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Add userspace documentation for V4L2 ISP generic parameters and statistics formats. Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com> Reviewed-by: Michael Riesch <michael.riesch@collabora.com> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com> Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com> Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com> Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
68 lines
2.6 KiB
ReStructuredText
68 lines
2.6 KiB
ReStructuredText
.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
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.. _v4l2-isp:
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************************
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Generic V4L2 ISP formats
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************************
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Generic ISP formats are metadata formats that define a mechanism to pass ISP
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parameters and statistics between userspace and drivers in V4L2 buffers. They
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are designed to allow extending them in a backward-compatible way.
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ISP parameters
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==============
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The generic ISP configuration parameters format is realized by a defining a
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single C structure that contains a header, followed by a binary buffer where
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userspace programs a variable number of ISP configuration data block, one for
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each supported ISP feature.
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The :c:type:`v4l2_isp_params_buffer` structure defines the buffer header which
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is followed by a binary buffer of ISP configuration data. Userspace shall
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correctly populate the buffer header with the generic parameters format version
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and with the size (in bytes) of the binary data buffer where it will store the
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ISP blocks configuration.
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Each *ISP configuration block* is preceded by an header implemented by the
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:c:type:`v4l2_isp_params_block_header` structure, followed by the configuration
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parameters for that specific block, defined by the ISP driver specific data
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types.
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Userspace applications are responsible for correctly populating each block's
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header fields (type, flags and size) and the block-specific parameters.
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ISP block enabling, disabling and configuration
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-----------------------------------------------
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When userspace wants to configure and enable an ISP block it shall fully
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populate the block configuration and set the V4L2_ISP_PARAMS_FL_BLOCK_ENABLE
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bit in the block header's `flags` field.
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When userspace simply wants to disable an ISP block the
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V4L2_ISP_PARAMS_FL_BLOCK_DISABLE bit should be set in block header's `flags`
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field. Drivers accept a configuration parameters block with no additional
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data after the header in this case.
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If the configuration of an already active ISP block has to be updated,
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userspace shall fully populate the ISP block parameters and omit setting the
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V4L2_ISP_PARAMS_FL_BLOCK_ENABLE and V4L2_ISP_PARAMS_FL_BLOCK_DISABLE bits in the
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header's `flags` field.
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Setting both the V4L2_ISP_PARAMS_FL_BLOCK_ENABLE and
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V4L2_ISP_PARAMS_FL_BLOCK_DISABLE bits in the flags field is not allowed and
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returns an error.
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Extension to the parameters format can be implemented by adding new blocks
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definition without invalidating the existing ones.
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ISP statistics
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==============
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Support for generic statistics format is not yet implemented in Video4Linux2.
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V4L2 ISP uAPI data types
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========================
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.. kernel-doc:: include/uapi/linux/media/v4l2-isp.h
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