160 lines
6.8 KiB
ReStructuredText
160 lines
6.8 KiB
ReStructuredText
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.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
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.. _dv-controls:
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*******************************
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Digital Video Control Reference
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*******************************
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The Digital Video control class is intended to control receivers and
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transmitters for `VGA <http://en.wikipedia.org/wiki/Vga>`__,
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`DVI <http://en.wikipedia.org/wiki/Digital_Visual_Interface>`__
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(Digital Visual Interface), HDMI (:ref:`hdmi`) and DisplayPort
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(:ref:`dp`). These controls are generally expected to be private to
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the receiver or transmitter subdevice that implements them, so they are
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only exposed on the ``/dev/v4l-subdev*`` device node.
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.. note::
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Note that these devices can have multiple input or output pads which are
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hooked up to e.g. HDMI connectors. Even though the subdevice will
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receive or transmit video from/to only one of those pads, the other pads
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can still be active when it comes to EDID (Extended Display
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Identification Data, :ref:`vesaedid`) and HDCP (High-bandwidth Digital
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Content Protection System, :ref:`hdcp`) processing, allowing the
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device to do the fairly slow EDID/HDCP handling in advance. This allows
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for quick switching between connectors.
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These pads appear in several of the controls in this section as
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bitmasks, one bit for each pad. Bit 0 corresponds to pad 0, bit 1 to pad
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1, etc. The maximum value of the control is the set of valid pads.
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.. _dv-control-id:
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Digital Video Control IDs
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=========================
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``V4L2_CID_DV_CLASS (class)``
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The Digital Video class descriptor.
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``V4L2_CID_DV_TX_HOTPLUG (bitmask)``
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Many connectors have a hotplug pin which is high if EDID information
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is available from the source. This control shows the state of the
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hotplug pin as seen by the transmitter. Each bit corresponds to an
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output pad on the transmitter. If an output pad does not have an
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associated hotplug pin, then the bit for that pad will be 0. This
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read-only control is applicable to DVI-D, HDMI and DisplayPort
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connectors.
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``V4L2_CID_DV_TX_RXSENSE (bitmask)``
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Rx Sense is the detection of pull-ups on the TMDS clock lines. This
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normally means that the sink has left/entered standby (i.e. the
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transmitter can sense that the receiver is ready to receive video).
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Each bit corresponds to an output pad on the transmitter. If an
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output pad does not have an associated Rx Sense, then the bit for
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that pad will be 0. This read-only control is applicable to DVI-D
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and HDMI devices.
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``V4L2_CID_DV_TX_EDID_PRESENT (bitmask)``
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When the transmitter sees the hotplug signal from the receiver it
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will attempt to read the EDID. If set, then the transmitter has read
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at least the first block (= 128 bytes). Each bit corresponds to an
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output pad on the transmitter. If an output pad does not support
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EDIDs, then the bit for that pad will be 0. This read-only control
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is applicable to VGA, DVI-A/D, HDMI and DisplayPort connectors.
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``V4L2_CID_DV_TX_MODE``
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(enum)
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enum v4l2_dv_tx_mode -
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HDMI transmitters can transmit in DVI-D mode (just video) or in HDMI
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mode (video + audio + auxiliary data). This control selects which
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mode to use: V4L2_DV_TX_MODE_DVI_D or V4L2_DV_TX_MODE_HDMI.
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This control is applicable to HDMI connectors.
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``V4L2_CID_DV_TX_RGB_RANGE``
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(enum)
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enum v4l2_dv_rgb_range -
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Select the quantization range for RGB output. V4L2_DV_RANGE_AUTO
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follows the RGB quantization range specified in the standard for the
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video interface (ie. :ref:`cea861` for HDMI).
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V4L2_DV_RANGE_LIMITED and V4L2_DV_RANGE_FULL override the
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standard to be compatible with sinks that have not implemented the
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standard correctly (unfortunately quite common for HDMI and DVI-D).
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Full range allows all possible values to be used whereas limited
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range sets the range to (16 << (N-8)) - (235 << (N-8)) where N is
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the number of bits per component. This control is applicable to VGA,
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DVI-A/D, HDMI and DisplayPort connectors.
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``V4L2_CID_DV_TX_IT_CONTENT_TYPE``
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(enum)
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enum v4l2_dv_it_content_type -
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Configures the IT Content Type of the transmitted video. This
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information is sent over HDMI and DisplayPort connectors as part of
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the AVI InfoFrame. The term 'IT Content' is used for content that
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originates from a computer as opposed to content from a TV broadcast
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or an analog source. The enum v4l2_dv_it_content_type defines
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the possible content types:
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.. tabularcolumns:: |p{7.3cm}|p{10.2cm}|
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.. flat-table::
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:header-rows: 0
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:stub-columns: 0
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* - ``V4L2_DV_IT_CONTENT_TYPE_GRAPHICS``
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- Graphics content. Pixel data should be passed unfiltered and
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without analog reconstruction.
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* - ``V4L2_DV_IT_CONTENT_TYPE_PHOTO``
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- Photo content. The content is derived from digital still pictures.
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The content should be passed through with minimal scaling and
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picture enhancements.
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* - ``V4L2_DV_IT_CONTENT_TYPE_CINEMA``
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- Cinema content.
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* - ``V4L2_DV_IT_CONTENT_TYPE_GAME``
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- Game content. Audio and video latency should be minimized.
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* - ``V4L2_DV_IT_CONTENT_TYPE_NO_ITC``
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- No IT Content information is available and the ITC bit in the AVI
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InfoFrame is set to 0.
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``V4L2_CID_DV_RX_POWER_PRESENT (bitmask)``
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Detects whether the receiver receives power from the source (e.g.
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HDMI carries 5V on one of the pins). This is often used to power an
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eeprom which contains EDID information, such that the source can
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read the EDID even if the sink is in standby/power off. Each bit
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corresponds to an input pad on the receiver. If an input pad
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cannot detect whether power is present, then the bit for that pad
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will be 0. This read-only control is applicable to DVI-D, HDMI and
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DisplayPort connectors.
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``V4L2_CID_DV_RX_RGB_RANGE``
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(enum)
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enum v4l2_dv_rgb_range -
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Select the quantization range for RGB input. V4L2_DV_RANGE_AUTO
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follows the RGB quantization range specified in the standard for the
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video interface (ie. :ref:`cea861` for HDMI).
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V4L2_DV_RANGE_LIMITED and V4L2_DV_RANGE_FULL override the
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standard to be compatible with sources that have not implemented the
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standard correctly (unfortunately quite common for HDMI and DVI-D).
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Full range allows all possible values to be used whereas limited
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range sets the range to (16 << (N-8)) - (235 << (N-8)) where N is
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the number of bits per component. This control is applicable to VGA,
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DVI-A/D, HDMI and DisplayPort connectors.
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``V4L2_CID_DV_RX_IT_CONTENT_TYPE``
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(enum)
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enum v4l2_dv_it_content_type -
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Reads the IT Content Type of the received video. This information is
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sent over HDMI and DisplayPort connectors as part of the AVI
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InfoFrame. The term 'IT Content' is used for content that originates
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from a computer as opposed to content from a TV broadcast or an
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analog source. See ``V4L2_CID_DV_TX_IT_CONTENT_TYPE`` for the
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available content types.
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