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Controls can be exposed to userspace via a v4l-subdevX device, and userspace has to be able to subscribe to control events so that it is notified when the control changes value. If a control handler is set for the subdev then set the HAS_EVENTS flag automatically into v4l2_subdev_init_finalize() and use v4l2_ctrl_subdev_subscribe_event() and v4l2_event_subdev_unsubscribe() as default if subdev don't have .(un)subscribe control operations. This simplifies subdev drivers by avoiding the need to set the V4L2_SUBDEV_FL_HAS_EVENTS flag and plug the event handlers, and ensures consistency of the API exposed to userspace. Signed-off-by: Tommaso Merciai <tomm.merciai@gmail.com> Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.