[{"id":14043,"web_url":"https://patchwork.libcamera.org/comment/14043/","msgid":"<9a22bbd2-4708-e253-e279-1d4f58b66074@ideasonboard.com>","date":"2020-12-04T10:32:31","subject":"Re: [libcamera-devel] [PATCH v3.1 4/4] simple-cam: Provide\n\tevent-loop backed by libevent","submitter":{"id":4,"url":"https://patchwork.libcamera.org/api/people/4/","name":"Kieran Bingham","email":"kieran.bingham@ideasonboard.com"},"content":"Hi Umang,\n\nOn 04/12/2020 07:52, Umang Jain wrote:\n> libcamera moved its EventDispatcher and Timer API to its internal API,\n> since providing an event loop to applications should not be the job of\n> libcamera. Application utility like cam, were ported to use libevent,\n> hence inspired from that, un-break simple-cam by using the similar\n> implementation to replace the EventDispatcher and Timer functionality\n> by libevent.\n> \n> Signed-off-by: Umang Jain \n\nThanks, this all fixes the build and works nicely.\n\nReviewed-by: Kieran Bingham \n\nMerging this series now.\n\n> ---\n> Updated patch as per Laurent's suggestion on v3 (4/4).\n> ---\n> \n> event_loop.cpp | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++\n> event_loop.h | 45 +++++++++++++++++++++++\n> meson.build | 2 +\n> simple-cam.cpp | 35 +++++++++++-------\n> 4 files changed, 168 insertions(+), 13 deletions(-)\n> create mode 100644 event_loop.cpp\n> create mode 100644 event_loop.h\n> \n> diff --git a/event_loop.cpp b/event_loop.cpp\n> new file mode 100644\n> index 0000000..7b6ea65\n> --- /dev/null\n> +++ b/event_loop.cpp\n> @@ -0,0 +1,99 @@\n> +/* SPDX-License-Identifier: GPL-2.0-or-later */\n> +/*\n> + * Copyright (C) 2020, Google Inc.\n> + *\n> + * event_loop.cpp - Event loop based on cam\n> + */\n> +\n> +#include \"event_loop.h\"\n> +\n> +#include \n> +#include \n> +#include \n> +\n> +EventLoop *EventLoop::instance_ = nullptr;\n> +\n> +EventLoop::EventLoop()\n> +{\n> +\tassert(!instance_);\n> +\n> +\tevthread_use_pthreads();\n> +\tevent_ = event_base_new();\n> +\tinstance_ = this;\n> +}\n> +\n> +EventLoop::~EventLoop()\n> +{\n> +\tinstance_ = nullptr;\n> +\n> +\tevent_base_free(event_);\n> +\tlibevent_global_shutdown();\n> +}\n> +\n> +int EventLoop::exec()\n> +{\n> +\texitCode_ = -1;\n> +\texit_.store(false, std::memory_order_release);\n> +\n> +\twhile (!exit_.load(std::memory_order_acquire)) {\n> +\t\tdispatchCalls();\n> +\t\tevent_base_loop(event_, EVLOOP_NO_EXIT_ON_EMPTY);\n> +\t}\n> +\n> +\treturn