[media] media: Entities, pads and links enumeration

Create the following two ioctls and implement them at the media device
level to enumerate entities, pads and links.

- MEDIA_IOC_ENUM_ENTITIES: Enumerate entities and their properties
- MEDIA_IOC_ENUM_LINKS: Enumerate all pads and links for a given entity

Entity IDs can be non-contiguous. Userspace applications should
enumerate entities using the MEDIA_ENT_ID_FLAG_NEXT flag. When the flag
is set in the entity ID, the MEDIA_IOC_ENUM_ENTITIES will return the
next entity with an ID bigger than the requested one.

Only forward links that originate at one of the entity's source pads are
returned during the enumeration process.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

8 files changed, 731 insertions, 24 deletions

diff --git a/Documentation/DocBook/media-entities.tmpl b/Documentation/DocBook/media-entities.tmpl
index 034f891..2bd7b27 100644
--- a/Documentation/DocBook/media-entities.tmpl
+++ b/Documentation/DocBook/media-entities.tmpl
@@ -92,6 +92,8 @@
 <!ENTITY VIDIOC-UNSUBSCRIBE-EVENT "<link linkend='vidioc-subscribe-event'><constant>VIDIOC_UNSUBSCRIBE_EVENT</constant></link>">
 
 <!ENTITY MEDIA-IOC-DEVICE-INFO "<link linkend='media-ioc-device-info'><constant>MEDIA_IOC_DEVICE_INFO</constant></link>">
+<!ENTITY MEDIA-IOC-ENUM-ENTITIES "<link linkend='media-ioc-enum-entities'><constant>MEDIA_IOC_ENUM_ENTITIES</constant></link>">
+<!ENTITY MEDIA-IOC-ENUM-LINKS "<link linkend='media-ioc-enum-links'><constant>MEDIA_IOC_ENUM_LINKS</constant></link>">
 
 <!-- Types -->
 <!ENTITY v4l2-std-id "<link linkend='v4l2-std-id'>v4l2_std_id</link>">
@@ -191,6 +193,10 @@
 <!ENTITY v4l2-window "struct&nbsp;<link linkend='v4l2-window'>v4l2_window</link>">
 
 <!ENTITY media-device-info "struct&nbsp;<link linkend='media-device-info'>media_device_info</link>">
+<!ENTITY media-entity-desc "struct&nbsp;<link linkend='media-entity-desc'>media_entity_desc</link>">
+<!ENTITY media-links-enum "struct&nbsp;<link linkend='media-links-enum'>media_links_enum</link>">
+<!ENTITY media-pad-desc "struct&nbsp;<link linkend='media-pad-desc'>media_pad_desc</link>">
+<!ENTITY media-link-desc "struct&nbsp;<link linkend='media-link-desc'>media_link_desc</link>">
 
 <!-- Error Codes -->
 <!ENTITY EACCES "<errorcode>EACCES</errorcode> error code">
@@ -340,6 +346,8 @@
 <!ENTITY sub-media-close SYSTEM "v4l/media-func-close.xml">
 <!ENTITY sub-media-ioctl SYSTEM "v4l/media-func-ioctl.xml">
 <!ENTITY sub-media-ioc-device-info SYSTEM "v4l/media-ioc-device-info.xml">
+<!ENTITY sub-media-ioc-enum-entities SYSTEM "v4l/media-ioc-enum-entities.xml">
+<!ENTITY sub-media-ioc-enum-links SYSTEM "v4l/media-ioc-enum-links.xml">
 
