From: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Document major, minor and entity_id, and that MEDIA_IOC_DEVICE_INFO
can be called for other media devices as well, besides just the
media controller.
Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
---
.../DocBook/media/v4l/media-ioc-device-info.xml | 35 ++++++++++++++++++----
1 file changed, 30 insertions(+), 5 deletions(-)
diff --git a/Documentation/DocBook/media/v4l/media-ioc-device-info.xml b/Documentation/DocBook/media/v4l/media-ioc-device-info.xml
index 2ce5214..9506cf6 100644
--- a/Documentation/DocBook/media/v4l/media-ioc-device-info.xml
+++ b/Documentation/DocBook/media/v4l/media-ioc-device-info.xml
@@ -49,11 +49,20 @@
<refsect1>
<title>Description</title>
- <para>All media devices must support the <constant>MEDIA_IOC_DEVICE_INFO</constant>
- ioctl. To query device information, applications call the ioctl with a
- pointer to a &media-device-info;. The driver fills the structure and returns
- the information to the application.
- The ioctl never fails.</para>
+ <para>All media devices, both the media controller device itself and any
+ device node used to access a media entity, must support the
+ <constant>MEDIA_IOC_DEVICE_INFO</constant> ioctl. To query device information,
+ applications call the ioctl with a pointer to a &media-device-info;. The driver
+ fills the structure and returns the information to the application.
+ The ioctl never fails, unless it is not a media device, in which case an error
+ is returned, most likely the &ENOTTY;.</para>
+
+ <para>Besides getting the device information from the media controller device
+ itself, applications can use this ioctl as well to check if a device node is part
+ of a media controller. If the ioctl succeeds, then the <structfield>major</structfield>
+ and <structfield>minor</structfield> fields will give you the major and minor
+ numbers of the media controller device and the <structfield>entity_id</structfield>
+ field gives you the entity ID of the media device.</para>
<table pgwide="1" frame="none" id="media-device-info">
<title>struct <structname>media_device_info</structname></title>
@@ -110,6 +119,22 @@
</row>
<row>
<entry>__u32</entry>
+ <entry><structfield>major</structfield></entry>
+ <entry>The major number of the media device node.</entry>
+ </row>
+ <row>
+ <entry>__u32</entry>
+ <entry><structfield>minor</structfield></entry>
+ <entry>The minor number of the media device node.</entry>
+ </row>
+ <row>
+ <entry>__u32</entry>
+ <entry><structfield>entity_id</structfield></entry>
+ <entry>The entity ID if this ioctl was called for a device that is
+ an entity. The media controller will set this to 0.</entry>
+ </row>
+ <row>
+ <entry>__u32</entry>
<entry><structfield>reserved</structfield>[31]</entry>
<entry>Reserved for future extensions. Drivers and applications must
set this array to zero.</entry>
--
2.1.4
--
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