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1.. Permission is granted to copy, distribute and/or modify this
2.. document under the terms of the GNU Free Documentation License,
3.. Version 1.1 or any later version published by the Free Software
4.. Foundation, with no Invariant Sections, no Front-Cover Texts
5.. and no Back-Cover Texts. A copy of the license is included at
6.. Documentation/media/uapi/fdl-appendix.rst.
7..
8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
9
10.. _dv-controls:
11
12*******************************
13Digital Video Control Reference
14*******************************
15
16The Digital Video control class is intended to control receivers and
17transmitters for `VGA <http://en.wikipedia.org/wiki/Vga>`__,
18`DVI <http://en.wikipedia.org/wiki/Digital_Visual_Interface>`__
19(Digital Visual Interface), HDMI (:ref:`hdmi`) and DisplayPort
20(:ref:`dp`). These controls are generally expected to be private to
21the receiver or transmitter subdevice that implements them, so they are
22only exposed on the ``/dev/v4l-subdev*`` device node.
23
24.. note::
25
26 Note that these devices can have multiple input or output pads which are
27 hooked up to e.g. HDMI connectors. Even though the subdevice will
28 receive or transmit video from/to only one of those pads, the other pads
29 can still be active when it comes to EDID (Extended Display
30 Identification Data, :ref:`vesaedid`) and HDCP (High-bandwidth Digital
31 Content Protection System, :ref:`hdcp`) processing, allowing the
32 device to do the fairly slow EDID/HDCP handling in advance. This allows
33 for quick switching between connectors.
34
35These pads appear in several of the controls in this section as
36bitmasks, one bit for each pad. Bit 0 corresponds to pad 0, bit 1 to pad
371, etc. The maximum value of the control is the set of valid pads.
38
39
40.. _dv-control-id:
41
42Digital Video Control IDs
43=========================
44
45``V4L2_CID_DV_CLASS (class)``
46 The Digital Video class descriptor.
47
48``V4L2_CID_DV_TX_HOTPLUG (bitmask)``
49 Many connectors have a hotplug pin which is high if EDID information
50 is available from the source. This control shows the state of the
51 hotplug pin as seen by the transmitter. Each bit corresponds to an
52 output pad on the transmitter. If an output pad does not have an
53 associated hotplug pin, then the bit for that pad will be 0. This
54 read-only control is applicable to DVI-D, HDMI and DisplayPort
55 connectors.
56
57``V4L2_CID_DV_TX_RXSENSE (bitmask)``
58 Rx Sense is the detection of pull-ups on the TMDS clock lines. This
59 normally means that the sink has left/entered standby (i.e. the
60 transmitter can sense that the receiver is ready to receive video).
61 Each bit corresponds to an output pad on the transmitter. If an
62 output pad does not have an associated Rx Sense, then the bit for
63 that pad will be 0. This read-only control is applicable to DVI-D
64 and HDMI devices.
65
66``V4L2_CID_DV_TX_EDID_PRESENT (bitmask)``
67 When the transmitter sees the hotplug signal from the receiver it
68 will attempt to read the EDID. If set, then the transmitter has read
69 at least the first block (= 128 bytes). Each bit corresponds to an
70 output pad on the transmitter. If an output pad does not support
71 EDIDs, then the bit for that pad will be 0. This read-only control
72 is applicable to VGA, DVI-A/D, HDMI and DisplayPort connectors.
73
74``V4L2_CID_DV_TX_MODE``
75 (enum)
76
77enum v4l2_dv_tx_mode -
78 HDMI transmitters can transmit in DVI-D mode (just video) or in HDMI
79 mode (video + audio + auxiliary data). This control selects which
80 mode to use: V4L2_DV_TX_MODE_DVI_D or V4L2_DV_TX_MODE_HDMI.
81 This control is applicable to HDMI connectors.
82
83``V4L2_CID_DV_TX_RGB_RANGE``
84 (enum)
85
86enum v4l2_dv_rgb_range -
87 Select the quantization range for RGB output. V4L2_DV_RANGE_AUTO
88 follows the RGB quantization range specified in the standard for the
89 video interface (ie. :ref:`cea861` for HDMI).