exitCode_;\n> +}\n> +\n> +void EventLoop::exit(int code)\n> +{\n> +\texitCode_ = code;\n> +\texit_.store(true, std::memory_order_release);\n> +\tinterrupt();\n> +}\n> +\n> +void EventLoop::interrupt()\n> +{\n> +\tevent_base_loopbreak(event_);\n> +}\n> +\n> +\n> +void EventLoop::timeoutTriggered(int fd, short event, void *arg)\n> +{\n> +\tEventLoop *self = static_cast(arg);\n> +\tself->exit();\n> +}\n> +\n> +void EventLoop::timeout(unsigned int sec)\n> +{\n> +\tstruct event *ev;\n> +\tstruct timeval tv;\n> +\n> +\ttv.tv_sec = sec;\n> +\ttv.tv_usec = 0;\n> +\tev = evtimer_new(event_, &timeoutTriggered, this);\n> +\tevtimer_add(ev, &tv);\n> +}\n> +\n> +void EventLoop::callLater(const std::function &func)\n> +{\n> +\t{\n> +\t\tstd::unique_lock locker(lock_);\n> +\t\tcalls_.push_back(func);\n> +\t}\n> +\n> +\tinterrupt();\n> +}\n> +\n> +void EventLoop::dispatchCalls()\n> +{\n> +\tstd::unique_lock locker(lock_);\n> +\n> +\tfor (auto iter = calls_.begin(); iter != calls_.end(); ) {\n> +\t\tstd::function call = std::move(*iter);\n> +\n> +\t\titer = calls_.erase(iter);\n> +\n> +\t\tlocker.unlock();\n> +\t\tcall();\n> +\t\tlocker.lock();\n> +\t}\n> +}\n> diff --git a/event_loop.h b/event_loop.h\n> new file mode 100644\n> index 0000000..003c3d8\n> --- /dev/null\n> +++ b/event_loop.h\n> @@ -0,0 +1,45 @@\n> +/* SPDX-License-Identifier: GPL-2.0-or-later */\n> +/*\n> + * Copyright (C) 2020, Google Inc.\n> + *\n> + * event_loop.h - Event loop based on cam's\n> + */\n> +#ifndef __SIMPLE_CAM_EVENT_LOOP_H__\n> +#define __SIMPLE_CAM_EVENT_LOOP_H__\n> +\n> +#include \n> +#include \n> +#include \n> +#include \n> +\n> +struct event_base;\n> +\n> +class EventLoop\n> +{\n> +public:\n> +\tEventLoop();\n> +\t~EventLoop();\n> +\n> +\tvoid exit(int code = 0);\n> +\tint exec();\n> +\n> +\tvoid timeout(unsigned int sec);\n> +\tvoid callLater(const std::function &func);\n> +\n> +private:\n> +\tstatic EventLoop *instance_;\n> +\n> +\tstatic void timeoutTriggered(int fd, short event, void *arg);\n> +\n> +\tstruct event_base *event_;\n> +\tstd::atomic exit_;\n> +\tint exitCode_;\n> +\n> +\tstd::list> calls_;\n> +\tstd::mutex lock_;\n> +\n> +\tvoid interrupt();\n> +\tvoid dispatchCalls();\n> +};\n> +\n> +#endif /* __SIMPLE_CAM_EVENT_LOOP_H__ */\n> diff --git a/meson.build b/meson.build\n> index c312f2c..4d580c2 100644\n> --- a/meson.build\n> +++ b/meson.build\n> @@ -8,12 +8,14 @@ project('simple-cam', 'c', 'cpp',\n> # simple-cam.cpp is the fully commented