Mode Setting Helper Functions
The DRM subsystem aims for a strong separation between core code and helper libraries. Core code takes care of general setup and teardown and decoding userspace requests to kernel internal objects. Everything else is handled by a large set of helper libraries, which can be combined freely to pick and choose for each driver what fits, and avoid shared code where special behaviour is needed.
This distinction between core code and helpers is especially strong in the modesetting code, where there's a shared userspace ABI for all drivers. This is in contrast to the render side, where pretty much everything (with very few exceptions) can be considered optional helper code.
There are a few areas these helpers can grouped into:
- Helpers to implement modesetting. The important ones here are the atomic helpers. Old drivers still often use the legacy CRTC helpers. They both share the same set of common helper vtables. For really simple drivers (anything that would have been a great fit in the deprecated fbdev subsystem) there's also the simple display pipe helpers.
- There's a big pile of helpers for handling outputs. First the generic bridge helpers for handling encoder and transcoder IP blocks. Second the panel helpers for handling panel-related information and logic. Plus then a big set of helpers for the various sink standards (DisplayPort, HDMI, MIPI DSI). Finally there's also generic helpers for handling output probing, and for dealing with EDIDs.
- The last group of helpers concerns itself with the frontend side of a display pipeline: Planes, handling rectangles for visibility checking and scissoring, flip queues and assorted bits.
Modeset Helper Reference for Common Vtables
Atomic Modeset Helper Functions Reference
Overview
Implementing Asynchronous Atomic Commit
Helper Functions Reference
Atomic State Reset and Initialization
Atomic State Helper Reference
Simple KMS Helper Reference
fbdev Helper Functions Reference
format Helper Functions Reference
Framebuffer CMA Helper Functions Reference
Framebuffer GEM Helper Reference
Bridges
Overview
Bridge Operations
Bridge Connector Helper
Bridge Helper Reference
Bridge Connector Helper Reference
Panel-Bridge Helper Reference
Panel Helper Reference
Panel Self Refresh Helper Reference
HDCP Helper Functions Reference
Display Port Helper Functions Reference
Display Port CEC Helper Functions Reference
Display Port Dual Mode Adaptor Helper Functions Reference
Display Port MST Helpers
Overview
Functions Reference
Topology Lifetime Internals
These functions aren't exported to drivers, but are documented here to help make the MST topology helpers easier to understand
MIPI DBI Helper Functions Reference
MIPI DSI Helper Functions Reference
Display Stream Compression Helper Functions Reference
Output Probing Helper Functions Reference
EDID Helper Functions Reference
SCDC Helper Functions Reference
HDMI Infoframes Helper Reference
Strictly speaking this is not a DRM helper library but generally useable by any driver interfacing with HDMI outputs like v4l or alsa drivers. But it nicely fits into the overall topic of mode setting helper libraries and hence is also included here.