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- .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
- .. _v4l2-isp:
- ************************
- Generic V4L2 ISP formats
- ************************
- Generic ISP formats are metadata formats that define a mechanism to pass ISP
- parameters and statistics between userspace and drivers in V4L2 buffers. They
- are designed to allow extending them in a backward-compatible way.
- ISP parameters
- ==============
- The generic ISP configuration parameters format is realized by a defining a
- single C structure that contains a header, followed by a binary buffer where
- userspace programs a variable number of ISP configuration data block, one for
- each supported ISP feature.
- The :c:type:`v4l2_isp_params_buffer` structure defines the buffer header which
- is followed by a binary buffer of ISP configuration data. Userspace shall
- correctly populate the buffer header with the generic parameters format version
- and with the size (in bytes) of the binary data buffer where it will store the
- ISP blocks configuration.
- Each *ISP configuration block* is preceded by an header implemented by the
- :c:type:`v4l2_isp_params_block_header` structure, followed by the configuration
- parameters for that specific block, defined by the ISP driver specific data
- types.
- Userspace applications are responsible for correctly populating each block's
- header fields (type, flags and size) and the block-specific parameters.
- ISP block enabling, disabling and configuration
- -----------------------------------------------
- When userspace wants to configure and enable an ISP block it shall fully
- populate the block configuration and set the V4L2_ISP_PARAMS_FL_BLOCK_ENABLE
- bit in the block header's `flags` field.
- When userspace simply wants to disable an ISP block the
- V4L2_ISP_PARAMS_FL_BLOCK_DISABLE bit should be set in block header's `flags`
- field. Drivers accept a configuration parameters block with no additional
- data after the header in this case.
- If the configuration of an already active ISP block has to be updated,
- userspace shall fully populate the ISP block parameters and omit setting the
- V4L2_ISP_PARAMS_FL_BLOCK_ENABLE and V4L2_ISP_PARAMS_FL_BLOCK_DISABLE bits in the
- header's `flags` field.
- Setting both the V4L2_ISP_PARAMS_FL_BLOCK_ENABLE and
- V4L2_ISP_PARAMS_FL_BLOCK_DISABLE bits in the flags field is not allowed and
- returns an error.
- Extension to the parameters format can be implemented by adding new blocks
- definition without invalidating the existing ones.
- ISP statistics
- ==============
- Support for generic statistics format is not yet implemented in Video4Linux2.
- V4L2 ISP uAPI data types
- ========================
- .. kernel-doc:: include/uapi/linux/media/v4l2-isp.h
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