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