 <!-- Function Reference -->
 <!ENTITY close SYSTEM "v4l/func-close.xml">
diff --git a/Documentation/DocBook/v4l/media-controller.xml b/Documentation/DocBook/v4l/media-controller.xml
index a46b786..2c4fd2b 100644
--- a/Documentation/DocBook/v4l/media-controller.xml
+++ b/Documentation/DocBook/v4l/media-controller.xml
@@ -83,4 +83,6 @@
   &sub-media-ioctl;
   <!-- All ioctls go here. -->
   &sub-media-ioc-device-info;
+  &sub-media-ioc-enum-entities;
+  &sub-media-ioc-enum-links;
 </appendix>
diff --git a/Documentation/DocBook/v4l/media-ioc-device-info.xml b/Documentation/DocBook/v4l/media-ioc-device-info.xml
index 278a312..1f32373 100644
--- a/Documentation/DocBook/v4l/media-ioc-device-info.xml
+++ b/Documentation/DocBook/v4l/media-ioc-device-info.xml
@@ -27,7 +27,8 @@
       <varlistentry>
 	<term><parameter>fd</parameter></term>
 	<listitem>
-	  <para>&fd;</para>
+	  <para>File descriptor returned by
+	  <link linkend='media-func-open'><function>open()</function></link>.</para>
 	</listitem>
       </varlistentry>
       <varlistentry>
diff --git a/Documentation/DocBook/v4l/media-ioc-enum-entities.xml b/Documentation/DocBook/v4l/media-ioc-enum-entities.xml
new file mode 100644
index 0000000..13d0cc4
--- /dev/null
+++ b/Documentation/DocBook/v4l/media-ioc-enum-entities.xml
@@ -0,0 +1,308 @@
+<refentry id="media-ioc-enum-entities">
+  <refmeta>
+    <refentrytitle>ioctl MEDIA_IOC_ENUM_ENTITIES</refentrytitle>
+    &manvol;
+  </refmeta>
+
+  <refnamediv>
+    <refname>MEDIA_IOC_ENUM_ENTITIES</refname>
+    <refpurpose>Enumerate entities and their properties</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <funcsynopsis>
+      <funcprototype>
+	<funcdef>int <function>ioctl</function></funcdef>
+	<paramdef>int <parameter>fd</parameter></paramdef>
+	<paramdef>int <parameter>request</parameter></paramdef>
+	<paramdef>struct media_entity_desc *<parameter>argp</parameter></paramdef>
+      </funcprototype>
+    </funcsynopsis>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Arguments</title>
+
+    <variablelist>
+      <varlistentry>
+	<term><parameter>fd</parameter></term>
+	<listitem>
+	  <para>File descriptor returned by
+	  <link linkend='media-func-open'><function>open()</function></link>.</para>
+	</listitem>
+      </varlistentry>
+      <varlistentry>
+	<term><parameter>request</parameter></term>
+	<listitem>
+	  <para>MEDIA_IOC_ENUM_ENTITIES</para>
+	</listitem>
+      </varlistentry>
+      <varlistentry>
+	<term><parameter>argp</parameter></term>
+	<listitem>
+	  <para></para>
+	</listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
+    <title>Description</title>
+    <para>To query the attributes of an entity, applications set the id field
+    of a &media-entity-desc; structure and call the MEDIA_IOC_ENUM_ENTITIES
+    ioctl with a pointer to this structure. The driver fills the rest of the
+    structure or returns an &EINVAL; when the id is invalid.</para>
+    <para>Entities can be enumerated by or'ing the id with the
+    <constant>MEDIA_ENT_ID_FLAG_NEXT</constant> flag. The driver will return
+    information about the entity with the smallest id strictly larger than the
+    requested one ('next entity'), or the &EINVAL; if there is none.</para>
+    <para>Entity IDs can be non-contiguous. Applications must
+    <emphasis>not</emphasis> try to enumerate entities by calling
+    MEDIA_IOC_ENUM_ENTITIES with increasing id's until they get an error.</para>
+    <para>Two or more entities that share a common non-zero
+    <structfield>group_id</structfield> value are considered as logically
+    grouped. Groups are used to report
+    <itemizedlist>
+      <listitem>ALSA, VBI and video nodes that carry the same media
+      stream</listitem>
+      <listitem>lens and flash controllers associated with a sensor</listitem>
+    </itemizedlist>
+    </para>
+
+    <table pgwide="1" frame="none" id="media-entity-desc">
+      <title>struct <structname>media_entity_desc</structname></title>
+      <tgroup cols="5">
+	<colspec colname="c1" />
+	<colspec colname="c2" />
+	<colspec colname="c3" />
+	<colspec colname="c4" />
+	<colspec colname="c5" />
+	<tbody valign="top">
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>id</structfield></entry>
+	    <entry></entry>
+	    <entry></entry>
+	    <entry>Entity id, set by the application. When the id is or'ed with
+	    <constant>MEDIA_ENT_ID_FLAG_NEXT</constant>, the driver clears the
+	    flag and returns the first entity with a larger id.</entry>
