[PATCH v6 09/28] media: Documentation: Document embedded data guidelines for camera sensors

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Document how embedded data support should be implemented for camera
sensors, and when and how CCS embedded data format should be referenced.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
---
 .../media/drivers/camera-sensor.rst           | 28 +++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/Documentation/userspace-api/media/drivers/camera-sensor.rst b/Documentation/userspace-api/media/drivers/camera-sensor.rst
index 919a50e8b9d9..308f391c5ca1 100644
--- a/Documentation/userspace-api/media/drivers/camera-sensor.rst
+++ b/Documentation/userspace-api/media/drivers/camera-sensor.rst
@@ -102,3 +102,31 @@ register programming sequences shall initialize the :ref:`V4L2_CID_HFLIP
 values programmed by the register sequences. The default values of these
 controls shall be 0 (disabled). Especially these controls shall not be inverted,
 independently of the sensor's mounting rotation.
+
+Embedded data
+-------------
+
+Many sensors, mostly raw sensors, support embedded data which is used to convey
+the sensor configuration for the captured frame back to the host. While CSI-2 is
+the most common bus used by such sensors, embedded data is not entirely limited
+to CSI-2 bus due to e.g. bridge devices.
+
+Embedded data support should use an internal source pad and route to the
+external pad. If embedded data output can be disabled in hardware, it should be
+possible to disable the embedded data route via ``VIDIOC_SUBDEV_S_ROUTING``
+IOCTL.
+
+In general, changing the embedded data format from the driver-configured values
+is not supported. The height of the metadata is hardware specific and the width
+is that (or less of that) of the image width, as configured on the pixel data
+stream.
+
+CCS and non-CCS embedded data
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Embedded data which is compliant with CCS definitions shall use ``CCS embedded
+data format <MEDIA-BUS-FMT-CCS-EMBEDDED>``. Device specific embedded data which
+is compliant up to MIPI CCS embedded data levels 1 or 2 only shall refer to CCS
+embedded data formats and document the level of conformance. The rest of the
+device specific embedded data format shall be documented in the context of the
+data format itself.
-- 
2.39.2