application\n> src_files = files([\n> \t'simple-cam.cpp',\n> +\t'event_loop.cpp',\n> ])\n> \n> # Point your PKG_CONFIG_PATH environment variable to the\n> # libcamera install path camera.pc file ($prefix/lib/pkgconfig/camera.pc)\n> libcamera_deps = [\n> dependency('camera', required : true),\n> + dependency('libevent_pthreads'),\n> ]\n> \n> cpp_arguments = [ '-Wno-unused-parameter', ]\n> diff --git a/simple-cam.cpp b/simple-cam.cpp\n> index bfe30d7..6d1d84f 100644\n> --- a/simple-cam.cpp\n> +++ b/simple-cam.cpp\n> @@ -11,8 +11,13 @@\n> \n> #include \n> \n> +#include \"event_loop.h\"\n> +\n> +#define TIMEOUT_SEC 3\n> +\n> using namespace libcamera;\n> std::shared_ptr camera;\n> +EventLoop loop;\n> \n> /*\n> * --------------------------------------------------------------------\n> @@ -21,13 +26,26 @@ std::shared_ptr camera;\n> * For each Camera::requestCompleted Signal emitted from the Camera the\n> * connected Slot is invoked.\n> *\n> + * The Slot is invoked in the CameraManager's thread, hence one should avoid\n> + * any heavy processing here. The processing of the request shall be re-directed\n> + * to the application's thread instead, so as not to block the CameraManager's\n> + * thread for large amount of time.\n> + *\n> * The Slot receives the Request as a parameter.\n> */\n> +\n> +static void processRequest(Request *request);\n> +\n> static void requestComplete(Request *request)\n> {\n> \tif (request->status() == Request::RequestCancelled)\n> \t\treturn;\n> \n> +\tloop.callLater(std::bind(&processRequest, request));\n> +}\n> +\n> +static void processRequest(Request *request)\n> +{\n> \tconst Request::BufferMap &buffers = request->buffers();\n> \n> \tfor (auto bufferPair : buffers) {\n> @@ -320,20 +338,11 @@ int main()\n> \t *\n> \t * In order to dispatch events received from the video devices, such\n> \t * as buffer completions, an event loop has to be run.\n> -\t *\n> -\t * Libcamera provides its own default event dispatcher realized by\n> -\t * polling a set of file descriptors, but applications can integrate\n> -\t * their own even loop with the Libcamera EventDispatcher.\n> -\t *\n> -\t * Here, as an example, run the poll-based EventDispatcher for 3\n> -\t * seconds.