Document kern.video.record.

With help/input from jmc@ and kn@.

ok jmc@

3 files changed, 45 insertions, 11 deletions

diff --git a/lib/libc/sys/sysctl.2 b/lib/libc/sys/sysctl.2
index 0b9be238c59..d430659cde3 100644
--- a/lib/libc/sys/sysctl.2
+++ b/lib/libc/sys/sysctl.2
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: sysctl.2,v 1.41 2020/08/04 09:32:05 mvs Exp $
+.\"	$OpenBSD: sysctl.2,v 1.42 2020/12/29 12:28:23 mglocker Exp $
 .\"
 .\" Copyright (c) 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -27,7 +27,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: August 4 2020 $
+.Dd $Mdocdate: December 29 2020 $
 .Dt SYSCTL 2
 .Os
 .Sh NAME
@@ -491,6 +491,7 @@ information.
 .It Dv KERN_TTYCOUNT Ta "integer" Ta "no"
 .It Dv KERN_UTC_OFFSET Ta "integer" Ta "yes"
 .It Dv KERN_VERSION Ta "string" Ta "no"
+.It Dv KERN_VIDEO Ta "node" Ta "yes"
 .It Dv KERN_WATCHDOG Ta "node" Ta "not applicable"
 .It Dv KERN_WITNESS Ta "node" Ta "not applicable"
 .It Dv KERN_WXABORT Ta "integer" Ta "yes"
@@ -1104,6 +1105,22 @@ greater than 0,
 this variable may not be changed.
 .It Dv KERN_VERSION Pq Va kern.version
 The system version string.
+.It Dv KERN_VIDEO Pq Va kern.video
+Control device-independent aspects of the
+.Xr video 4
+subsystem.
+Currently, there is one subnode:
+.Bl -column "KERN_VIDEO_RECORD" "integer" "Changeable" -offset indent
+.It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
+.It Dv KERN_VIDEO_RECORD Ta "integer" Ta "yes"
+.El
+.Pp
+Its meaning is as follows:
+.Bl -tag -width "123456"
+.It Dv KERN_VIDEO_RECORD Pq Va kern.video.record
+If set to the default value of 0, recording is blanked for all video devices.
+If the value is non-zero, video recording is enabled.
+.El
 .It Dv KERN_WATCHDOG Pq Va kern.watchdog
 Return information on hardware watchdog timers.
 If the kernel does not support a hardware watchdog timer,
diff --git a/share/man/man4/video.4 b/share/man/man4/video.4
index c5100051b2f..4b3f2f04480 100644
--- a/share/man/man4/video.4
+++ b/share/man/man4/video.4
@@ -1,4 +1,4 @@
-.\" $OpenBSD: video.4,v 1.18 2020/07/31 18:17:17 mglocker Exp $
+.\" $OpenBSD: video.4,v 1.19 2020/12/29 12:28:23 mglocker Exp $
 .\"
 .\" Copyright (c) 2008 Marcus Glocker <mglocker@openbsd.org>
 .\"
@@ -14,7 +14,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: July 31 2020 $
+.Dd $Mdocdate: December 29 2020 $
 .Dt VIDEO 4
 .Os
 .Sh NAME
@@ -40,6 +40,19 @@ Therefore this document mainly describes the V4L2 API parts
 which are supported by the
 .Nm
 driver.
+.Pp
+For security reasons video recording is blanked by default.
+To achieve this, the
+.Nm
+driver blanks image data received from the underlying video hardware driver.
+The superuser can change this behavior using the
+.Va kern.video.record
+.Xr sysctl 2
+variable:
+.Bd -literal -offset indent
+kern.video.record=0	# Recording is blanked (default)
+kern.video.record=1	# Recording is enabled
+.Ed
 .Sh IOCTLS
 The following
 .Xr ioctl 2
diff --git a/share/man/man8/afterboot.8 b/share/man/man8/afterboot.8
index 248e57b53bb..8b4079f857d 100644
--- a/share/man/man8/afterboot.8
+++ b/share/man/man8/afterboot.8
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: afterboot.8,v 1.167 2020/10/23 20:37:45 jmc Exp $
+.\"	$OpenBSD: afterboot.8,v 1.168 2020/12/29 12:28:23 mglocker Exp $
 .\"
 .\" Copyright (c) 1997 Marshall M. Midden
 .\" All rights reserved.
@@ -29,7 +29,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: October 23 2020 $
+.Dd $Mdocdate: December 29 2020 $
 .Dt AFTERBOOT 8
 .\" Originally created by Marshall M. Midden -- 1997-10-20, m4@umn.edu
 .Os
@@ -406,14 +406,18 @@ Consult
 and
 .Xr printcap 5
 if needed.
-.Ss Audio recording
+.Ss Audio and video recording
 The
 .Xr audio 4
-driver by default records only silence.
-Normal audio recording can be enabled by adding the following directive to
+and
+.Xr video 4
+drivers by default record only silence and blanked images.
+Normal recording can be enabled by adding the following directives to
 .Xr sysctl.conf 5 :
-.Pp
-.Dl kern.audio.record=1
+.Bd -literal -offset indent
+kern.audio.record=1
+kern.video.record=1
+.Ed
 .Ss Mail aliases
 Edit
 .Pa /etc/mail/aliases