[libcamera-devel,v3,2/5] media: media.h: Add new media link type

15399 diff mbox series

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>
---

Changes since v1:

	- None

changes since the rfc:

	- Split out into its own patch (mostly so it can be followed by patch
	#3, which corrects some media-core code that is otherwise broken by the
	new links)

 .../media/mediactl/media-controller-model.rst   |  6 ++++++
 .../media/mediactl/media-types.rst              | 17 ++++++++++++-----
 include/uapi/linux/media.h                      |  1 +
 3 files changed, 19 insertions(+), 5 deletions(-)

Hi !

Thanks for the patch !

On 02/03/2022 23:03, Daniel Scally wrote:
> 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>
> ---
> 
> Changes since v1:
> 
> 	- None
> 
> changes since the rfc:
> 
> 	- Split out into its own patch (mostly so it can be followed by patch
> 	#3, which corrects some media-core code that is otherwise broken by the
> 	new links)
> 
>   .../media/mediactl/media-controller-model.rst   |  6 ++++++
>   .../media/mediactl/media-types.rst              | 17 ++++++++++++-----
>   include/uapi/linux/media.h                      |  1 +
>   3 files changed, 19 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/userspace-api/media/mediactl/media-controller-model.rst b/Documentation/userspace-api/media/mediactl/media-controller-model.rst
> index 222cb99debb5..78bfdfb2a322 100644
> --- 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 0a26397bd01d..60747251d409 100644
> --- 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 ummutable, so
> +     applications must not assume either case.
> \ No newline at end of file
> diff --git a/include/uapi/linux/media.h b/include/uapi/linux/media.h
> index 200fa8462b90..afbae7213d35 100644
> --- 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;