\n> \t */\n> -\tEventDispatcher *dispatcher = cm->eventDispatcher();\n> -\tTimer timer;\n> -\ttimer.start(3000);\n> -\twhile (timer.isRunning())\n> -\t\tdispatcher->processEvents();\n> -\n> +\tloop.timeout(TIMEOUT_SEC);\n> +\tint ret = loop.exec();\n> +\tstd::cout << \"Capture ran for \" << TIMEOUT_SEC << \" seconds and \"\n> +\t\t << \"stopped with exit status: \" << ret << std::endl;\n> \t/*\n> \t * --------------------------------------------------------------------\n> \t * Clean Up\n>","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 42371BE177\n\tfor ;\n\tFri, 4 Dec 2020 10:32:36 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id C3ED5635DB;\n\tFri, 4 Dec 2020 11:32:35 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 8A537635D8\n\tfor ;\n\tFri, 4 Dec 2020 11:32:34 +0100 (CET)","from [192.168.0.217]\n\t(cpc89244-aztw30-2-0-cust3082.18-1.cable.virginm.net [86.31.172.11])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 0F1A599A;\n\tFri, 4 Dec 2020 11:32:34 +0100 (CET)"],"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=\"pHnAXhn6\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1607077954;\n\tbh=LPY0ZpcdVWEVOSzKWepsRaz8m/9kPuxEI48LQG9v5bA=;\n\th=Reply-To:Subject:To:References:From:Date:In-Reply-To:From;\n\tb=pHnAXhn6Rj6wm22Phzcu2HVT202z6VbQnrqN/9/NpzgHfMrSydUTdbWrHKd2+RK5H\n\tUIKgs2mUB08tW0MMOyEaeCEehR+PtOnkCwZ6Esk3C7VeBjwkN4Z1EyIeNbOT9nJKE3\n\tA1Bpy63TrSzTDO5nvTspAqlllFdpKOGsQq09i5s0=","To":"Umang Jain , libcamera-devel@lists.libcamera.org","References":"<20201204065452.2764628-5-email@uajain.com>\n\t<20201204075223.2767557-1-email@uajain.com>","From":"Kieran Bingham ","Autocrypt":"addr=kieran.bingham@ideasonboard.com; keydata=\n\tmQINBFYE/WYBEACs1PwjMD9rgCu1hlIiUA1AXR4rv2v+BCLUq//vrX5S5bjzxKAryRf0uHat\n\tV/zwz6hiDrZuHUACDB7X8OaQcwhLaVlq6byfoBr25+hbZG7G3+5EUl9cQ7dQEdvNj6V6y/SC\n\trRanWfelwQThCHckbobWiQJfK9n7rYNcPMq9B8e9F020LFH7Kj6YmO95ewJGgLm+idg1Kb3C\n\tpotzWkXc1xmPzcQ1fvQMOfMwdS+4SNw4rY9f07Xb2K99rjMwZVDgESKIzhsDB5GY465sCsiQ\n\tcSAZRxqE49RTBq2+EQsbrQpIc8XiffAB8qexh5/QPzCmR4kJgCGeHIXBtgRj+nIkCJPZvZtf\n\tKr2EAbc6tgg6DkAEHJb+1okosV09+0+TXywYvtEop/WUOWQ+zo+Y/OBd+8Ptgt1pDRyOBzL8\n\tRXa8ZqRf0Mwg75D+dKntZeJHzPRJyrlfQokngAAs4PaFt6UfS+ypMAF37T6CeDArQC41V3ko\n\tlPn1yMsVD0p+6i3DPvA/GPIksDC4owjnzVX9kM8Zc5Cx+XoAN0w5Eqo4t6qEVbuettxx55gq\n\t8K8FieAjgjMSxngo/HST8TpFeqI5nVeq0/lqtBRQKumuIqDg+Bkr4L1V/PSB6XgQcOdhtd36\n\tOe9X9dXB8YSNt7VjOcO7BTmFn/Z8r92mSAfHXpb07YJWJosQOQARAQABtDBLaWVyYW4gQmlu\n\tZ2hhbSA8a2llcmFuLmJpbmdoYW1AaWRlYXNvbmJvYXJkLmNvbT6JAlcEEwEKAEECGwMFCwkI\n\tBwIGFQgJCgsCBBYCAwECHgECF4ACGQEWIQSQLdeYP70o/eNy1HqhHkZyEKRh/QUCXWTtygUJ\n\tCyJXZAAKCRChHkZyEKRh/f8dEACTDsbLN2nioNZMwyLuQRUAFcXNolDX48xcUXsWS2QjxaPm\n\tVsJx8