[libcamera-devel] [PATCH v1 0/5] cam: Move request processing to main thread

[Laurent Pinchart]

Hi Kieran,

On Mon, Nov 16, 2020 at 11:47:49AM +0000, Kieran Bingham wrote:
> On 13/11/2020 06:38, Laurent Pinchart wrote:
> > Hello,
> > 
> > This patch series improves the cam application by moving request
> > processing to the main thread to avoid blocking the camera manager
> > thread (in which the request completion signal is emitted) for extended
> > periods of time. This helps meeting the realtime constraints of pipeline
> > handlers.
> > 
> > Note that move requesting processing to a different thread isn't a
> > magical solution, if the average processing time for a request is larger
> > than the frame interval, a request queue underrun will still occur. It
> > however helps handling random delays in request processing.
> > 
> > Included in the series is a move to libevent to implement the cam event
> > loop. The event loop is currently based on the libcamera event
> > dispatcher for historical reasons. The event dispatcher API exposed by
> > libcamera is incomplete, as thread support is internal to libcamera.
> > Instead of reimplementing the missing parts in the cam event loop, or
> > exposing thread support in the libcamera public API, moving to libevent
> > allows making the event dispatcher implementation fully private (in
> > patch 3/5). It isn't the job of libcamera to provide such generic APIs.
> 
> This series breaks simple-cam.
> 
> Will you plan to update that too?
> If not I'll handle it, just let me know.

If you can handle it, that would be nice. Otherwise I'll do so. Sorry
about the breakage :-S

Regarding the event loop implementation in simple-cam, should we just
copy the one from cam ?

> > Laurent Pinchart (5):
> >   test: Get event dispatcher from current thread
> >   cam: Use libevent to implement event loop
> >   libcamera: Move EventDispatcher to internal API
> >   cam: event_loop: Add deferred calls support
> >   cam: Move request processing to main thread
> > 
> >  include/libcamera/camera_manager.h            |  4 --
> >  .../{ => internal}/event_dispatcher.h         |  0
> >  .../internal/event_dispatcher_poll.h          |  2 +-
> >  .../libcamera/{ => internal}/event_notifier.h |  0
> >  include/libcamera/internal/meson.build        |  3 +
> >  include/libcamera/{ => internal}/timer.h      |  0
> >  include/libcamera/meson.build                 |  3 -
> >  src/cam/capture.cpp                           |  9 +++
> >  src/cam/capture.h                             |  1 +
> >  src/cam/event_loop.cpp                        | 63 ++++++++++++++++---
> >  src/cam/event_loop.h                          | 24 ++++---
> >  src/cam/main.cpp                              | 16 ++---
> >  src/cam/meson.build                           | 13 +++-
> >  src/libcamera/camera_manager.cpp              | 44 +------------
> >  src/libcamera/device_enumerator_udev.cpp      |  3 +-
> >  src/libcamera/event_dispatcher.cpp            |  2 +-
> >  src/libcamera/event_dispatcher_poll.cpp       |  5 +-
> >  src/libcamera/event_notifier.cpp              |  4 +-
> >  src/libcamera/ipc_unixsocket.cpp              |  3 +-
> >  src/libcamera/pipeline/rkisp1/timeline.h      |  3 +-
> >  src/libcamera/process.cpp                     |  3 +-
> >  .../proxy/worker/ipa_proxy_linux_worker.cpp   |  2 +-
> >  src/libcamera/thread.cpp                      |  3 +-
> >  src/libcamera/timer.cpp                       |  4 +-
> >  src/libcamera/v4l2_device.cpp                 |  3 +-
> >  src/libcamera/v4l2_videodevice.cpp            |  2 +-
> >  test/camera/buffer_import.cpp                 |  8 +--
> >  test/camera/capture.cpp                       |  9 ++-
> >  test/event-dispatcher.cpp                     |  5 +-
> >  test/event-thread.cpp                         |  5 +-
> >  test/event.cpp                                |  7 +--
> >  test/hotplug-cameras.cpp                      |  4 +-
> >  test/ipa/ipa_interface_test.cpp               |  6 +-
> >  test/ipc/unixsocket.cpp                       |  5 +-
> >  test/log/log_process.cpp                      |  4 +-
> >  test/object-invoke.cpp                        |  2 +-
> >  test/process/process_test.cpp                 |  5 +-
> >  test/timer-thread.cpp                         |  5 +-
> >  test/timer.cpp                                |  5 +-
> >  test/v4l2_videodevice/buffer_sharing.cpp      |  4 +-
> >  test/v4l2_videodevice/capture_async.cpp       |  4 +-
> >  test/v4l2_videodevice/v4l2_m2mdevice.cpp      |  4 +-
> >  42 files changed, 159 insertions(+), 142 deletions(-)
> >  rename include/libcamera/{ => internal}/event_dispatcher.h (100%)
> >  rename include/libcamera/{ => internal}/event_notifier.h (100%)
> >  rename include/libcamera/{ => internal}/timer.h (100%)

-- 
Regards,

Laurent Pinchart