Merge tag 'next-media-rkisp1-20240814' of git://git.kernel.org/pub/scm/linux/kernel/git/pinchartl/linux.git

Extensible parameters support for the rkisp1 driver.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

1 files changed, 48 insertions, 9 deletions

diff --git a/Documentation/userspace-api/media/v4l/metafmt-rkisp1.rst b/Documentation/userspace-api/media/v4l/metafmt-rkisp1.rst
index fa04f00bcd2e..959f6bde8695 100644
--- a/Documentation/userspace-api/media/v4l/metafmt-rkisp1.rst
+++ b/Documentation/userspace-api/media/v4l/metafmt-rkisp1.rst
@@ -1,28 +1,67 @@
 .. SPDX-License-Identifier: GPL-2.0
 
-.. _v4l2-meta-fmt-rk-isp1-params:
-
 .. _v4l2-meta-fmt-rk-isp1-stat-3a:
 
-*****************************************************************************
-V4L2_META_FMT_RK_ISP1_PARAMS ('rk1p'), V4L2_META_FMT_RK_ISP1_STAT_3A ('rk1s')
-*****************************************************************************
+************************************************************************************************************************
+V4L2_META_FMT_RK_ISP1_PARAMS ('rk1p'), V4L2_META_FMT_RK_ISP1_STAT_3A ('rk1s'), V4L2_META_FMT_RK_ISP1_EXT_PARAMS ('rk1e')
+************************************************************************************************************************
 
+========================
 Configuration parameters
 ========================
 
-The configuration parameters are passed to the
+The configuration of the RkISP1 ISP is performed by userspace by providing
+parameters for the ISP to the driver using the :c:type:`v4l2_meta_format`
+interface.
+
+There are two methods that allow to configure the ISP, the `fixed parameters`
+configuration format and the `extensible parameters` configuration
+format.
+
+.. _v4l2-meta-fmt-rk-isp1-params:
+
+Fixed parameters configuration format
+=====================================
+
+When using the fixed configuration format, parameters are passed to the
 :ref:`rkisp1_params <rkisp1_params>` metadata output video node, using
-the :c:type:`v4l2_meta_format` interface. The buffer contains
-a single instance of the C structure :c:type:`rkisp1_params_cfg` defined in
-``rkisp1-config.h``. So the structure can be obtained from the buffer by:
+the `V4L2_META_FMT_RK_ISP1_PARAMS` meta format.
+
+The buffer contains a single instance of the C structure
+:c:type:`rkisp1_params_cfg` defined in ``rkisp1-config.h``. So the structure can
+be obtained from the buffer by:
 
 .. code-block:: c
 
 	struct rkisp1_params_cfg *params = (struct rkisp1_params_cfg*) buffer;
 
+This method supports a subset of the ISP features only, new applications should
+use the extensible parameters method.
+
+.. _v4l2-meta-fmt-rk-isp1-ext-params:
+
+Extensible parameters configuration format
+==========================================
+
+When using the extensible configuration format, parameters are passed to the
+:ref:`rkisp1_params <rkisp1_params>` metadata output video node, using
+the `V4L2_META_FMT_RK_ISP1_EXT_PARAMS` meta format.
+
+The buffer contains a single instance of the C structure
+:c:type:`rkisp1_ext_params_cfg` defined in ``rkisp1-config.h``. The
+:c:type:`rkisp1_ext_params_cfg` structure is designed to allow userspace to
+populate the data buffer with only the configuration data for the ISP blocks it
+intends to configure. The extensible parameters format design allows developers
+to define new block types to support new configuration parameters, and defines a
+versioning scheme so that it can be extended and versioned without breaking
+compatibility with existing applications.
+
+For these reasons, this configuration method is preferred over the `fixed
+parameters` format alternative.
+
 .. rkisp1_stat_buffer
 
+===========================
 3A and histogram statistics
 ===========================