+	  </row>
+	  <row>
+	    <entry>char</entry>
+	    <entry><structfield>name</structfield>[32]</entry>
+	    <entry></entry>
+	    <entry></entry>
+	    <entry>Entity name as an UTF-8 NULL-terminated string.</entry>
+	  </row>
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>type</structfield></entry>
+	    <entry></entry>
+	    <entry></entry>
+	    <entry>Entity type, see <xref linkend="media-entity-type" /> for details.</entry>
+	  </row>
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>revision</structfield></entry>
+	    <entry></entry>
+	    <entry></entry>
+	    <entry>Entity revision in a driver/hardware specific format.</entry>
+	  </row>
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>flags</structfield></entry>
+	    <entry></entry>
+	    <entry></entry>
+	    <entry>Entity flags, see <xref linkend="media-entity-flag" /> for details.</entry>
+	  </row>
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>group_id</structfield></entry>
+	    <entry></entry>
+	    <entry></entry>
+	    <entry>Entity group ID</entry>
+	  </row>
+	  <row>
+	    <entry>__u16</entry>
+	    <entry><structfield>pads</structfield></entry>
+	    <entry></entry>
+	    <entry></entry>
+	    <entry>Number of pads</entry>
+	  </row>
+	  <row>
+	    <entry>__u16</entry>
+	    <entry><structfield>links</structfield></entry>
+	    <entry></entry>
+	    <entry></entry>
+	    <entry>Total number of outbound links. Inbound links are not counted
+	    in this field.</entry>
+	  </row>
+	  <row>
+	    <entry>union</entry>
+	  </row>
+	  <row>
+	    <entry></entry>
+	    <entry>struct</entry>
+	    <entry><structfield>v4l</structfield></entry>
+	    <entry></entry>
+	    <entry>Valid for V4L sub-devices and nodes only.</entry>
+	  </row>
+	  <row>
+	    <entry></entry>
+	    <entry></entry>
+	    <entry>__u32</entry>
+	    <entry><structfield>major</structfield></entry>
+	    <entry>V4L device node major number. For V4L sub-devices with no
+	    device node, set by the driver to 0.</entry>
+	  </row>
+	  <row>
+	    <entry></entry>
+	    <entry></entry>
+	    <entry>__u32</entry>
+	    <entry><structfield>minor</structfield></entry>
+	    <entry>V4L device node minor number. For V4L sub-devices with no
+	    device node, set by the driver to 0.</entry>
+	  </row>
+	  <row>
+	    <entry></entry>
+	    <entry>struct</entry>
+	    <entry><structfield>fb</structfield></entry>
+	    <entry></entry>
+	    <entry>Valid for frame buffer nodes only.</entry>
+	  </row>
+	  <row>
+	    <entry></entry>
+	    <entry></entry>
+	    <entry>__u32</entry>
+	    <entry><structfield>major</structfield></entry>
+	    <entry>Frame buffer device node major number.</entry>
+	  </row>
+	  <row>
+	    <entry></entry>
+	    <entry></entry>
+	    <entry>__u32</entry>
+	    <entry><structfield>minor</structfield></entry>
+	    <entry>Frame buffer device node minor number.</entry>
+	  </row>
+	  <row>
+	    <entry></entry>
+	    <entry>struct</entry>
+	    <entry><structfield>alsa</structfield></entry>
+	    <entry></entry>
+	    <entry>Valid for ALSA devices only.</entry>
+	  </row>
+	  <row>
+	    <entry></entry>
+	    <entry></entry>
+	    <entry>__u32</entry>
+	    <entry><structfield>card</structfield></entry>
+	    <entry>ALSA card number</entry>
+	  </row>
+	  <row>
+	    <entry></entry>
+	    <entry></entry>
+	    <entry>__u32</entry>
+	    <entry><structfield>device</structfield></entry>
+	    <entry>ALSA device number</entry>
+	  </row>
+	  <row>
+	    <entry></entry>
+	    <entry></entry>
+	    <entry>__u32</entry>
+	    <entry><structfield>subdevice</structfield></entry>
+	    <entry>ALSA sub-device number</entry>
+	  </row>
+	  <row>
+	    <entry></entry>
+	    <entry>int</entry>
+	    <entry><structfield>dvb</structfield></entry>
+	    <entry></entry>
+	    <entry>DVB card number</entry>
+	  </row>
+	  <row>
+	    <entry></entry>
+	    <entry>__u8</entry>
+	    <entry><structfield>raw</structfield>[180]</entry>
+	    <entry></entry>
+	    <entry></entry>
+	  </row>
+	</tbody>
+      </tgroup>
+    </table>
+
+    <table frame="none" pgwide="1" id="media-entity-type">
+      <title>Media entity types</title>
+      <tgroup cols="2">
+        <colspec colname="c1"/>
+        <colspec colname="c2"/>
+	<tbody valign="top">
+	  <row>
+	    <entry><constant>MEDIA_ENT_T_DEVNODE</constant></entry>
+	    <entry>Unknown device node</entry>
+	  </row>
+	  <row>
+	    <entry><constant>MEDIA_ENT_T_DEVNODE_V4L</constant></entry>
+	    <entry>V4L video, radio or vbi device node</entry>
