[libcamera-devel] [PATCH v2 1/8] cam: event_loop: Add support for file descriptor events

[Kieran Bingham]

On 03/08/2021 11:43, Laurent Pinchart wrote:
> Hi Kieran,
> 
> On Tue, Aug 03, 2021 at 11:35:34AM +0100, Kieran Bingham wrote:
>> Hi Laurent,
> 
> Yes ? :-)

Agreed. ... ;-)


> 
>> On 30/07/2021 02:02, Laurent Pinchart wrote:
>>> Extend the EventLoop class to support watching file descriptors for
>>> read and write events.
>>>
>>> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

>>> ---
>>>  src/cam/event_loop.cpp | 44 ++++++++++++++++++++++++++++++++++++++++++
>>>  src/cam/event_loop.h   | 20 +++++++++++++++++++
>>>  2 files changed, 64 insertions(+)
>>>
>>> diff --git a/src/cam/event_loop.cpp b/src/cam/event_loop.cpp
>>> index 6a4c47f287d0..e25784c083cf 100644
>>> --- a/src/cam/event_loop.cpp
>>> +++ b/src/cam/event_loop.cpp
>>> @@ -10,6 +10,7 @@
>>>  #include <assert.h>
>>>  #include <event2/event.h>
>>>  #include <event2/thread.h>
>>> +#include <iostream>
>>>  
>>>  EventLoop *EventLoop::instance_ = nullptr;
>>>  
>>> @@ -26,6 +27,7 @@ EventLoop::~EventLoop()
>>>  {
>>>  	instance_ = nullptr;
>>>  
>>> +	events_.clear();
>>>  	event_base_free(base_);
>>>  	libevent_global_shutdown();
>>>  }
>>> @@ -58,6 +60,30 @@ void EventLoop::callLater(const std::function<void()> &func)
>>>  	event_base_once(base_, -1, EV_TIMEOUT, dispatchCallback, this, nullptr);
>>>  }
>>>  
>>> +void EventLoop::addEvent(int fd, EventType type,
>>> +			 const std::function<void()> &callback)
>>> +{
>>> +	std::unique_ptr<Event> event = std::make_unique<Event>(callback);
>>> +	short events = (type & Read ? EV_READ : 0)
>>> +		     | (type & Write ? EV_WRITE : 0)
>>> +		     | EV_PERSIST;
>>> +
>>> +	event->event_ = event_new(base_, fd, events, &EventLoop::Event::dispatch,
>>> +				  event.get());
>>> +	if (!event->event_) {
>>> +		std::cerr << "Failed to create event for fd " << fd << std::endl;
>>> +		return;
>>> +	}
>>> +
>>> +	int ret = event_add(event->event_, nullptr);
>>> +	if (ret < 0) {
>>> +		std::cerr << "Failed to add event for fd " << fd << std::endl;
>>> +		return;
>>> +	}
>>> +
>>> +	events_.push_back(std::move(event));
>>> +}
>>> +
>>>  void EventLoop::dispatchCallback([[maybe_unused]] evutil_socket_t fd,
>>>  				 [[maybe_unused]] short flags, void *param)
>>>  {
>>> @@ -80,3 +106,21 @@ void EventLoop::dispatchCall()
>>>  
>>>  	call();
>>>  }
>>> +
>>> +EventLoop::Event::Event(const std::function<void()> &callback)
>>> +	: callback_(callback), event_(nullptr)
>>> +{
>>> +}
>>> +
>>> +EventLoop::Event::~Event()
>>> +{
>>> +	event_del(event_);
>>> +	event_free(event_);
>>> +}
>>> +
>>> +void EventLoop::Event::dispatch([[maybe_unused]] int fd,
>>> +				[[maybe_unused]] short events, void *arg)
>>> +{
>>> +	Event *event = static_cast<Event *>(arg);
>>> +	event->callback_();
>>> +}
>>> diff --git a/src/cam/event_loop.h b/src/cam/event_loop.h
>>> index ba3ba3a4a675..57bb6fb34aa7 100644
>>> --- a/src/cam/event_loop.h
>>> +++ b/src/cam/event_loop.h
>>> @@ -8,6 +8,7 @@
>>>  #define __CAM_EVENT_LOOP_H__
>>>  
>>>  #include <functional>
>>> +#include <memory>
>>>  #include <list>
>>>  #include <mutex>
>>>  
>>> @@ -18,6 +19,11 @@ struct event_base;
>>>  class EventLoop
>>>  {
>>>  public:
>>> +	enum EventType {
>>> +		Read = 1,
>>> +		Write = 2,
>>> +	};
>>> +
>>>  	EventLoop();
>>>  	~EventLoop();
>>>  
>>> @@ -28,13 +34,27 @@ public:
>>>  
>>>  	void callLater(const std::function<void()> &func);
>>>  
>>> +	void addEvent(int fd, EventType type,
>>> +		      const std::function<void()> &handler);
>>> +
>>>  private:
>>> +	struct Event {
>>> +		Event(const std::function<void()> &callback);
>>> +		~Event();
>>> +
>>> +		static void dispatch(int fd, short events, void *arg);
>>> +
>>> +		std::function<void()> callback_;
>>> +		struct event *event_;
>>> +	};
>>> +
>>>  	static EventLoop *instance_;
>>>  
>>>  	struct event_base *base_;
>>>  	int exitCode_;
>>>  
>>>  	std::list<std::function<void()>> calls_;
>>> +	std::list<std::unique_ptr<Event>> events_;
>>>  	std::mutex lock_;
>>>  
>>>  	static void dispatchCallback(evutil_socket_t fd, short flags,
>>>
>