[media] DocBook/v4l: Document the new system-wide version behavior

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

1 files changed, 9 insertions, 1 deletions

diff --git a/Documentation/DocBook/media/v4l/common.xml b/Documentation/DocBook/media/v4l/common.xml
index 9028721..a86f7a0 100644
--- a/Documentation/DocBook/media/v4l/common.xml
+++ b/Documentation/DocBook/media/v4l/common.xml
@@ -236,7 +236,15 @@ important parts of the API.</para>
     <para>The &VIDIOC-QUERYCAP; ioctl is available to check if the kernel
 device is compatible with this specification, and to query the <link
 linkend="devices">functions</link> and <link linkend="io">I/O
-methods</link> supported by the device. Other features can be queried
+methods</link> supported by the device.</para>
+
+    <para>Starting with kernel version 3.1, VIDIOC-QUERYCAP will return the
+V4L2 API version used by the driver, with generally matches the Kernel version.
+There's no need of using &VIDIOC-QUERYCAP; to check if an specific ioctl is
+supported, the V4L2 core now returns ENOIOCTLCMD if a driver doesn't provide
+support for an ioctl.</para>
+
+    <para>Other features can be queried
 by calling the respective ioctl, for example &VIDIOC-ENUMINPUT;
 to learn about the number, types and names of video connectors on the
 device. Although abstraction is a major objective of this API, the