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{
    "id": 17415,
    "url": "https://patchwork.libcamera.org/api/patches/17415/?format=api",
    "web_url": "https://patchwork.libcamera.org/patch/17415/",
    "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": "<20220927023642.12341-5-laurent.pinchart@ideasonboard.com>",
    "date": "2022-09-27T02:36:13",
    "name": "[libcamera-devel,v5,04/33] ipa: libipa: Introduce FrameContextQueue",
    "commit_ref": null,
    "pull_url": null,
    "state": "accepted",
    "archived": false,
    "hash": "5592d410aa93133b690c7b4fec8789bb328c2758",
    "submitter": {
        "id": 2,
        "url": "https://patchwork.libcamera.org/api/people/2/?format=api",
        "name": "Laurent Pinchart",
        "email": "laurent.pinchart@ideasonboard.com"
    },
    "delegate": null,
    "mbox": "https://patchwork.libcamera.org/patch/17415/mbox/",
    "series": [
        {
            "id": 3506,
            "url": "https://patchwork.libcamera.org/api/series/3506/?format=api",
            "web_url": "https://patchwork.libcamera.org/project/libcamera/list/?series=3506",
            "date": "2022-09-27T02:36:09",
            "name": "ipa: Frame context queue, IPU3 & RkISP consolidation, and RkISP1 improvements",
            "version": 5,
            "mbox": "https://patchwork.libcamera.org/series/3506/mbox/"
        }
    ],
    "comments": "https://patchwork.libcamera.org/api/patches/17415/comments/",
    "check": "pending",
    "checks": "https://patchwork.libcamera.org/api/patches/17415/checks/",
    "tags": {},
    "headers": {
        "Return-Path": "<libcamera-devel-bounces@lists.libcamera.org>",
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        "To": "libcamera-devel@lists.libcamera.org",
        "Date": "Tue, 27 Sep 2022 05:36:13 +0300",
        "Message-Id": "<20220927023642.12341-5-laurent.pinchart@ideasonboard.com>",
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        "Subject": "[libcamera-devel] [PATCH v5 04/33] ipa: libipa: Introduce\n\tFrameContextQueue",
        "X-BeenThere": "libcamera-devel@lists.libcamera.org",
        "X-Mailman-Version": "2.1.29",
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        "List-Id": "<libcamera-devel.lists.libcamera.org>",
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        "From": "Laurent Pinchart via libcamera-devel\n\t<libcamera-devel@lists.libcamera.org>",
        "Reply-To": "Laurent Pinchart <laurent.pinchart@ideasonboard.com>",
        "Errors-To": "libcamera-devel-bounces@lists.libcamera.org",
        "Sender": "\"libcamera-devel\" <libcamera-devel-bounces@lists.libcamera.org>"
    },
    "content": "From: Umang Jain <umang.jain@ideasonboard.com>\n\nIntroduce a common implementation in libipa to represent the queue of\nframe contexts.\n\nSigned-off-by: Umang Jain <umang.jain@ideasonboard.com>\nSigned-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>\nSigned-off-by: Jacopo Mondi <jacopo@jmondi.org>\nReviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>\n---\nChanges since v4:\n\n- Documentation improvements\n- White space fixes\n- Rework class documentation\n- Rename FCQueue::init() to FCQueue::alloc()\n- Only clear frame number in clear()\n- Add more \\todo comments\n\nChanges since v3:\n\n- Split the IPU3 changes to a separate patch\n- Use composition instead of inheritance\n- Use vector instead of array for backend storage\n- Make the queue size dynamic\n- Rename initialise() to init()\n---\n src/ipa/libipa/fc_queue.cpp | 118 ++++++++++++++++++++++++++++++++++++\n src/ipa/libipa/fc_queue.h   | 108 +++++++++++++++++++++++++++++++++\n src/ipa/libipa/meson.build  |   2 +\n 3 files changed, 228 insertions(+)\n create mode 100644 src/ipa/libipa/fc_queue.cpp\n create mode 100644 src/ipa/libipa/fc_queue.h",
