{"id":26585,"url":"https://patchwork.libcamera.org/api/patches/26585/?format=json","web_url":"https://patchwork.libcamera.org/patch/26585/","project":{"id":1,"url":"https://patchwork.libcamera.org/api/projects/1/?format=json","name":"libcamera","link_name":"libcamera","list_id":"libcamera_core","list_email":"libcamera-devel@lists.libcamera.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260428133952.6582-2-david.plowman@raspberrypi.com>","date":"2026-04-28T13:26:37","name":"[v3,1/3] pipeline: rpi: Simplify delayed controls","commit_ref":null,"pull_url":null,"state":"superseded","archived":false,"hash":"118d6df606795b38292c25a09b55b1d06020b47c","submitter":{"id":42,"url":"https://patchwork.libcamera.org/api/people/42/?format=json","name":"David Plowman","email":"david.plowman@raspberrypi.com"},"delegate":null,"mbox":"https://patchwork.libcamera.org/patch/26585/mbox/","series":[{"id":5891,"url":"https://patchwork.libcamera.org/api/series/5891/?format=json","web_url":"https://patchwork.libcamera.org/project/libcamera/list/?series=5891","date":"2026-04-28T13:26:36","name":"Atomic control lists on Raspberry Pi","version":3,"mbox":"https://patchwork.libcamera.org/series/5891/mbox/"}],"comments":"https://patchwork.libcamera.org/api/patches/26585/comments/","check":"pending","checks":"https://patchwork.libcamera.org/api/patches/26585/checks/","tags":{},"headers":{"Return-Path":"","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 574E9C32F6\n\tfor ;\n\tTue, 28 Apr 2026 13:40:03 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id A64B762FD2;\n\tTue, 28 Apr 2026 15:40:00 +0200 (CEST)","from mail-wm1-x332.google.com (mail-wm1-x332.google.com\n\t[IPv6:2a00:1450:4864:20::332])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 5795262FA9\n\tfor ;\n\tTue, 28 Apr 2026 15:39:58 +0200 (CEST)","by mail-wm1-x332.google.com with SMTP id\n\t5b1f17b1804b1-48334ee0aeaso119535585e9.1\n\tfor ;\n\tTue, 28 Apr 2026 06:39:58 -0700 (PDT)","from davidp-pi5.pitowers.org\n\t([2a00:1098:3142:1f:88ea:c658:5b20:5e46])\n\tby smtp.gmail.com with ESMTPSA id\n\t5b1f17b1804b1-48a77c24ca0sm51374525e9.14.2026.04.28.06.39.57\n\t(version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256);\n\tTue, 28 Apr 2026 06:39:57 -0700 (PDT)"],"Authentication-Results":"lancelot.ideasonboard.com; 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\n\tTue, 28 Apr 2026 06:39:57 -0700 (PDT)","From":"David Plowman ","To":"libcamera-devel@lists.libcamera.org","Cc":"David Plowman ","Subject":"[PATCH v3 1/3] pipeline: rpi: Simplify delayed controls","Date":"Tue, 28 Apr 2026 14:26:37 +0100","Message-ID":"<20260428133952.6582-2-david.plowman@raspberrypi.com>","X-Mailer":"git-send-email 2.47.3","In-Reply-To":"<20260428133952.6582-1-david.plowman@raspberrypi.com>","References":"<20260428133952.6582-1-david.plowman@raspberrypi.com>","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "},"content":"The queueCount_ value is redundant and can be removed.\n\nThe pipeline handler calls the push and applyControls functions in a\nan interleaved manner, so queueCount_ was merely tracking writeCount_,\nand is therefore unnecessary.\n\nSigned-off-by: David Plowman \n---\n .../pipeline/rpi/common/delayed_controls.cpp | 62 +++++++++++--------\n .../pipeline/rpi/common/delayed_controls.h | 1 -\n 2 files changed, 36 insertions(+), 27 deletions(-)","diff":"diff --git a/src/libcamera/pipeline/rpi/common/delayed_controls.cpp b/src/libcamera/pipeline/rpi/common/delayed_controls.cpp\nindex 19c71946..b647174f 100644\n--- a/src/libcamera/pipeline/rpi/common/delayed_controls.cpp\n+++ b/src/libcamera/pipeline/rpi/common/delayed_controls.cpp\n@@ -32,14 +32,15 @@ namespace RPi {\n *\n * Some sensor controls take effect with a delay as the sensor needs time to\n * adjust, for example exposure and analog gain. This is a helper class to deal\n- * with such controls and the intended users are pipeline handlers.\n+ * with such controls.\n *\n- * The idea is to extend the concept of the buffer depth of a pipeline the\n- * application needs to maintain to also cover controls. Just as with buffer\n- * depth if the application keeps the number of requests queued above the\n- * control depth the controls are guaranteed to take effect for the correct\n- * request. The control depth is determined by the control with the greatest\n- * delay.\n+ * The idea is to maintain a queue of controls that have been submitted.\n+ * Whenever a new frame starts, we can \"peak back\" into this queue to send\n+ * controls at the correct number of frames in advance to account for each\n+ * control's delay.