The following terms and abbreviations are used in this codebase:
DDC: Display Data Channel, a channel for communicating with a display, including the ability to fetch EDID data. Versions 2 and later are based on I2C and are used by VGI, DVI, HDMI and DisplayPort.
DDI: This term is used in Intel's documentation and probably stands for “Digital Display Interface”. It refers to a functional unit that can send data to a display using one or more interface standards (DisplayPort, HDMI, etc.). A given DDI might or might not be wired up to a physical port.
DP (or Dp): DisplayPort
DP Aux: DisplayPort's auxiliary channel
DPLL: Display PLL (Phase-Locked Loop). In this context, the term “PLL” is shorthand for “PLL-based clock”. Each display output (such as DisplayPort or HDMI) requires a clock signal, and this clock signal is provided by a DPLL, which is a functional unit in the graphics hardware.
DPCD: DisplayPort Configuration Data. This is a set of registers exposed by a DisplayPort sink device. Each register is a byte in size. The DPCD can be read and written over the DisplayPort Aux channel using “native” read and write messages, each of which can read or write a range of bytes.
EDID: Extended Display Identification Data, a standard for data describing a display. This data is provided by a display over the DDC protocol.
MSA: Main Stream Attributes, a chunk of data sent from a DisplayPort source to a display (sink).
MST: Multi-Stream Transport, a DisplayPort mode in which two displays are driven from a single DisplayPort port.
SST: Single Stream Transport, a DisplayPort mode. This is the more ordinary mode (as opposed to MST) in which a single display is driven from one DisplayPort port.