1 .. SPDX-License-Identifier: GPL-2.0-only 2 3 .. include:: <isonum.txt> 4 5 .. _media-ccs-uapi: 6 7 MIPI CCS camera sensor driver 8 ============================= 9 10 The MIPI CCS camera sensor driver is a generic driver for `MIPI CCS 11 <https://www.mipi.org/specifications/camera-command-set>`_ compliant 12 camera sensors. It exposes three sub-devices representing the pixel array, 13 the binner and the scaler. 14 15 As the capabilities of individual devices vary, the driver exposes 16 interfaces based on the capabilities that exist in hardware. 17 18 Also see :ref:`the CCS driver kernel documentation <media-ccs-driver>`. 19 20 Pixel Array sub-device 21 ---------------------- 22 23 The pixel array sub-device represents the camera sensor's pixel matrix, as well 24 as analogue crop functionality present in many compliant devices. The analogue 25 crop is configured using the ``V4L2_SEL_TGT_CROP`` on the source pad (0) of the 26 entity. The size of the pixel matrix can be obtained by getting the 27 ``V4L2_SEL_TGT_NATIVE_SIZE`` target. 28 29 Binner 30 ------ 31 32 The binner sub-device represents the binning functionality on the sensor. For 33 that purpose, selection target ``V4L2_SEL_TGT_COMPOSE`` is supported on the 34 sink pad (0). 35 36 Additionally, if a device has no scaler or digital crop functionality, the 37 source pad (1) exposes another digital crop selection rectangle that can only 38 crop at the end of the lines and frames. 39 40 Scaler 41 ------ 42 43 The scaler sub-device represents the digital crop and scaling functionality of 44 the sensor. The V4L2 selection target ``V4L2_SEL_TGT_CROP`` is used to 45 configure the digital crop on the sink pad (0) when digital crop is supported. 46 Scaling is configured using selection target ``V4L2_SEL_TGT_COMPOSE`` on the 47 sink pad (0) as well. 48 49 Additionally, if the scaler sub-device exists, its source pad (1) exposes 50 another digital crop selection rectangle that can only crop at the end of the 51 lines and frames. 52 53 Digital and analogue crop 54 ------------------------- 55 56 Digital crop functionality is referred to as cropping that effectively works by 57 dropping some data on the floor. Analogue crop, on the other hand, means that 58 the cropped information is never retrieved. In case of camera sensors, the 59 analogue data is never read from the pixel matrix that are outside the 60 configured selection rectangle that designates crop. The difference has an 61 effect in device timing and likely also in power consumption. 62 63 Private controls 64 ---------------- 65 66 The MIPI CCS driver implements a number of private controls under 67 ``V4L2_CID_USER_BASE_CCS`` to control the MIPI CCS compliant camera sensors. 68 69 Analogue gain model 70 ~~~~~~~~~~~~~~~~~~~ 71 72 The CCS defines an analogue gain model where the gain can be calculated using 73 the following formula: 74 75 gain = m0 * x + c0 / (m1 * x + c1) 76 77 Either m0 or c0 will be zero. The constants that are device specific, can be 78 obtained from the following controls: 79 80 V4L2_CID_CCS_ANALOGUE_GAIN_M0 81 V4L2_CID_CCS_ANALOGUE_GAIN_M1 82 V4L2_CID_CCS_ANALOGUE_GAIN_C0 83 V4L2_CID_CCS_ANALOGUE_GAIN_C1 84 85 The analogue gain (``x`` in the formula) is controlled through 86 ``V4L2_CID_ANALOGUE_GAIN`` in this case. 87 88 Alternate analogue gain model 89 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 90 91 The CCS defines another analogue gain model called alternate analogue gain. In 92 this case, the formula to calculate actual gain consists of linear and 93 exponential parts: 94 95 gain = linear * 2 ^ exponent 96 97 The ``linear`` and ``exponent`` factors can be set using the 98 ``V4L2_CID_CCS_ANALOGUE_LINEAR_GAIN`` and 99 ``V4L2_CID_CCS_ANALOGUE_EXPONENTIAL_GAIN`` controls, respectively 100 101 Shading correction 102 ~~~~~~~~~~~~~~~~~~ 103 104 The CCS standard supports lens shading correction. The feature can be controlled 105 using ``V4L2_CID_CCS_SHADING_CORRECTION``. Additionally, the luminance 106 correction level may be changed using 107 ``V4L2_CID_CCS_LUMINANCE_CORRECTION_LEVEL``, where value 0 indicates no 108 correction and 128 indicates correcting the luminance in corners to 10 % less 109 than in the centre. 110 111 Shading correction needs to be enabled for luminance correction level to have an 112 effect. 113 114 **Copyright** |copy| 2020 Intel Corporation
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