CVSROOT: /cvs
Module name: src
Changes by: mgloc...@cvs.openbsd.org 2021/02/16 06:50:46
Modified files:
sys/dev : video.c
Log message:
Enable multiple opens of a video(4) device as described in the V4L2
specification:
https://www.kernel.org/doc/html/v5.10/userspace-api/media/v4l/open.html#f1
The discussion has been started by jca@, who has implemented this
behavior recently, but limited to the same process. This diff extends
this behavior to any process. The first process which opens a stream
will become the device owner. Other processes are still allowed to call
certain ioctls, but none which are related to the start/stop of a
stream, or manipulation of the streaming buffers. At the moment only
VIDIOC_G_CTRL and VIDIOC_S_CTRL are supported to be called by non-
device owner processes, which should be extended further in the future.
There is no additional kernel locking implemented at the moment, since
video(4) already runs under the KERNEL_LOCK(), which we expect to be
sufficient for now (as discussed with claudio@).
A lot of improvement input received from anton@.
ok anton@