+	  </row>
+	  <row>
+	    <entry><constant>MEDIA_ENT_T_DEVNODE_FB</constant></entry>
+	    <entry>Frame buffer device node</entry>
+	  </row>
+	  <row>
+	    <entry><constant>MEDIA_ENT_T_DEVNODE_ALSA</constant></entry>
+	    <entry>ALSA card</entry>
+	  </row>
+	  <row>
+	    <entry><constant>MEDIA_ENT_T_DEVNODE_DVB</constant></entry>
+	    <entry>DVB card</entry>
+	  </row>
+	  <row>
+	    <entry><constant>MEDIA_ENT_T_V4L2_SUBDEV</constant></entry>
+	    <entry>Unknown V4L sub-device</entry>
+	  </row>
+	  <row>
+	    <entry><constant>MEDIA_ENT_T_V4L2_SUBDEV_SENSOR</constant></entry>
+	    <entry>Video sensor</entry>
+	  </row>
+	  <row>
+	    <entry><constant>MEDIA_ENT_T_V4L2_SUBDEV_FLASH</constant></entry>
+	    <entry>Flash controller</entry>
+	  </row>
+	  <row>
+	    <entry><constant>MEDIA_ENT_T_V4L2_SUBDEV_LENS</constant></entry>
+	    <entry>Lens controller</entry>
+	  </row>
+	</tbody>
+      </tgroup>
+    </table>
+
+    <table frame="none" pgwide="1" id="media-entity-flag">
+      <title>Media entity flags</title>
+      <tgroup cols="2">
+        <colspec colname="c1"/>
+        <colspec colname="c2"/>
+	<tbody valign="top">
+	  <row>
+	    <entry><constant>MEDIA_ENT_FL_DEFAULT</constant></entry>
+	    <entry>Default entity for its type. Used to discover the default
+	    audio, VBI and video devices, the default camera sensor, ...</entry>
+	  </row>
+	</tbody>
+      </tgroup>
+    </table>
+  </refsect1>
+
+  <refsect1>
+    &return-value;
+
+    <variablelist>
+      <varlistentry>
+	<term><errorcode>EINVAL</errorcode></term>
+	<listitem>
+	  <para>The &media-entity-desc; <structfield>id</structfield> references
+	  a non-existing entity.</para>
+	</listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+</refentry>
diff --git a/Documentation/DocBook/v4l/media-ioc-enum-links.xml b/Documentation/DocBook/v4l/media-ioc-enum-links.xml
new file mode 100644
index 0000000..6da8841
--- /dev/null
+++ b/Documentation/DocBook/v4l/media-ioc-enum-links.xml
@@ -0,0 +1,202 @@
+<refentry id="media-ioc-enum-links">
+  <refmeta>
+    <refentrytitle>ioctl MEDIA_IOC_ENUM_LINKS</refentrytitle>
+    &manvol;
+  </refmeta>
+
+  <refnamediv>
+    <refname>MEDIA_IOC_ENUM_LINKS</refname>
+    <refpurpose>Enumerate all pads and links for a given entity</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <funcsynopsis>
+      <funcprototype>
+	<funcdef>int <function>ioctl</function></funcdef>
+	<paramdef>int <parameter>fd</parameter></paramdef>
+	<paramdef>int <parameter>request</parameter></paramdef>
+	<paramdef>struct media_links_enum *<parameter>argp</parameter></paramdef>
+      </funcprototype>
+    </funcsynopsis>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Arguments</title>
+
+    <variablelist>
+      <varlistentry>
+	<term><parameter>fd</parameter></term>
+	<listitem>
+	  <para>File descriptor returned by
+	  <link linkend='media-func-open'><function>open()</function></link>.</para>
+	</listitem>
+      </varlistentry>
+      <varlistentry>
+	<term><parameter>request</parameter></term>
+	<listitem>
+	  <para>MEDIA_IOC_ENUM_LINKS</para>
+	</listitem>
+      </varlistentry>
+      <varlistentry>
+	<term><parameter>argp</parameter></term>
+	<listitem>
+	  <para></para>
+	</listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para>To enumerate pads and/or links for a given entity, applications set
+    the entity field of a &media-links-enum; structure and initialize the
+    &media-pad-desc; and &media-link-desc; structure arrays pointed by the
+    <structfield>pads</structfield> and <structfield>links</structfield> fields.
+    They then call the MEDIA_IOC_ENUM_LINKS ioctl with a pointer to this
+    structure.</para>
+    <para>If the <structfield>pads</structfield> field is not NULL, the driver
+    fills the <structfield>pads</structfield> array with information about the
+    entity's pads. The array must have enough room to store all the entity's
+    pads. The number of pads can be retrieved with the &MEDIA-IOC-ENUM-ENTITIES;
+    ioctl.</para>
+    <para>If the <structfield>links</structfield> field is not NULL, the driver
+    fills the <structfield>links</structfield> array with information about the
+    entity's outbound links. The array must have enough room to store all the
+    entity's outbound links. The number of outbound links can be retrieved with
+    the &MEDIA-IOC-ENUM-ENTITIES; ioctl.</para>
+    <para>Only forward links that originate at one of the entity's source pads