    "diff": "diff --git a/src/ipa/libipa/fc_queue.cpp b/src/ipa/libipa/fc_queue.cpp\nnew file mode 100644\nindex 000000000000..57a369512554\n--- /dev/null\n+++ b/src/ipa/libipa/fc_queue.cpp\n@@ -0,0 +1,118 @@\n+/* SPDX-License-Identifier: LGPL-2.1-or-later */\n+/*\n+ * Copyright (C) 2022, Google Inc.\n+ *\n+ * fc_queue.cpp - IPA Frame context queue\n+ */\n+\n+#include \"fc_queue.h\"\n+\n+#include <libcamera/base/log.h>\n+\n+namespace libcamera {\n+\n+LOG_DEFINE_CATEGORY(FCQueue)\n+\n+namespace ipa {\n+\n+/**\n+ * \\file fc_queue.h\n+ * \\brief Queue of per-frame contexts\n+ */\n+\n+/**\n+ * \\class FCQueue\n+ * \\brief A support class for managing FrameContext instances in IPA modules\n+ * \\tparam FrameContext The IPA module-specific FrameContext derived class type\n+ *\n+ * Along with the Module and Algorithm classes, the frame context queue is a\n+ * core component of the libipa infrastructure. It stores per-frame contexts\n+ * used by the Algorithm operations. By centralizing the lifetime management of\n+ * the contexts and implementing safeguards against underflows and overflows, it\n+ * simplifies IPA modules and improves their reliability.\n+ *\n+ * The queue references frame contexts by a monotonically increasing sequence\n+ * number. The FCQueue design assumes that this number matches both the sequence\n+ * number of the corresponding frame, as generated by the camera sensor, and the\n+ * sequence number of the request. This allows IPA modules to obtain the frame\n+ * context from any location where a request or a frame is available.\n+ *\n+ * A frame context normally begins its lifetime when the corresponding request\n+ * is queued, way before the frame is captured by the camera sensor. IPA modules\n+ * allocate the context from the queue at that point, calling alloc() using the\n+ * request number. The queue initializes the context, and the IPA module then\n+ * populates it with data from the request. The context can be later retrieved\n+ * with a call to get(), typically when the IPA module is requested to provide\n+ * sensor or ISP parameters or receives statistics for a frame. The frame number\n+ * is used at that point to identify the context.\n+ *\n+ * If an application fails to queue requests to the camera fast enough, frames\n+ * may be produced by the camera sensor and processed by the IPA module without\n+ * a corresponding request having been queued to the IPA module. This creates an\n+ * underrun condition, where the IPA module will try to get a frame context that\n+ * hasn't been allocated. In this case, the get() function will allocate and\n+ * initialize a context for the frame, and log a message. Algorithms will not\n+ * apply the controls associated with the late request, but should otherwise\n+ * behave correctly.\n+ *\n+ * \\todo Mark the frame context with a per-frame control error flag in case of\n+ * underrun, and research how algorithms should handle this.\n+ *\n+ * At its core, the queue uses a circular buffer to avoid dynamic memory\n+ * allocation at runtime. The buffer is pre-allocated with a maximum number of\n+ * entries when the FCQueue instance is constructed. Entries are initialized on\n+ * first use by alloc() or, in underrun conditions, get(). The queue is not\n+ * allowed to overflow, which must be ensured by pipeline handlers never\n+ * queuing more in-flight requests to the IPA module than the queue size. If an\n+ * overflow condition is detected, the queue will log a fatal error.\n+ */\n+\n+/**\n+ * \\fn FCQueue::FCQueue(unsigned int size)\n+ * \\brief Construct a frame contexts queue of a specified size\n+ * \\param[in] size The number of contexts in the queue\n+ */\n+\n+/**\n+ * \\fn FCQueue::clear()\n+ * \\brief Clear the contexts queue\n+ *\n+ * IPA modules must clear the frame context queue at the beginning of a new\n+ * streaming session, in IPAModule::start().\n+ *\n+ * \\todo Fix any issue this may cause with requests queued before the camera is\n+ * started.\n+ */\n+\n+/**\n+ * \\fn FCQueue::alloc(uint32_t frame)\n+ * \\brief Allocate and return a FrameContext for the \\a frame\n+ * \\param[in] frame The frame context sequence number\n+ *\n+ * The first call to obtain a FrameContext from the FCQueue should be handled\n+ * through this function. The FrameContext will be initialised, if not\n+ * initialised already, and returned to the caller.\n+ *\n+ * If the FrameContext was already initialized for this \\a frame, a warning will\n+ * be reported and the previously initialized FrameContext is returned.\n+ *\n+ * Frame contexts are expected to be initialised when a Request is first passed\n+ * to the IPA module in IPAModule::queueRequest().