1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2
3 .. _dv-controls:
4
5 *******************************
6 Digital Video Control Reference
7 *******************************
8
9 The Digital Video control class is intended to control receivers and
10 transmitters for `VGA <http://en.wikipedia.org/wiki/Vga>`__,
11 `DVI <http://en.wikipedia.org/wiki/Digital_Visual_Interface>`__
12 (Digital Visual Interface), HDMI (:ref:`hdmi`) and DisplayPort
13 (:ref:`dp`). These controls are generally expected to be private to
14 the receiver or transmitter subdevice that implements them, so they are
15 only exposed on the ``/dev/v4l-subdev*`` device node.
16
17 .. note::
18
19 Note that these devices can have multiple input or output pads which are
20 hooked up to e.g. HDMI connectors. Even though the subdevice will
21 receive or transmit video from/to only one of those pads, the other pads
22 can still be active when it comes to EDID (Extended Display
23 Identification Data, :ref:`vesaedid`) and HDCP (High-bandwidth Digital
24 Content Protection System, :ref:`hdcp`) processing, allowing the
25 device to do the fairly slow EDID/HDCP handling in advance. This allows
26 for quick switching between connectors.
27
28 These pads appear in several of the controls in this section as
29 bitmasks, one bit for each pad. Bit 0 corresponds to pad 0, bit 1 to pad
30 1, etc. The maximum value of the control is the set of valid pads.
31
32
33 .. _dv-control-id:
34
35 Digital Video Control IDs
36 =========================
37
38 ``V4L2_CID_DV_CLASS (class)``
39 The Digital Video class descriptor.
40
41 ``V4L2_CID_DV_TX_HOTPLUG (bitmask)``
42 Many connectors have a hotplug pin which is high if EDID information
43 is available from the source. This control shows the state of the
44 hotplug pin as seen by the transmitter. Each bit corresponds to an
45 output pad on the transmitter. If an output pad does not have an
46 associated hotplug pin, then the bit for that pad will be 0. This
47 read-only control is applicable to DVI-D, HDMI and DisplayPort
48 connectors.
49
50 ``V4L2_CID_DV_TX_RXSENSE (bitmask)``
51 Rx Sense is the detection of pull-ups on the TMDS clock lines. This
52 normally means that the sink has left/entered standby (i.e. the
53 transmitter can sense that the receiver is ready to receive video).
54 Each bit corresponds to an output pad on the transmitter. If an
55 output pad does not have an associated Rx Sense, then the bit for
56 that pad will be 0. This read-only control is applicable to DVI-D
57 and HDMI devices.
58
59 ``V4L2_CID_DV_TX_EDID_PRESENT (bitmask)``
60 When the transmitter sees the hotplug signal from the receiver it
61 will attempt to read the EDID. If set, then the transmitter has read
62 at least the first block (= 128 bytes). Each bit corresponds to an
63 output pad on the transmitter. If an output pad does not support
64 EDIDs, then the bit for that pad will be 0. This read-only control
65 is applicable to VGA, DVI-A/D, HDMI and DisplayPort connectors.
66
67 ``V4L2_CID_DV_TX_MODE``
68 (enum)
69
70 enum v4l2_dv_tx_mode -
71 HDMI transmitters can transmit in DVI-D mode (just video) or in HDMI
72 mode (video + audio + auxiliary data). This control selects which
73 mode to use: V4L2_DV_TX_MODE_DVI_D or V4L2_DV_TX_MODE_HDMI.
74 This control is applicable to HDMI connectors.
75
76 ``V4L2_CID_DV_TX_RGB_RANGE``
77 (enum)
78
79 enum v4l2_dv_rgb_range -
80 Select the quantization range for RGB output. V4L2_DV_RANGE_AUTO
81 follows the RGB quantization range specified in the standard for the
82 video interface (ie. :ref:`cea861` for HDMI).
