[libcamera-devel] [PATCH 00/11] libcamerea: Add support for exclusive access to cameras between processes

[Niklas Söderlund]

Hi,

This series aims to solve mutably exclusive access to a  camera between 
two or more processes by the use of lockf(). In the process of adding 
support for this the MediaDevice implementation is cleaned up a bit and 
stricter call patterns are enforced. At the same time a small load is 
taken of pipeline handler implementations.

As a camera might share resources with other cameras from the same
pipeline handler instance I have chosen to put the granularity of the
lock at the media device level. When a camera is acquired by an
applications all media devices the pipeline handler it belongs to have
claimed are locked and becomes unavailable to other processes. Other
process can still enumerate locked media devices and list all cameras
they provide but they can't use any of the cameras who are backed by a
locked media device.

Patches 1/11 -- 7/11 deals with tidying up and adding more restrictions
to the MediaDevices and how they handled inside pipeline handlers. While
patches 8/11 -- 11/11 adds the new locking scheme which depends on the
new stricter handling of media devices.

Niklas Söderlund (11):
  libcamera: Always check return value of MediaDevice::acquire()
  libcamera: media_device: Open and close media device inside populate()
  libcamera: media_device: Only read device information in populate()
  libcamera: media_device: Handle media device fd in acquire() and
    release()
  test: media_device: Create a common MediaDeviceTest base class
  test: media_device: Add test for acquire() and release()
  libcamera: media_device: Make open() and close() private
  libcamera: media_device: Add functions to lock device for other
    processes
  libcamera: pipeline_handler: Keep track of MediaDevice
  libcamera: pipeline_handler: Add functions to lock a whole pipeline
  libcamera: camera: Lock the pipeline handler in acquire()

 src/libcamera/camera.cpp                      |   7 +
 src/libcamera/device_enumerator.cpp           |   8 +-
 src/libcamera/include/media_device.h          |  10 +-
 src/libcamera/include/pipeline_handler.h      |   7 +
 src/libcamera/media_device.cpp                | 238 +++++++++++-------
 src/libcamera/pipeline/ipu3/ipu3.cpp          |  71 +-----
 src/libcamera/pipeline/rkisp1/rkisp1.cpp      |  57 ++---
 src/libcamera/pipeline/uvcvideo.cpp           |  23 +-
 src/libcamera/pipeline/vimc.cpp               |  21 +-
 src/libcamera/pipeline_handler.cpp            |  71 ++++++
 test/media_device/media_device_basic.cpp      |  41 +++
 test/media_device/media_device_link_test.cpp  |  76 ++----
 test/media_device/media_device_print_test.cpp |  17 --
 test/media_device/media_device_test.cpp       |  41 +++
 test/media_device/media_device_test.h         |  35 +++
 test/media_device/meson.build                 |   3 +-
 test/pipeline/ipu3/ipu3_pipeline_test.cpp     |   5 -
 test/v4l2_device/v4l2_device_test.cpp         |   4 -
 test/v4l2_subdevice/v4l2_subdevice_test.cpp   |  17 +-
 19 files changed, 420 insertions(+), 332 deletions(-)
 create mode 100644 test/media_device/media_device_basic.cpp
 create mode 100644 test/media_device/media_device_test.cpp
 create mode 100644 test/media_device/media_device_test.h

-- 
2.21.0