media: media.h: Add new media link type

To describe in the kernel the connection between devices and their
supporting peripherals (for example, a camera sensor and the vcm
driving the focusing lens for it), add a new type of media link
to introduce the concept of these ancillary links.

Add some elements to the uAPI documentation to explain the new link
type, their purpose and some aspects of their current implementation.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Scally <djrscally@gmail.com>
Reviewed-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

diff --git a/Documentation/userspace-api/media/mediactl/media-controller-model.rst b/Documentation/userspace-api/media/mediactl/media-controller-model.rst
index 222cb99debb52859427c424136294db3b640d1d9..78bfdfb2a322fe64d5ac150be311c6e287db36fe 100644 (file)
--- a/Documentation/userspace-api/media/mediactl/media-controller-model.rst
+++ b/Documentation/userspace-api/media/mediactl/media-controller-model.rst
@@ -33,3 +33,9 @@ are:
 
 -  An **interface link** is a point-to-point bidirectional control
    connection between a Linux Kernel interface and an entity.
+
+- An **ancillary link** is a point-to-point connection denoting that two
+  entities form a single logical unit. For example this could represent the
+  fact that a particular camera sensor and lens controller form a single
+  physical module, meaning this lens controller drives the lens for this
+  camera sensor.
\ No newline at end of file

diff --git a/Documentation/userspace-api/media/mediactl/media-types.rst b/Documentation/userspace-api/media/mediactl/media-types.rst
index 0a26397bd01d65526dd4899fa699c7cd936fbd93..0ffeece1e0c8e94c3b25185b1de5ccc15350db52 100644 (file)
--- a/Documentation/userspace-api/media/mediactl/media-types.rst
+++ b/Documentation/userspace-api/media/mediactl/media-types.rst
@@ -412,14 +412,21 @@ must be set for every pad.
          is set by drivers and is read-only for applications.
 
     *  -  ``MEDIA_LNK_FL_LINK_TYPE``
-       -  This is a bitmask that defines the type of the link. Currently,
-         two types of links are supported:
+       -  This is a bitmask that defines the type of the link. The following
+         link types are currently supported:
 
          .. _MEDIA-LNK-FL-DATA-LINK:
 
-         ``MEDIA_LNK_FL_DATA_LINK`` if the link is between two pads
+         ``MEDIA_LNK_FL_DATA_LINK`` for links that represent a data connection
+         between two pads.
 
          .. _MEDIA-LNK-FL-INTERFACE-LINK:
 
-         ``MEDIA_LNK_FL_INTERFACE_LINK`` if the link is between an
-         interface and an entity
+         ``MEDIA_LNK_FL_INTERFACE_LINK`` for links that associate an entity to its
+         interface.
+
+         .. _MEDIA-LNK-FL-ANCILLARY-LINK:
+
+         ``MEDIA_LNK_FL_ANCILLARY_LINK`` for links that represent a physical
+         relationship between two entities. The link may or may not be
+         immutable, so applications must not assume either case.

diff --git a/include/uapi/linux/media.h b/include/uapi/linux/media.h
index 200fa8462b90ce29181bb3fc381a2280d7859f6d..afbae7213d35f26fb6213ac738f4d94a6724925a 100644 (file)
--- a/include/uapi/linux/media.h
+++ b/include/uapi/linux/media.h
@@ -226,6 +226,7 @@ struct media_pad_desc {
 #define MEDIA_LNK_FL_LINK_TYPE                 (0xf << 28)
 #  define MEDIA_LNK_FL_DATA_LINK               (0 << 28)
 #  define MEDIA_LNK_FL_INTERFACE_LINK          (1 << 28)
+#  define MEDIA_LNK_FL_ANCILLARY_LINK          (2 << 28)
 
 struct media_link_desc {
        struct media_pad_desc source;