+    are returned during the enumeration process.</para>
+
+    <table pgwide="1" frame="none" id="media-links-enum">
+      <title>struct <structname>media_links_enum</structname></title>
+      <tgroup cols="3">
+        &cs-str;
+	<tbody valign="top">
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>entity</structfield></entry>
+	    <entry>Entity id, set by the application.</entry>
+	  </row>
+	  <row>
+	    <entry>struct &media-pad-desc;</entry>
+	    <entry>*<structfield>pads</structfield></entry>
+	    <entry>Pointer to a pads array allocated by the application. Ignored
+	    if NULL.</entry>
+	  </row>
+	  <row>
+	    <entry>struct &media-link-desc;</entry>
+	    <entry>*<structfield>links</structfield></entry>
+	    <entry>Pointer to a links array allocated by the application. Ignored
+	    if NULL.</entry>
+	  </row>
+	</tbody>
+      </tgroup>
+    </table>
+
+    <table pgwide="1" frame="none" id="media-pad-desc">
+      <title>struct <structname>media_pad_desc</structname></title>
+      <tgroup cols="3">
+        &cs-str;
+	<tbody valign="top">
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>entity</structfield></entry>
+	    <entry>ID of the entity this pad belongs to.</entry>
+	  </row>
+	  <row>
+	    <entry>__u16</entry>
+	    <entry><structfield>index</structfield></entry>
+	    <entry>0-based pad index.</entry>
+	  </row>
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>flags</structfield></entry>
+	    <entry>Pad flags, see <xref linkend="media-pad-flag" /> for more details.</entry>
+	  </row>
+	</tbody>
+      </tgroup>
+    </table>
+
+    <table frame="none" pgwide="1" id="media-pad-flag">
+      <title>Media pad flags</title>
+      <tgroup cols="2">
+        <colspec colname="c1"/>
+        <colspec colname="c2"/>
+	<tbody valign="top">
+	  <row>
+	    <entry><constant>MEDIA_PAD_FL_SINK</constant></entry>
+	    <entry>Input pad, relative to the entity. Input pads sink data and
+	    are targets of links.</entry>
+	  </row>
+	  <row>
+	    <entry><constant>MEDIA_PAD_FL_SOURCE</constant></entry>
+	    <entry>Output pad, relative to the entity. Output pads source data
+	    and are origins of links.</entry>
+	  </row>
+	</tbody>
+      </tgroup>
+    </table>
+
+    <table pgwide="1" frame="none" id="media-link-desc">
+      <title>struct <structname>media_links_desc</structname></title>
+      <tgroup cols="3">
+        &cs-str;
+	<tbody valign="top">
+	  <row>
+	    <entry>struct &media-pad-desc;</entry>
+	    <entry><structfield>source</structfield></entry>
+	    <entry>Pad at the origin of this link.</entry>
+	  </row>
+	  <row>
+	    <entry>struct &media-pad-desc;</entry>
+	    <entry><structfield>sink</structfield></entry>
+	    <entry>Pad at the target of this link.</entry>
+	  </row>
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>flags</structfield></entry>
+	    <entry>Link flags, see <xref linkend="media-link-flag" /> for more details.</entry>
+	  </row>
+	</tbody>
+      </tgroup>
+    </table>
+
+    <table frame="none" pgwide="1" id="media-link-flag">
+      <title>Media link flags</title>
+      <tgroup cols="2">
+        <colspec colname="c1"/>
+        <colspec colname="c2"/>
+	<tbody valign="top">
+	  <row>
+	    <entry><constant>MEDIA_LNK_FL_ENABLED</constant></entry>
+	    <entry>The link is enabled and can be used to transfer media data.
+	    When two or more links target a sink pad, only one of them can be
+	    enabled at a time.</entry>
+	  </row>
+	  <row>
+	    <entry><constant>MEDIA_LNK_FL_IMMUTABLE</constant></entry>
+	    <entry>The link enabled state can't be modified at runtime. An
+	    immutable link is always enabled.</entry>
+	  </row>
+	</tbody>
+      </tgroup>
+    </table>
+    <para>One and only one of <constant>MEDIA_PAD_FL_SINK</constant> and
+    <constant>MEDIA_PAD_FL_SOURCE</constant> must be set for every pad.</para>
+  </refsect1>
+
+  <refsect1>
+    &return-value;
+
+    <variablelist>
+      <varlistentry>
+	<term><errorcode>EINVAL</errorcode></term>
+	<listitem>
+	  <para>The &media-links-enum; <structfield>id</structfield> references
+	  a non-existing entity.</para>
+	</listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+</refentry>
diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
index 92e0d4e..648a9d8 100644
--- a/drivers/media/media-device.c
+++ b/drivers/media/media-device.c
@@ -61,6 +61,117 @@ static int media_device_get_info(struct media_device *dev,
 	return copy_to_user(__info, &info, sizeof(*__info));
 }
 
