[libcamera-devel] [RFC 0/2] android: Introduce CameraWorker

[Jacopo Mondi]

Hi Laurent,

On Thu, Oct 08, 2020 at 06:17:46AM +0300, Laurent Pinchart wrote:
> Hi Jacopo,
>
> On Tue, Oct 06, 2020 at 06:06:35PM +0200, Jacopo Mondi wrote:
> > This two small patches, sent as RFC mostly for comments on the design,
> > implement a worker in the libcamera HAL that is used to handle synchronization
> > fences before queueing a Request to the libcamera::Camera.
> >
> > The camera framework provides, for each buffer part of a capture request
> > an acquisition fence the camera HAL is supposed to wait on before using
> > the buffer. The wait procedure cannot be performed in the Camera HAL thread, as
> > the HAL runs in the global CameraManager thread.
>
> All the operations exposed by the HAL to the camera service are run in
> the camera service thread, not the libcamera CameraManager.
>

Correct, I mixed up the two (in a reply to Niklas too)

> > As fences are handled through a simple poll, it would be possible to install
> > a Notifier for each fence and handle their completion through a Signal in the
> > CameraDevice. Although this would make the class over-complicated.
> >
> > Introducing a worker that synchronously waits on fences using its own thread
> > is a cleaner design a provides a cleaner interface for the CameraDevice.
> >
> > The waitFence() function implementes the same mechanism as the libdrm provided
> > sync_wait() function without introducing an explicit dependency in libcamera.
> >
> >
> > Jacopo Mondi (2):
> >   android: camera_worker: Introduce CameraWorker
> >   android: camera_device: Queue request to Worker
> >
> >  src/android/camera_device.cpp | 21 ++++------
> >  src/android/camera_device.h   |  3 ++
> >  src/android/camera_worker.cpp | 67 +++++++++++++++++++++++++++++++
> >  src/android/camera_worker.h   | 75 +++++++++++++++++++++++++++++++++++
> >  src/android/meson.build       |  1 +
> >  5 files changed, 154 insertions(+), 13 deletions(-)
> >  create mode 100644 src/android/camera_worker.cpp
> >  create mode 100644 src/android/camera_worker.h
>
> --
> Regards,
>
> Laurent Pinchart