83 V4L2_DV_RANGE_LIMITED and V4L2_DV_RANGE_FULL override the
84 standard to be compatible with sinks that have not implemented the
85 standard correctly (unfortunately quite common for HDMI and DVI-D).
86 Full range allows all possible values to be used whereas limited
87 range sets the range to (16 << (N-8)) - (235 << (N-8)) where N is
88 the number of bits per component. This control is applicable to VGA,
89 DVI-A/D, HDMI and DisplayPort connectors.
90
91 ``V4L2_CID_DV_TX_IT_CONTENT_TYPE``
92 (enum)
93
94 enum v4l2_dv_it_content_type -
95 Configures the IT Content Type of the transmitted video. This
96 information is sent over HDMI and DisplayPort connectors as part of
97 the AVI InfoFrame. The term 'IT Content' is used for content that
98 originates from a computer as opposed to content from a TV broadcast
99 or an analog source. The enum v4l2_dv_it_content_type defines
100 the possible content types:
101
102 .. tabularcolumns:: |p{7.3cm}|p{10.2cm}|
103
104 .. flat-table::
105 :header-rows: 0
106 :stub-columns: 0
107
108 * - ``V4L2_DV_IT_CONTENT_TYPE_GRAPHICS``
109 - Graphics content. Pixel data should be passed unfiltered and
110 without analog reconstruction.
111 * - ``V4L2_DV_IT_CONTENT_TYPE_PHOTO``
112 - Photo content. The content is derived from digital still pictures.
113 The content should be passed through with minimal scaling and
114 picture enhancements.
115 * - ``V4L2_DV_IT_CONTENT_TYPE_CINEMA``
116 - Cinema content.
117 * - ``V4L2_DV_IT_CONTENT_TYPE_GAME``
118 - Game content. Audio and video latency should be minimized.
119 * - ``V4L2_DV_IT_CONTENT_TYPE_NO_ITC``
120 - No IT Content information is available and the ITC bit in the AVI
121 InfoFrame is set to 0.
122
123
124
125 ``V4L2_CID_DV_RX_POWER_PRESENT (bitmask)``
126 Detects whether the receiver receives power from the source (e.g.
127 HDMI carries 5V on one of the pins). This is often used to power an
128 eeprom which contains EDID information, such that the source can
129 read the EDID even if the sink is in standby/power off. Each bit
130 corresponds to an input pad on the receiver. If an input pad
131 cannot detect whether power is present, then the bit for that pad
132 will be 0. This read-only control is applicable to DVI-D, HDMI and
133 DisplayPort connectors.
134
135 ``V4L2_CID_DV_RX_RGB_RANGE``
136 (enum)
137
138 enum v4l2_dv_rgb_range -
139 Select the quantization range for RGB input. V4L2_DV_RANGE_AUTO
140 follows the RGB quantization range specified in the standard for the
141 video interface (ie. :ref:`cea861` for HDMI).
142 V4L2_DV_RANGE_LIMITED and V4L2_DV_RANGE_FULL override the
143 standard to be compatible with sources that have not implemented the
144 standard correctly (unfortunately quite common for HDMI and DVI-D).
145 Full range allows all possible values to be used whereas limited
146 range sets the range to (16 << (N-8)) - (235 << (N-8)) where N is
147 the number of bits per component. This control is applicable to VGA,
148 DVI-A/D, HDMI and DisplayPort connectors.
149
150 ``V4L2_CID_DV_RX_IT_CONTENT_TYPE``
151 (enum)
152
153 enum v4l2_dv_it_content_type -
154 Reads the IT Content Type of the received video. This information is
155 sent over HDMI and DisplayPort connectors as part of the AVI
156 InfoFrame. The term 'IT Content' is used for content that originates
157 from a computer as opposed to content from a TV broadcast or an
158 analog source. See ``V4L2_CID_DV_TX_IT_CONTENT_TYPE`` for the
159 available content types.
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.