[media] V4L2: Add per-device-node capabilities

If V4L2_CAP_DEVICE_CAPS is set, then the new device_caps field is filled with
the capabilities of the opened device node.

The capabilities field traditionally contains the capabilities of the physical
device, being a superset of all capabilities available at the several device
nodes. E.g., if you open /dev/video0, then if it contains VBI caps then that means
that there is a corresponding vbi node as well. And the capabilities field of
both the video and vbi nodes should contain identical caps.

However, it would be very useful to also have a capabilities field that contains
just the caps for the currently open device, hence the new CAP bit and field.

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

1 files changed, 33 insertions, 3 deletions

diff --git a/Documentation/DocBook/media/v4l/vidioc-querycap.xml b/Documentation/DocBook/media/v4l/vidioc-querycap.xml
index e3664d6f2de4..4643505cd4ca 100644
--- a/Documentation/DocBook/media/v4l/vidioc-querycap.xml
+++ b/Documentation/DocBook/media/v4l/vidioc-querycap.xml
@@ -124,12 +124,35 @@ printf ("Version: %u.%u.%u\n",
           <row>
             <entry>__u32</entry>
             <entry><structfield>capabilities</structfield></entry>
-            <entry>Device capabilities, see <xref
-                linkend="device-capabilities" />.</entry>
+            <entry>Available capabilities of the physical device as a whole, see <xref
+                linkend="device-capabilities" />. The same physical device can export
+                multiple devices in /dev (e.g. /dev/videoX, /dev/vbiY and /dev/radioZ).
+                The <structfield>capabilities</structfield> field should contain a union
+                of all capabilities available around the several V4L2 devices exported
+                to userspace.
+                For all those devices the <structfield>capabilities</structfield> field
+                returns the same set of capabilities. This allows applications to open
+                just one of the devices (typically the video device) and discover whether
+                video, vbi and/or radio are also supported.
+            </entry>
           </row>
           <row>
             <entry>__u32</entry>
-            <entry><structfield>reserved</structfield>[4]</entry>
+            <entry><structfield>device_caps</structfield></entry>
+            <entry>Device capabilities of the opened device, see <xref
+                linkend="device-capabilities" />. Should contain the available capabilities
+                of that specific device node. So, for example, <structfield>device_caps</structfield>
+                of a radio device will only contain radio related capabilities and
+                no video or vbi capabilities. This field is only set if the <structfield>capabilities</structfield>
+                field contains the <constant>V4L2_CAP_DEVICE_CAPS</constant> capability.
+                Only the <structfield>capabilities</structfield> field can have the
+                <constant>V4L2_CAP_DEVICE_CAPS</constant> capability, <structfield>device_caps</structfield>
+                will never set <constant>V4L2_CAP_DEVICE_CAPS</constant>.
+            </entry>
+          </row>
+          <row>
+            <entry>__u32</entry>
+            <entry><structfield>reserved</structfield>[3]</entry>
             <entry>Reserved for future extensions. Drivers must set
 this array to zero.</entry>
           </row>
@@ -276,6 +299,13 @@ linkend="async">asynchronous</link> I/O methods.</entry>
             <entry>The device supports the <link
 linkend="mmap">streaming</link> I/O method.</entry>
           </row>
+          <row>
+            <entry><constant>V4L2_CAP_DEVICE_CAPS</constant></entry>
+            <entry>0x80000000</entry>
+            <entry>The driver fills the <structfield>device_caps</structfield>
+            field. This capability can only appear in the <structfield>capabilities</structfield>
+            field and never in the <structfield>device_caps</structfield> field.</entry>
+          </row>
         </tbody>
       </tgroup>
     </table>