\n+ *\n+ * The overall delay for controls becomes the maximum delay of any of the\n+ * controls.\n */\n \n /**\n@@ -119,7 +120,6 @@ DelayedControls::DelayedControls(V4L2Device *device,\n */\n void DelayedControls::reset(unsigned int cookie)\n {\n-\tqueueCount_ = 1;\n \twriteCount_ = 0;\n \tcookies_[0] = cookie;\n \n@@ -146,18 +146,25 @@ void DelayedControls::reset(unsigned int cookie)\n * \\brief Push a set of controls on the queue\n * \\param[in] controls List of controls to add to the device queue\n *\n- * Push a set of controls to the control queue. This increases the control queue\n- * depth by one.\n+ * Push a set of controls to the control queue. The next call to applyControls\n+ * will advance the slot in the queue where the next call to push will write\n+ * controls.\n *\n * \\returns true if \\a controls are accepted, or false otherwise\n */\n bool DelayedControls::push(const ControlList &controls, const unsigned int cookie)\n {\n \t/* Copy state from previous frame. */\n-\tfor (auto &ctrl : values_) {\n-\t\tInfo &info = ctrl.second[queueCount_];\n-\t\tinfo = values_[ctrl.first][queueCount_ - 1];\n-\t\tinfo.updated = false;\n+\tif (writeCount_ > 0) {\n+\t\tfor (auto &ctrl : values_) {\n+\t\t\tInfo &info = ctrl.second[writeCount_];\n+\t\t\tinfo = values_[ctrl.first][writeCount_ - 1];\n+\t\t\tinfo.updated = false;\n+\t\t}\n+\t} else {\n+\t\t/* Although it works, we don't expect this. */\n+\t\tLOG(RPiDelayedControls, Warning)\n+\t\t\t<< \"push called before applyControls\";\n \t}\n \n \t/* Update with new controls. */\n@@ -175,18 +182,17 @@ bool DelayedControls::push(const ControlList &controls, const unsigned int cooki\n \t\tif (controlParams_.find(id) == controlParams_.end())\n \t\t\treturn false;\n \n-\t\tInfo &info = values_[id][queueCount_];\n+\t\tInfo &info = values_[id][writeCount_];\n \n \t\tinfo = Info(control.second);\n \n \t\tLOG(RPiDelayedControls, Debug)\n \t\t\t<< \"Queuing \" << id->name()\n \t\t\t<< \" to \" << info.toString()\n-\t\t\t<< \" at index \" << queueCount_;\n+\t\t\t<< \" at index \" << writeCount_;\n \t}\n \n-\tcookies_[queueCount_] = cookie;\n-\tqueueCount_++;\n+\tcookies_[writeCount_] = cookie;\n \n \treturn true;\n }\n@@ -200,9 +206,9 @@ bool DelayedControls::push(const ControlList &controls, const unsigned int cooki\n * the callers responsibility to not read too old sequence numbers that have been\n * pushed out of the history.\n *\n- * Historic values are evicted by pushing new values onto the queue using\n- * push(). The max history from the current sequence number that yields valid\n- * values are thus 16 minus number of controls pushed.\n+ * Historic values are evicted by new frames arriving and applyControls\n+ * advancing the head of the queue in the ring buffer. The valid history in\n+ * the queue consists of 16 entries from this head of the queue.\n *\n * \\return The controls at \\a sequence number\n */\n@@ -234,6 +240,10 @@ std::pair DelayedControls::get(uint32_t sequence)\n * number. Any user of these helpers is responsible to inform the helper about\n * the start of any frame. This can be connected with ease to the start of a\n * exposure (SOE) V4L2 event.\n+ *\n+ * Controls will be sent to the device, each staggered by the appropriate\n+ * number of frames for that control, so that they are applied at the same\n+ * time.\n */\n void DelayedControls::applyControls(uint32_t sequence)\n {\n@@ -277,12 +287,12 @@ void DelayedControls::applyControls(uint32_t sequence)\n \t\t}\n \t}\n \n-\twriteCount_ = sequence + 1;\n-\n-\twhile (writeCount_ > queueCount_) {\n+\twhile (writeCount_ < sequence + 1) {\n+\t\twriteCount_++;\n \t\tLOG(RPiDelayedControls, Debug)\n-\t\t\t<< \"Queue is empty, auto queue no-op.\";\n-\t\tpush({}, cookies_[queueCount_ - 1]);\n+\t\t\t<< \"Pushing noop with for index \" << writeCount_\n+\t\t\t<< \" with cookie \" << cookies_[writeCount_ - 1];\n+\t\tpush({}, cookies_[writeCount_ - 1]);\n \t}\n \n \tdevice_->setControls(&out);\ndiff --git a/src/libcamera/pipeline/rpi/common/delayed_controls.h b/src/libcamera/pipeline/rpi/common/delayed_controls.h\nindex 487b0057..48ad5a0f 100644\n--- a/src/libcamera/pipeline/rpi/common/delayed_controls.h\n+++ b/src/libcamera/pipeline/rpi/common/delayed_controls.h\n@@ -76,7 +76,6 @@ private:\n \tstd::unordered_map controlParams_;\n \tunsigned int maxDelay_;\n \n-\tuint32_t queueCount_;\n \tuint32_t writeCount_;\n \tstd::unordered_map> values_;\n \tRingBuffer cookies_;\n","prefixes":["v3","1/3"]}