The comments there are good enough for DocBook, however they're
using a wrong format. Fix and add to device-drivers.xml.

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Acked-by: Jonathan Corbet <corbet@lwn.net>

This event indicates that the video device has encountered
a source parameter change during runtime. This can typically be a
resolution change detected by a video decoder OR a format change
detected by an input connector.

This needs to be nofified to the userspace and the application may
be expected to reallocate buffers before proceeding. The application
can subscribe to events on a specific pad or input port which
it is interested in.

Signed-off-by: Arun Kumar K <arun.kk@samsung.com>
Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

Add a v4l2 core helper function that can be used as the subdev
.unsubscribe_event handler. This allows to eliminate some
boilerplate from drivers that are only handling the control events.

Signed-off-by: Sylwester Nawrocki <sylvester.nawrocki@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Update contact information to correspond my e-mail address changes.

Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Write-only ioctls should have a const argument in the ioctl op.
Do this conversion for vidioc_(un)subscribe_event.
Adding const for write-only ioctls was decided during the 2012 Media Workshop.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

If the V4L2_EVENT_SUB_FL_SEND_INITIAL was set, then the application expects
to receive an initial event of the initial value of the control.

However, commit c53c2549333b340e2662dc64ec81323476b69a97 that added the new
v4l2_subscribed_event_ops introduced a regression: while the code still queued
that initial event the __v4l2_event_queue_fh() function was modified to ignore
such requests if sev->elems was 0 (meaning that the event subscription wasn't
finished yet).

And sev->elems was only set to a non-zero value after the add operation
returned.

This patch fixes this by passing the elems value to the add function. Then the
add function can set it before queuing the initial event.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Just like with ctrl events, drivers may want to get called back on
listener add / remove for other event types too. Rather then special
casing all of this in subscribe / unsubscribe event it is better to
use ops for this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

It's getting confusing who is linking to what, so add an overview at
the start of the header.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Thanks to Laurent Pinchart <laurent.pinchart@ideasonboard.com>.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

When the event queue for a subscribed event is full, then the oldest
event is dropped. It would be nice if the contents of that oldest
event could be merged with the next-oldest. That way no information is
lost, only intermediate steps are lost.

This patch adds optional replace() (called when only one kevent was allocated)
and merge() (called when more than one kevent was allocated) callbacks that
will be called to do this job.

These two callbacks are implemented for the V4L2_EVENT_CTRL event.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>