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1.. SPDX-License-Identifier: GPL-2.0-only2 3.. include:: <isonum.txt>4 5.. _media-ccs-uapi:6 7MIPI CCS camera sensor driver8=============================9 10The MIPI CCS camera sensor driver is a generic driver for `MIPI CCS11<https://www.mipi.org/specifications/camera-command-set>`_ compliant12camera sensors. It exposes three sub-devices representing the pixel array,13the binner and the scaler.14 15As the capabilities of individual devices vary, the driver exposes16interfaces based on the capabilities that exist in hardware.17 18Also see :ref:`the CCS driver kernel documentation <media-ccs-driver>`.19 20Pixel Array sub-device21----------------------22 23The pixel array sub-device represents the camera sensor's pixel matrix, as well24as analogue crop functionality present in many compliant devices. The analogue25crop is configured using the ``V4L2_SEL_TGT_CROP`` on the source pad (0) of the26entity. The size of the pixel matrix can be obtained by getting the27``V4L2_SEL_TGT_NATIVE_SIZE`` target.28 29Binner30------31 32The binner sub-device represents the binning functionality on the sensor. For33that purpose, selection target ``V4L2_SEL_TGT_COMPOSE`` is supported on the34sink pad (0).35 36Additionally, if a device has no scaler or digital crop functionality, the37source pad (1) exposes another digital crop selection rectangle that can only38crop at the end of the lines and frames.39 40Scaler41------42 43The scaler sub-device represents the digital crop and scaling functionality of44the sensor. The V4L2 selection target ``V4L2_SEL_TGT_CROP`` is used to45configure the digital crop on the sink pad (0) when digital crop is supported.46Scaling is configured using selection target ``V4L2_SEL_TGT_COMPOSE`` on the47sink pad (0) as well.48 49Additionally, if the scaler sub-device exists, its source pad (1) exposes50another digital crop selection rectangle that can only crop at the end of the51lines and frames.52 53Digital and analogue crop54-------------------------55 56Digital crop functionality is referred to as cropping that effectively works by57dropping some data on the floor. Analogue crop, on the other hand, means that58the cropped information is never retrieved. In case of camera sensors, the59analogue data is never read from the pixel matrix that are outside the60configured selection rectangle that designates crop. The difference has an61effect in device timing and likely also in power consumption.62 63Private controls64----------------65 66The MIPI CCS driver implements a number of private controls under67``V4L2_CID_USER_BASE_CCS`` to control the MIPI CCS compliant camera sensors.68 69Analogue gain model70~~~~~~~~~~~~~~~~~~~71 72The CCS defines an analogue gain model where the gain can be calculated using73the following formula:74 75 gain = m0 * x + c0 / (m1 * x + c1)76 77Either m0 or c0 will be zero. The constants that are device specific, can be78obtained from the following controls:79 80 V4L2_CID_CCS_ANALOGUE_GAIN_M081 V4L2_CID_CCS_ANALOGUE_GAIN_M182 V4L2_CID_CCS_ANALOGUE_GAIN_C083 V4L2_CID_CCS_ANALOGUE_GAIN_C184 85The analogue gain (``x`` in the formula) is controlled through86``V4L2_CID_ANALOGUE_GAIN`` in this case.87 88Alternate analogue gain model89~~~~~~~~~~~~~~~~~~~~~~~~~~~~~90 91The CCS defines another analogue gain model called alternate analogue gain. In92this case, the formula to calculate actual gain consists of linear and93exponential parts:94 95 gain = linear * 2 ^ exponent96 97The ``linear`` and ``exponent`` factors can be set using the98``V4L2_CID_CCS_ANALOGUE_LINEAR_GAIN`` and99``V4L2_CID_CCS_ANALOGUE_EXPONENTIAL_GAIN`` controls, respectively100 101Shading correction102~~~~~~~~~~~~~~~~~~103 104The CCS standard supports lens shading correction. The feature can be controlled105using ``V4L2_CID_CCS_SHADING_CORRECTION``. Additionally, the luminance106correction level may be changed using107``V4L2_CID_CCS_LUMINANCE_CORRECTION_LEVEL``, where value 0 indicates no108correction and 128 indicates correcting the luminance in corners to 10 % less109than in the centre.110 111Shading correction needs to be enabled for luminance correction level to have an112effect.113 114**Copyright** |copy| 2020 Intel Corporation115