+static struct media_entity *find_entity(struct media_device *mdev, u32 id)
+{
+	struct media_entity *entity;
+	int next = id & MEDIA_ENT_ID_FLAG_NEXT;
+
+	id &= ~MEDIA_ENT_ID_FLAG_NEXT;
+
+	spin_lock(&mdev->lock);
+
+	media_device_for_each_entity(entity, mdev) {
+		if ((entity->id == id && !next) ||
+		    (entity->id > id && next)) {
+			spin_unlock(&mdev->lock);
+			return entity;
+		}
+	}
+
+	spin_unlock(&mdev->lock);
+
+	return NULL;
+}
+
+static long media_device_enum_entities(struct media_device *mdev,
+				       struct media_entity_desc __user *uent)
+{
+	struct media_entity *ent;
+	struct media_entity_desc u_ent;
+
+	if (copy_from_user(&u_ent.id, &uent->id, sizeof(u_ent.id)))
+		return -EFAULT;
+
+	ent = find_entity(mdev, u_ent.id);
+
+	if (ent == NULL)
+		return -EINVAL;
+
+	u_ent.id = ent->id;
+	u_ent.name[0] = '\0';
+	if (ent->name)
+		strlcpy(u_ent.name, ent->name, sizeof(u_ent.name));
+	u_ent.type = ent->type;
+	u_ent.revision = ent->revision;
+	u_ent.flags = ent->flags;
+	u_ent.group_id = ent->group_id;
+	u_ent.pads = ent->num_pads;
+	u_ent.links = ent->num_links - ent->num_backlinks;
+	u_ent.v4l.major = ent->v4l.major;
+	u_ent.v4l.minor = ent->v4l.minor;
+	if (copy_to_user(uent, &u_ent, sizeof(u_ent)))
+		return -EFAULT;
+	return 0;
+}
+
+static void media_device_kpad_to_upad(const struct media_pad *kpad,
+				      struct media_pad_desc *upad)
+{
+	upad->entity = kpad->entity->id;
+	upad->index = kpad->index;
+	upad->flags = kpad->flags;
+}
+
+static long media_device_enum_links(struct media_device *mdev,
+				    struct media_links_enum __user *ulinks)
+{
+	struct media_entity *entity;
+	struct media_links_enum links;
+
+	if (copy_from_user(&links, ulinks, sizeof(links)))
+		return -EFAULT;
+
+	entity = find_entity(mdev, links.entity);
+	if (entity == NULL)
+		return -EINVAL;
+
+	if (links.pads) {
+		unsigned int p;
+
+		for (p = 0; p < entity->num_pads; p++) {
+			struct media_pad_desc pad;
+			media_device_kpad_to_upad(&entity->pads[p], &pad);
+			if (copy_to_user(&links.pads[p], &pad, sizeof(pad)))
+				return -EFAULT;
+		}
+	}
+
+	if (links.links) {
+		struct media_link_desc __user *ulink;
+		unsigned int l;
+
+		for (l = 0, ulink = links.links; l < entity->num_links; l++) {
+			struct media_link_desc link;
+
+			/* Ignore backlinks. */
+			if (entity->links[l].source->entity != entity)
+				continue;
+
+			media_device_kpad_to_upad(entity->links[l].source,
+						  &link.source);
+			media_device_kpad_to_upad(entity->links[l].sink,
+						  &link.sink);
+			link.flags = entity->links[l].flags;
+			if (copy_to_user(ulink, &link, sizeof(*ulink)))
+				return -EFAULT;
+			ulink++;
+		}
+	}
+	if (copy_to_user(ulinks, &links, sizeof(*ulinks)))
+		return -EFAULT;
+	return 0;
+}
+
 static long media_device_ioctl(struct file *filp, unsigned int cmd,
 			       unsigned long arg)
 {
@@ -74,6 +185,18 @@ static long media_device_ioctl(struct file *filp, unsigned int cmd,
 				(struct media_device_info __user *)arg);
 		break;
 
