96 lines
3.5 KiB
ReStructuredText
96 lines
3.5 KiB
ReStructuredText
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.. SPDX-License-Identifier: GPL-2.0-only OR BSD-3-Clause
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.. include:: <isonum.txt>
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MIPI CCS camera sensor driver
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=============================
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The MIPI CCS camera sensor driver is a generic driver for `MIPI CCS
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<https://www.mipi.org/specifications/camera-command-set>`_ compliant
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camera sensors. It exposes three sub-devices representing the pixel array,
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the binner and the scaler.
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As the capabilities of individual devices vary, the driver exposes
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interfaces based on the capabilities that exist in hardware.
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Pixel Array sub-device
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----------------------
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The pixel array sub-device represents the camera sensor's pixel matrix, as well
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as analogue crop functionality present in many compliant devices. The analogue
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crop is configured using the ``V4L2_SEL_TGT_CROP`` on the source pad (0) of the
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entity. The size of the pixel matrix can be obtained by getting the
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``V4L2_SEL_TGT_NATIVE_SIZE`` target.
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Binner
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------
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The binner sub-device represents the binning functionality on the sensor. For
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that purpose, selection target ``V4L2_SEL_TGT_COMPOSE`` is supported on the
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sink pad (0).
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Additionally, if a device has no scaler or digital crop functionality, the
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source pad (1) expses another digital crop selection rectangle that can only
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crop at the end of the lines and frames.
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Scaler
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------
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The scaler sub-device represents the digital crop and scaling functionality of
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the sensor. The V4L2 selection target ``V4L2_SEL_TGT_CROP`` is used to
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configure the digital crop on the sink pad (0) when digital crop is supported.
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Scaling is configured using selection target ``V4L2_SEL_TGT_COMPOSE`` on the
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sink pad (0) as well.
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Additionally, if the scaler sub-device exists, its source pad (1) exposes
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another digital crop selection rectangle that can only crop at the end of the
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lines and frames.
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Digital and analogue crop
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-------------------------
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Digital crop functionality is referred to as cropping that effectively works by
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dropping some data on the floor. Analogue crop, on the other hand, means that
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the cropped information is never retrieved. In case of camera sensors, the
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analogue data is never read from the pixel matrix that are outside the
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configured selection rectangle that designates crop. The difference has an
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effect in device timing and likely also in power consumption.
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Register definition generator
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-----------------------------
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The ccs-regs.asc file contains MIPI CCS register definitions that are used
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to produce C source code files for definitions that can be better used by
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programs written in C language. As there are many dependencies between the
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produced files, please do not modify them manually as it's error-prone and
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in vain, but instead change the script producing them.
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Usage
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~~~~~
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Conventionally the script is called this way to update the CCS driver
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definitions:
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.. code-block:: none
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$ Documentation/driver-api/media/drivers/ccs/mk-ccs-regs -k \
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-e drivers/media/i2c/ccs/ccs-regs.h \
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-L drivers/media/i2c/ccs/ccs-limits.h \
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-l drivers/media/i2c/ccs/ccs-limits.c \
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-c Documentation/driver-api/media/drivers/ccs/ccs-regs.asc
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CCS PLL calculator
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==================
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The CCS PLL calculator is used to compute the PLL configuration, given sensor's
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capabilities as well as board configuration and user specified configuration. As
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the configuration space that encompasses all these configurations is vast, the
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PLL calculator isn't entirely trivial. Yet it is relatively simple to use for a
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driver.
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The PLL model implemented by the PLL calculator corresponds to MIPI CCS 1.1.
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.. kernel-doc:: drivers/media/i2c/ccs-pll.h
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**Copyright** |copy| 2020 Intel Corporation
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