Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2.. c:namespace:: V4L
3
4.. _dv-controls:
5
6*******************************
7Digital Video Control Reference
8*******************************
9
10The Digital Video control class is intended to control receivers and
11transmitters for `VGA <http://en.wikipedia.org/wiki/Vga>`__,
12`DVI <http://en.wikipedia.org/wiki/Digital_Visual_Interface>`__
13(Digital Visual Interface), HDMI (:ref:`hdmi`) and DisplayPort
14(:ref:`dp`). These controls are generally expected to be private to
15the receiver or transmitter subdevice that implements them, so they are
16only exposed on the ``/dev/v4l-subdev*`` device node.
17
18.. note::
19
20 Note that these devices can have multiple input or output pads which are
21 hooked up to e.g. HDMI connectors. Even though the subdevice will
22 receive or transmit video from/to only one of those pads, the other pads
23 can still be active when it comes to EDID (Extended Display
24 Identification Data, :ref:`vesaedid`) and HDCP (High-bandwidth Digital
25 Content Protection System, :ref:`hdcp`) processing, allowing the
26 device to do the fairly slow EDID/HDCP handling in advance. This allows
27 for quick switching between connectors.
28
29These pads appear in several of the controls in this section as
30bitmasks, one bit for each pad. Bit 0 corresponds to pad 0, bit 1 to pad
311, etc. The maximum value of the control is the set of valid pads.
32
33
34.. _dv-control-id:
35
36Digital Video Control IDs
37=========================
38
39``V4L2_CID_DV_CLASS (class)``
40 The Digital Video class descriptor.
41
42``V4L2_CID_DV_TX_HOTPLUG (bitmask)``
43 Many connectors have a hotplug pin which is high if EDID information
44 is available from the source. This control shows the state of the
45 hotplug pin as seen by the transmitter. Each bit corresponds to an
46 output pad on the transmitter. If an output pad does not have an
47 associated hotplug pin, then the bit for that pad will be 0. This
48 read-only control is applicable to DVI-D, HDMI and DisplayPort
49 connectors.
50
51``V4L2_CID_DV_TX_RXSENSE (bitmask)``
52 Rx Sense is the detection of pull-ups on the TMDS clock lines. This
53 normally means that the sink has left/entered standby (i.e. the
54 transmitter can sense that the receiver is ready to receive video).
55 Each bit corresponds to an output pad on the transmitter. If an
56 output pad does not have an associated Rx Sense, then the bit for
57 that pad will be 0. This read-only control is applicable to DVI-D
58 and HDMI devices.
59
60``V4L2_CID_DV_TX_EDID_PRESENT (bitmask)``
61 When the transmitter sees the hotplug signal from the receiver it
62 will attempt to read the EDID. If set, then the transmitter has read
63 at least the first block (= 128 bytes). Each bit corresponds to an
64 output pad on the transmitter. If an output pad does not support
65 EDIDs, then the bit for that pad will be 0. This read-only control
66 is applicable to VGA, DVI-A/D, HDMI and DisplayPort connectors.
67
68``V4L2_CID_DV_TX_MODE``
69 (enum)
70
71enum v4l2_dv_tx_mode -
72 HDMI transmitters can transmit in DVI-D mode (just video) or in HDMI
73 mode (video + audio + auxiliary data). This control selects which
74 mode to use: V4L2_DV_TX_MODE_DVI_D or V4L2_DV_TX_MODE_HDMI.
75 This control is applicable to HDMI connectors.
76
77``V4L2_CID_DV_TX_RGB_RANGE``
78 (enum)
79
80enum v4l2_dv_rgb_range -
81 Select the quantization range for RGB output. V4L2_DV_RANGE_AUTO
82 follows the RGB quantization range specified in the standard for the
83 video interface (ie. :ref:`cea861` for HDMI).
84 V4L2_DV_RANGE_LIMITED and V4L2_DV_RANGE_FULL override the
85 standard to be compatible with sinks that have not implemented the
86 standard correctly (unfortunately quite common for HDMI and DVI-D).
87 Full range allows all possible values to be used whereas limited
88 range sets the range to (16 << (N-8)) - (235 << (N-8)) where N is
89 the number of bits per component. This control is applicable to VGA,
90 DVI-A/D, HDMI and DisplayPort connectors.
91
92``V4L2_CID_DV_TX_IT_CONTENT_TYPE``
93 (enum)
94
95enum v4l2_dv_it_content_type -
96 Configures the IT Content Type of the transmitted video. This
97 information is sent over HDMI and DisplayPort connectors as part of
98 the AVI InfoFrame. The term 'IT Content' is used for content that
99 originates from a computer as opposed to content from a TV broadcast
100 or an analog source. The enum v4l2_dv_it_content_type defines
101 the possible content types:
102
103.. tabularcolumns:: |p{7.3cm}|p{10.2cm}|
104
105.. flat-table::
106 :header-rows: 0
107 :stub-columns: 0
108
109 * - ``V4L2_DV_IT_CONTENT_TYPE_GRAPHICS``
110 - Graphics content. Pixel data should be passed unfiltered and
111 without analog reconstruction.
112 * - ``V4L2_DV_IT_CONTENT_TYPE_PHOTO``
113 - Photo content. The content is derived from digital still pictures.
114 The content should be passed through with minimal scaling and
115 picture enhancements.
116 * - ``V4L2_DV_IT_CONTENT_TYPE_CINEMA``
117 - Cinema content.
118 * - ``V4L2_DV_IT_CONTENT_TYPE_GAME``
119 - Game content. Audio and video latency should be minimized.
120 * - ``V4L2_DV_IT_CONTENT_TYPE_NO_ITC``
121 - No IT Content information is available and the ITC bit in the AVI
122 InfoFrame is set to 0.
123
124
125
126``V4L2_CID_DV_RX_POWER_PRESENT (bitmask)``
127 Detects whether the receiver receives power from the source (e.g.
128 HDMI carries 5V on one of the pins). This is often used to power an
129 eeprom which contains EDID information, such that the source can
130 read the EDID even if the sink is in standby/power off. Each bit
131 corresponds to an input pad on the receiver. If an input pad
132 cannot detect whether power is present, then the bit for that pad
133 will be 0. This read-only control is applicable to DVI-D, HDMI and
134 DisplayPort connectors.
135
136``V4L2_CID_DV_RX_RGB_RANGE``
137 (enum)
138
139enum v4l2_dv_rgb_range -
140 Select the quantization range for RGB input. V4L2_DV_RANGE_AUTO
141 follows the RGB quantization range specified in the standard for the
142 video interface (ie. :ref:`cea861` for HDMI).
143 V4L2_DV_RANGE_LIMITED and V4L2_DV_RANGE_FULL override the
144 standard to be compatible with sources that have not implemented the
145 standard correctly (unfortunately quite common for HDMI and DVI-D).
146 Full range allows all possible values to be used whereas limited
147 range sets the range to (16 << (N-8)) - (235 << (N-8)) where N is
148 the number of bits per component. This control is applicable to VGA,
149 DVI-A/D, HDMI and DisplayPort connectors.
150
151``V4L2_CID_DV_RX_IT_CONTENT_TYPE``
152 (enum)
153
154enum v4l2_dv_it_content_type -
155 Reads the IT Content Type of the received video. This information is
156 sent over HDMI and DisplayPort connectors as part of the AVI
157 InfoFrame. The term 'IT Content' is used for content that originates
158 from a computer as opposed to content from a TV broadcast or an
159 analog source. See ``V4L2_CID_DV_TX_IT_CONTENT_TYPE`` for the
160 available content types.