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

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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>
This commit is contained in:
Hans Verkuil
2012-01-11 06:45:05 -03:00
committed by Mauro Carvalho Chehab
parent 93596ef7db
commit 583aa3a9b5
7 changed files with 69 additions and 17 deletions
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4
Documentation/DocBook/media/v4l/compat.xml
View File

@@ -2393,6 +2393,10 @@ details.</para>
to the <link linkend="control">User controls class</link>.
</para>
</listitem>
<listitem>
<para>Added the device_caps field to struct v4l2_capabilities and added the new
V4L2_CAP_DEVICE_CAPS capability.</para>
</listitem>
</orderedlist>
</section>

9
Documentation/DocBook/media/v4l/v4l2.xml
View File

@@ -127,6 +127,13 @@ structs, ioctls) must be noted in more detail in the history chapter
(compat.xml), along with the possible impact on existing drivers and
applications. -->
<revision>
<revnumber>3.3</revnumber>
<date>2012-01-11</date>
<authorinitials>hv</authorinitials>
<revremark>Added device_caps field to struct v4l2_capabilities.</revremark>
</revision>
<revision>
<revnumber>3.2</revnumber>
<date>2011-08-26</date>
@@ -417,7 +424,7 @@ and discussions on the V4L mailing list.</revremark>
</partinfo>
<title>Video for Linux Two API Specification</title>
<subtitle>Revision 3.2</subtitle>
<subtitle>Revision 3.3</subtitle>
<chapter id="common">
&sub-common;

36
Documentation/DocBook/media/v4l/vidioc-querycap.xml
View File

@@ -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>