\n+ *\n+ * \\return A reference to the FrameContext for sequence \\a frame\n+ */\n+\n+/**\n+ * \\fn FCQueue::get(uint32_t frame)\n+ * \\brief Obtain the FrameContext for the \\a frame\n+ * \\param[in] frame The frame context sequence number\n+ *\n+ * If the FrameContext is not correctly initialised for the \\a frame, it will be\n+ * initialised.\n+ *\n+ * \\return A reference to the FrameContext for sequence \\a frame\n+ */\n+\n+} /* namespace ipa */\n+\n+} /* namespace libcamera */\ndiff --git a/src/ipa/libipa/fc_queue.h b/src/ipa/libipa/fc_queue.h\nnew file mode 100644\nindex 000000000000..4f5cb5d35253\n--- /dev/null\n+++ b/src/ipa/libipa/fc_queue.h\n@@ -0,0 +1,108 @@\n+/* SPDX-License-Identifier: LGPL-2.1-or-later */\n+/*\n+ * Copyright (C) 2022, Google Inc.\n+ *\n+ * fc_queue.h - IPA Frame context queue\n+ */\n+\n+#pragma once\n+\n+#include <vector>\n+\n+#include <libcamera/base/log.h>\n+\n+namespace libcamera {\n+\n+LOG_DECLARE_CATEGORY(FCQueue)\n+\n+namespace ipa {\n+\n+template<typename FrameContext>\n+class FCQueue\n+{\n+public:\n+\tFCQueue(unsigned int size)\n+\t\t: contexts_(size)\n+\t{\n+\t}\n+\n+\tvoid clear()\n+\t{\n+\t\tfor (FrameContext &ctx : contexts_)\n+\t\t\tctx.frame = 0;\n+\t}\n+\n+\tFrameContext &alloc(const uint32_t frame)\n+\t{\n+\t\tFrameContext &frameContext = contexts_[frame % contexts_.size()];\n+\n+\t\t/*\n+\t\t * Do not re-initialise if a get() call has already fetched this\n+\t\t * frame context to preseve the context.\n+\t\t *\n+\t\t * \\todo If the the sequence number of the context to initialise\n+\t\t * is smaller than the sequence number of the queue slot to use,\n+\t\t * it means that we had a serious request underrun and more\n+\t\t * frames than the queue size has been produced since the last\n+\t\t * time the application has queued a request. Does this deserve\n+\t\t * an error condition ?\n+\t\t */\n+\t\tif (frame != 0 && frame <= frameContext.frame)\n+\t\t\tLOG(FCQueue, Warning)\n+\t\t\t\t<< \"Frame \" << frame << \" already initialised\";\n+\t\telse\n+\t\t\tinit(frameContext, frame);\n+\n+\t\treturn frameContext;\n+\t}\n+\n+\tFrameContext &get(uint32_t frame)\n+\t{\n+\t\tFrameContext &frameContext = contexts_[frame % contexts_.size()];\n+\n+\t\t/*\n+\t\t * If the IPA algorithms try to access a frame context slot which\n+\t\t * has been already overwritten by a newer context, it means the\n+\t\t * frame context queue has overflowed and the desired context\n+\t\t * has been forever lost. The pipeline handler shall avoid\n+\t\t * queueing more requests to the IPA than the frame context\n+\t\t * queue size.\n+\t\t */\n+\t\tif (frame < frameContext.frame)\n+\t\t\tLOG(FCQueue, Fatal) << \"Frame context for \" << frame\n+\t\t\t\t\t    << \" has been overwritten by \"\n+\t\t\t\t\t    << frameContext.frame;\n+\n+\t\tif (frame == frameContext.frame)\n+\t\t\treturn frameContext;\n+\n+\t\t/*\n+\t\t * The frame context has been retrieved before it was\n+\t\t * initialised through the initialise() call. This indicates an\n+\t\t * algorithm attempted to access a Frame context before it was\n+\t\t * queued to the IPA. Controls applied for this request may be\n+\t\t * left unhandled.\n+\t\t *\n+\t\t * \\todo Set an error flag for per-frame control errors.\n+\t\t */\n+\t\tLOG(FCQueue, Warning)\n+\t\t\t<< \"Obtained an uninitialised FrameContext for \" << frame;\n+\n+\t\tinit(frameContext, frame);\n+\n+\t\treturn frameContext;\n+\t}\n+\n+private:\n+\tvoid init(FrameContext &frameContext, const uint32_t frame)\n+\t{\n+\t\tframeContext = {};\n+\t\tframeContext.frame = frame;\n+\t}\n+\n+\tstd::vector<FrameContext> contexts_;\n+};\n+\n+} /* namespace ipa */\n+\n+} /* namespace libcamera */\ndiff --git a/src/ipa/libipa/meson.build b/src/ipa/libipa/meson.build\nindex fb894bc614af..016b8e0ec9be 100644\n--- a/src/ipa/libipa/meson.build\n+++ b/src/ipa/libipa/meson.build\n@@ -3,6 +3,7 @@\n libipa_headers = files([\n     'algorithm.h',\n     'camera_sensor_helper.h',\n+    'fc_queue.h',\n     'histogram.h',\n     'module.h',\n ])\n@@ -10,6 +11,7 @@ libipa_headers = files([\n libipa_sources = files([\n     'algorithm.cpp',\n     'camera_sensor_helper.cpp',\n+    'fc_queue.cpp',\n     'histogram.cpp',\n     'module.cpp',\n ])\n",
    "prefixes": [
        "libcamera-devel",
        "v5",
        "04/33"
    ]
}