching ``VividCameraData::bufferReady`` method after your\n+VividCameradata::init() impelementation.\n+\n+The ``bufferReady`` method obtains the request from the buffer using the\n+``request`` method, and notifies the ``Camera`` that the buffer and\n+request are completed. In this simpler pipeline handler, there is only one\n+stream, so it completes the request immediately. You can find a more complex\n+example of event handling with supporting multiple streams in the libcamera\n+code-base.\n+\n+.. TODO: Add link\n+\n+.. code-block:: cpp\n+\n+ void VividCameraData::bufferReady(FrameBuffer *buffer)\n+ {\n+ Request *request = buffer->request();\n+\n+ pipe_->completeBuffer(camera_, request, buffer);\n+ pipe_->completeRequest(camera_, request);\n+ }\n+\n+Testing a pipeline handler\n+~~~~~~~~~~~~~~~~~~~~~~~~~~\n+\n+Once you've built the pipeline handler, we ca rebuild the code base, and test\n+capture through the pipeline through both of the cam and qcam utilities.\n+\n+.. code-block:: shell\n+\n+ ninja -C build\n+ ./build/src/cam/cam -c vivid -C 5\n+\n+To test that the pipeline handler can detect a device, and capture input.\n+\n+Running the command above outputs (a lot of) information about pixel formats,\n+and then starts capturing frame data, and should provide an output such as the\n+following:\n+\n+.. code-block:: none\n+\n+ user@dev:/home/libcamera$ ./build/src/cam/cam -c vivid -C5\n+ [42:34:08.573066847] [186470] INFO IPAManager ipa_manager.cpp:136 libcamera is not installed. Adding '/home/libcamera/build/src/ipa' to the IPA search path\n+ [42:34:08.575908115] [186470] INFO Camera camera_manager.cpp:287 libcamera v0.0.11+876-7b27d262\n+ [42:34:08.610334268] [186471] INFO IPAProxy ipa_proxy.cpp:122 libcamera is not installed. Loading IPA configuration from '/home/libcamera/src/ipa/vimc/data'\n+ Using camera vivid\n+ [42:34:08.618462130] [186470] WARN V4L2 v4l2_pixelformat.cpp:176 Unsupported V4L2 pixel format Y10\n+ ... <remaining Unsupported V4L2 pixel format warnings can be ignored>\n+ [42:34:08.619901297] [186470] INFO Camera camera.cpp:793 configuring streams: (0) 1280x720-BGR888\n+ Capture 5 frames\n+ fps: 0.00 stream0 seq: 000000 bytesused: 2764800\n+ fps: 4.98 stream0 seq: 000001 bytesused: 2764800\n+ fps: 5.00 stream0 seq: 000002 bytesused: 2764800\n+ fps: 5.03 stream0 seq: 000003 bytesused: 2764800\n+ fps: 5.03 stream0 seq: 000004 bytesused: 2764800\n+\n+This demonstrates that the pipeline handler is successfully capturing frames,\n+but it is helpful to see the visual output and validate the images are being\n+processed correctly. The libcamera project also implements a Qt based\n+application which will render the frames in a window for visual inspection:\n+\n+.. code-block:: shell\n+\n+ ./build/src/qcam/qcam -c vivid\n+\n+.. TODO: Running qcam with the vivid pipeline handler appears to have a bug and\n+ no visual frames are seen. However disabling zero-copy on qcam renders\n+ them successfully.\n\\ No newline at end of file\ndiff --git a/Documentation/index.rst b/Documentation/index.rst\nindex cfcfd388699b..fb391d2b6ebf 100644\n--- a/Documentation/index.rst\n+++ b/Documentation/index.rst\n@@ -14,3 +14,4 @@\n Contribute <contributing>\n \n Developer Guide <guides/introduction>\n+ Pipeline Handler Writers Guide <guides/pipeline-handler>\ndiff --git a/Documentation/meson.build b/Documentation/meson.build\nindex dd7ae700af11..9f6c67071da9 100644\n--- a/Documentation/meson.build\n+++ b/Documentation/meson.build\n@@ -53,6 +53,7 @@ if sphinx.found()\n 'docs.rst',\n 'index.rst',\n 'guides/introduction.rst',\n+ 'guides/pipeline-handler.rst',\n ]\n \n release = 'release=v' + libcamera_git_version\n", "prefixes": [ "libcamera-devel", "v4", "2/3" ] }