90 V4L2_DV_RANGE_LIMITED and V4L2_DV_RANGE_FULL override the
91 standard to be compatible with sinks that have not implemented the
92 standard correctly (unfortunately quite common for HDMI and DVI-D).
93 Full range allows all possible values to be used whereas limited
94 range sets the range to (16 << (N-8)) - (235 << (N-8)) where N is
95 the number of bits per component. This control is applicable to VGA,
96 DVI-A/D, HDMI and DisplayPort connectors.
97
98``V4L2_CID_DV_TX_IT_CONTENT_TYPE``
99 (enum)
100
101enum v4l2_dv_it_content_type -
102 Configures the IT Content Type of the transmitted video. This
103 information is sent over HDMI and DisplayPort connectors as part of
104 the AVI InfoFrame. The term 'IT Content' is used for content that
105 originates from a computer as opposed to content from a TV broadcast
106 or an analog source. The enum v4l2_dv_it_content_type defines
107 the possible content types:
108
109.. tabularcolumns:: |p{7.3cm}|p{10.4cm}|
110
111.. flat-table::
112 :header-rows: 0
113 :stub-columns: 0
114
115 * - ``V4L2_DV_IT_CONTENT_TYPE_GRAPHICS``
116 - Graphics content. Pixel data should be passed unfiltered and
117 without analog reconstruction.
118 * - ``V4L2_DV_IT_CONTENT_TYPE_PHOTO``
119 - Photo content. The content is derived from digital still pictures.
120 The content should be passed through with minimal scaling and
121 picture enhancements.
122 * - ``V4L2_DV_IT_CONTENT_TYPE_CINEMA``
123 - Cinema content.
124 * - ``V4L2_DV_IT_CONTENT_TYPE_GAME``
125 - Game content. Audio and video latency should be minimized.
126 * - ``V4L2_DV_IT_CONTENT_TYPE_NO_ITC``
127 - No IT Content information is available and the ITC bit in the AVI
128 InfoFrame is set to 0.
129
130
131
132``V4L2_CID_DV_RX_POWER_PRESENT (bitmask)``
133 Detects whether the receiver receives power from the source (e.g.
134 HDMI carries 5V on one of the pins). This is often used to power an
135 eeprom which contains EDID information, such that the source can
136 read the EDID even if the sink is in standby/power off. Each bit
137 corresponds to an input pad on the receiver. If an input pad
138 cannot detect whether power is present, then the bit for that pad
139 will be 0. This read-only control is applicable to DVI-D, HDMI and
140 DisplayPort connectors.
141
142``V4L2_CID_DV_RX_RGB_RANGE``
143 (enum)
144
145enum v4l2_dv_rgb_range -
146 Select the quantization range for RGB input. V4L2_DV_RANGE_AUTO
147 follows the RGB quantization range specified in the standard for the
148 video interface (ie. :ref:`cea861` for HDMI).
149 V4L2_DV_RANGE_LIMITED and V4L2_DV_RANGE_FULL override the
150 standard to be compatible with sources that have not implemented the
151 standard correctly (unfortunately quite common for HDMI and DVI-D).
152 Full range allows all possible values to be used whereas limited
153 range sets the range to (16 << (N-8)) - (235 << (N-8)) where N is
154 the number of bits per component. This control is applicable to VGA,
155 DVI-A/D, HDMI and DisplayPort connectors.
156
157``V4L2_CID_DV_RX_IT_CONTENT_TYPE``
158 (enum)
159
160enum v4l2_dv_it_content_type -
161 Reads the IT Content Type of the received video. This information is
162 sent over HDMI and DisplayPort connectors as part of the AVI
163 InfoFrame. The term 'IT Content' is used for content that originates
164 from a computer as opposed to content from a TV broadcast or an
165 analog source. See ``V4L2_CID_DV_TX_IT_CONTENT_TYPE`` for the
166 available content types.