Uy8aYkS85mdPBh0C83OovQR/OVbr8AxhGvYqBs3nQvbWuTl/+4od7DfK2VZOoKBAu5S\n\tQK2FYuUcikDqYcFWJ8DQnubxfE8dvzojHEkXw0sA4igINHDDFX3HJGZtLio+WpEFQtCbfTAG\n\tYZslasz1YZRbwEdSsmO3/kqy5eMnczlm8a21A3fKUo3g8oAZEFM+f4DUNzqIltg31OAB/kZS\n\tenKZQ/SWC8PmLg/ZXBrReYakxXtkP6w3FwMlzOlhGxqhIRNiAJfXJBaRhuUWzPOpEDE9q5YJ\n\tBmqQL2WJm1VSNNVxbXJHpaWMH1sA2R00vmvRrPXGwyIO0IPYeUYQa3gsy6k+En/aMQJd27dp\n\taScf9am9PFICPY5T4ppneeJLif2lyLojo0mcHOV+uyrds9XkLpp14GfTkeKPdPMrLLTsHRfH\n\tfA4I4OBpRrEPiGIZB/0im98MkGY/Mu6qxeZmYLCcgD6qz4idOvfgVOrNh+aA8HzIVR+RMW8H\n\tQGBN9f0E3kfwxuhl3omo6V7lDw8XOdmuWZNC9zPq1UfryVHANYbLGz9KJ4Aw6M+OgBC2JpkD\n\thXMdHUkC+d20dwXrwHTlrJi1YNp6rBc+xald3wsUPOZ5z8moTHUX/uPA/qhGsbkCDQRWBP1m\n\tARAAzijkb+Sau4hAncr1JjOY+KyFEdUNxRy+hqTJdJfaYihxyaj0Ee0P0zEi35CbE6lgU0Uz\n\ttih9fiUbSV3wfsWqg1Ut3/5rTKu7kLFp15kF7eqvV4uezXRD3Qu4yjv/rMmEJbbD4cTvGCYI\n\td6MDC417f7vK3hCbCVIZSp3GXxyC1LU+UQr3fFcOyCwmP9vDUR9JV0BSqHHxRDdpUXE26Dk6\n\tmhf0V1YkspE5St814ETXpEus2urZE5yJIUROlWPIL+hm3NEWfAP06vsQUyLvr/GtbOT79vXl\n\tEn1aulcYyu20dRRxhkQ6iILaURcxIAVJJKPi8dsoMnS8pB0QW12AHWuirPF0g6DiuUfPmrA5\n\tPKe56IGlpkjc8cO51lIxHkWTpCMWigRdPDexKX+Sb+W9QWK/0JjIc4t3KBaiG8O4yRX8ml2R\n\t+rxfAVKM6V769P/hWoRGdgUMgYHFpHGSgEt80OKK5HeUPy2cngDUXzwrqiM5Sz6Od0qw5pCk\n\tNlXqI0W/who0iSVM+8+RmyY0OEkxEcci7rRLsGnM15B5PjLJjh1f2ULYkv8s4SnDwMZ/kE04\n\t/UqCMK/KnX8pwXEMCjz0h6qWNpGwJ0/tYIgQJZh6bqkvBrDogAvuhf60Sogw+mH8b+PBlx1L\n\toeTK396wc+4c3BfiC6pNtUS5GpsPMMjYMk7kVvEAEQEAAYkCPAQYAQoAJgIbDBYhBJAt15g/\n\tvSj943LUeqEeRnIQpGH9BQJdizzIBQkLSKZiAAoJEKEeRnIQpGH9eYgQAJpjaWNgqNOnMTmD\n\tMJggbwjIotypzIXfhHNCeTkG7+qCDlSaBPclcPGYrTwCt0YWPU2TgGgJrVhYT20ierN8LUvj\n\t6qOPTd+Uk7NFzL65qkh80ZKNBFddx1AabQpSVQKbdcLb8OFs85kuSvFdgqZwgxA1vl4TFhNz\n\tPZ79NAmXLackAx3sOVFhk4WQaKRshCB7cSl+RIng5S/ThOBlwNlcKG7j7W2MC06BlTbdEkUp\n\tECzuuRBv8wX4OQl+hbWbB/VKIx5HKlLu1eypen/5lNVzSqMMIYkkZcjV2SWQyUGxSwq0O/sx\n\tS0A8/atCHUXOboUsn54qdxrVDaK+6jIAuo8JiRWctP16KjzUM7MO0/+4zllM8EY57rXrj48j\n\tsbEYX0YQnzaj+jO6kJtoZsIaYR7rMMq9aUAjyiaEZpmP1qF/2sYenDx0Fg2BSlLvLvXM0vU8\n\tpQk3kgDu7kb/7PRYrZvBsr21EIQoIjXbZxDz/o7z95frkP71EaICttZ6k9q5oxxA5WC6sTXc\n\tMW8zs8avFNuA9VpXt0YupJd2ijtZy2mpZNG02fFVXhIn4G807G7+9mhuC4XG5rKlBBUXTvPU\n\tAfYnB4JBDLmLzBFavQfvonSfbitgXwCG3vS+9HEwAjU30Bar1PEOmIbiAoMzuKeRm2LVpmq4\n\tWZw01QYHU/GUV/zHJSFk","Organization":"Ideas on Board","Message-ID":"<9a22bbd2-4708-e253-e279-1d4f58b66074@ideasonboard.com>","Date":"Fri, 4 Dec 2020 10:32:31 +0000","User-Agent":"Mozilla/5.0 (X11; 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