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

[Niklas Söderlund]

Hi Laurent,

Thanks for your work.

On 2021-07-30 04:02:59 +0300, 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: Niklas Söderlund <niklas.soderlund at ragnatech.se>

> ---
>  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,
> -- 
> Regards,
> 
> Laurent Pinchart
> 

-- 
Regards,
Niklas Söderlund