From patchwork Sun Apr 14 01:34:55 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Niklas_S=C3=B6derlund?= X-Patchwork-Id: 969 Return-Path: Received: from vsp-unauthed02.binero.net (vsp-unauthed02.binero.net [195.74.38.227]) by lancelot.ideasonboard.com (Postfix) with ESMTPS id 30BB660DB4 for ; Sun, 14 Apr 2019 03:35:14 +0200 (CEST) X-Halon-ID: 895d49aa-5e55-11e9-8e2c-005056917f90 Authorized-sender: niklas@soderlund.pp.se Received: from bismarck.berto.se (unknown [89.233.230.99]) by bin-vsp-out-02.atm.binero.net (Halon) with ESMTPA id 895d49aa-5e55-11e9-8e2c-005056917f90; Sun, 14 Apr 2019 03:35:12 +0200 (CEST) From: =?utf-8?q?Niklas_S=C3=B6derlund?= To: libcamera-devel@lists.libcamera.org Date: Sun, 14 Apr 2019 03:34:55 +0200 Message-Id: <20190414013506.10515-1-niklas.soderlund@ragnatech.se> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Subject: [libcamera-devel] [RFC 00/11] libcamerea: Add support for exclusive access to cameras between processes X-BeenThere: libcamera-devel@lists.libcamera.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 14 Apr 2019 01:35:14 -0000 Hi, This RFC is a proposal on how 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 -- 8/11 deals with tidying up and adding more restrictions to the MediaDevices and how they handled inside pipeline handlers. While patches 9/11 -- 11/11 adds the new locking scheme which depends on the new stricter handling of media devices. As this is a RFC there are some limitations, - Documentation is missing for some of the new functions, but they are pretty straight forward. - The new stricter MediaDevice call schema prevents media_device_link_test to run properly as it now needs access to private functions to operate. As it's outside the scope of this RFC to solve testing of private functions I simply dropped it for now. - Some functions name are not as nice as they could be... I really hate PipelineHandler::tryAcquire(), suggestions are welcome! All comments welcome, including ones telling me I'm a moron! ;-) 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() libcamera: media_device: Make open() and close() private libcamera: pipeline_handler: Keep track of MediaDevice [HACK] tests: disable media_device_link_test libcamera: media_device: Restrict acquire() and release() libcamera: media_device: Add functions to lock device for other processes 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 | 16 +- src/libcamera/include/pipeline_handler.h | 7 + src/libcamera/media_device.cpp | 250 +++++++++--------- src/libcamera/pipeline/ipu3/ipu3.cpp | 47 +--- src/libcamera/pipeline/uvcvideo.cpp | 23 +- src/libcamera/pipeline/vimc.cpp | 21 +- src/libcamera/pipeline_handler.cpp | 40 +++ test/media_device/media_device_link_test.cpp | 9 +- test/media_device/media_device_print_test.cpp | 17 -- test/media_device/meson.build | 1 - test/pipeline/ipu3/ipu3_pipeline_test.cpp | 5 - test/v4l2_device/v4l2_device_test.cpp | 4 - test/v4l2_subdevice/v4l2_subdevice_test.cpp | 16 +- 15 files changed, 216 insertions(+), 255 deletions(-)