+	case MEDIA_IOC_ENUM_ENTITIES:
+		ret = media_device_enum_entities(dev,
+				(struct media_entity_desc __user *)arg);
+		break;
+
+	case MEDIA_IOC_ENUM_LINKS:
+		mutex_lock(&dev->graph_mutex);
+		ret = media_device_enum_links(dev,
+				(struct media_links_enum __user *)arg);
+		mutex_unlock(&dev->graph_mutex);
+		break;
+
 	default:
 		ret = -ENOIOCTLCMD;
 	}
diff --git a/include/linux/media.h b/include/linux/media.h
index 64090db..17c93a4 100644
--- a/include/linux/media.h
+++ b/include/linux/media.h
@@ -40,6 +40,91 @@ struct media_device_info {
 	__u32 reserved[31];
 };
 
+#define MEDIA_ENT_ID_FLAG_NEXT		(1 << 31)
+
+#define MEDIA_ENT_TYPE_SHIFT		16
+#define MEDIA_ENT_TYPE_MASK		0x00ff0000
+#define MEDIA_ENT_SUBTYPE_MASK		0x0000ffff
+
+#define MEDIA_ENT_T_DEVNODE		(1 << MEDIA_ENT_TYPE_SHIFT)
+#define MEDIA_ENT_T_DEVNODE_V4L		(MEDIA_ENT_T_DEVNODE + 1)
+#define MEDIA_ENT_T_DEVNODE_FB		(MEDIA_ENT_T_DEVNODE + 2)
+#define MEDIA_ENT_T_DEVNODE_ALSA	(MEDIA_ENT_T_DEVNODE + 3)
+#define MEDIA_ENT_T_DEVNODE_DVB		(MEDIA_ENT_T_DEVNODE + 4)
+
+#define MEDIA_ENT_T_V4L2_SUBDEV		(2 << MEDIA_ENT_TYPE_SHIFT)
+#define MEDIA_ENT_T_V4L2_SUBDEV_SENSOR	(MEDIA_ENT_T_V4L2_SUBDEV + 1)
+#define MEDIA_ENT_T_V4L2_SUBDEV_FLASH	(MEDIA_ENT_T_V4L2_SUBDEV + 2)
+#define MEDIA_ENT_T_V4L2_SUBDEV_LENS	(MEDIA_ENT_T_V4L2_SUBDEV + 3)
+
+#define MEDIA_ENT_FL_DEFAULT		(1 << 0)
+
+struct media_entity_desc {
+	__u32 id;
+	char name[32];
+	__u32 type;
+	__u32 revision;
+	__u32 flags;
+	__u32 group_id;
+	__u16 pads;
+	__u16 links;
+
+	__u32 reserved[4];
+
+	union {
+		/* Node specifications */
+		struct {
+			__u32 major;
+			__u32 minor;
+		} v4l;
+		struct {
+			__u32 major;
+			__u32 minor;
+		} fb;
+		struct {
+			__u32 card;
+			__u32 device;
+			__u32 subdevice;
+		} alsa;
+		int dvb;
+
+		/* Sub-device specifications */
+		/* Nothing needed yet */
+		__u8 raw[184];
+	};
+};
+
+#define MEDIA_PAD_FL_SINK		(1 << 0)
+#define MEDIA_PAD_FL_SOURCE		(1 << 1)
+
+struct media_pad_desc {
+	__u32 entity;		/* entity ID */
+	__u16 index;		/* pad index */
+	__u32 flags;		/* pad flags */
+	__u32 reserved[2];
+};
+
+#define MEDIA_LNK_FL_ENABLED		(1 << 0)
+#define MEDIA_LNK_FL_IMMUTABLE		(1 << 1)
+
+struct media_link_desc {
+	struct media_pad_desc source;
+	struct media_pad_desc sink;
+	__u32 flags;
+	__u32 reserved[2];
+};
+
+struct media_links_enum {
+	__u32 entity;
+	/* Should have enough room for pads elements */
+	struct media_pad_desc __user *pads;
+	/* Should have enough room for links elements */
+	struct media_link_desc __user *links;
+	__u32 reserved[4];
+};
+
 #define MEDIA_IOC_DEVICE_INFO		_IOWR('M', 1, struct media_device_info)
+#define MEDIA_IOC_ENUM_ENTITIES		_IOWR('M', 2, struct media_entity_desc)
+#define MEDIA_IOC_ENUM_LINKS		_IOWR('M', 3, struct media_links_enum)
 
 #endif /* __LINUX_MEDIA_H */
diff --git a/include/media/media-entity.h b/include/media/media-entity.h
index a9b31d9..51bdafc 100644
--- a/include/media/media-entity.h
+++ b/include/media/media-entity.h
@@ -24,29 +24,7 @@
 #define _MEDIA_ENTITY_H
 
 #include <linux/list.h>
-
-#define MEDIA_ENT_TYPE_SHIFT		16
-#define MEDIA_ENT_TYPE_MASK		0x00ff0000
-#define MEDIA_ENT_SUBTYPE_MASK		0x0000ffff
-
-#define MEDIA_ENT_T_DEVNODE		(1 << MEDIA_ENT_TYPE_SHIFT)
-#define MEDIA_ENT_T_DEVNODE_V4L		(MEDIA_ENT_T_DEVNODE + 1)
-#define MEDIA_ENT_T_DEVNODE_FB		(MEDIA_ENT_T_DEVNODE + 2)
-#define MEDIA_ENT_T_DEVNODE_ALSA	(MEDIA_ENT_T_DEVNODE + 3)
-#define MEDIA_ENT_T_DEVNODE_DVB		(MEDIA_ENT_T_DEVNODE + 4)
-
-#define MEDIA_ENT_T_V4L2_SUBDEV		(2 << MEDIA_ENT_TYPE_SHIFT)
-#define MEDIA_ENT_T_V4L2_SUBDEV_SENSOR	(MEDIA_ENT_T_V4L2_SUBDEV + 1)
-#define MEDIA_ENT_T_V4L2_SUBDEV_FLASH	(MEDIA_ENT_T_V4L2_SUBDEV + 2)
-#define MEDIA_ENT_T_V4L2_SUBDEV_LENS	(MEDIA_ENT_T_V4L2_SUBDEV + 3)
-
-#define MEDIA_ENT_FL_DEFAULT		(1 << 0)
-
-#define MEDIA_LNK_FL_ENABLED		(1 << 0)
-#define MEDIA_LNK_FL_IMMUTABLE		(1 << 1)
-
-#define MEDIA_PAD_FL_SINK		(1 << 0)
-#define MEDIA_PAD_FL_SOURCE		(1 << 1)
+#include <linux/media.h>
 
 struct media_link {
 	struct media_pad *source;	/* Source pad */