DRM database property: link-status

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Details

Name

link-status

Flags

<none>

Type

enum

Attached to

connector

Specification

{"Good", "Bad"}

Documentation

Connector link-status property to indicate the status of link. The
default value of link-status is "GOOD". If something fails during or
after modeset, the kernel driver may set this to "BAD" and issue a
hotplug uevent. Drivers should update this value using
drm_connector_set_link_status_property().

When user-space receives the hotplug uevent and detects a "BAD"
link-status, the sink doesn't receive pixels anymore (e.g. the screen
becomes completely black). The list of available modes may have
changed. User-space is expected to pick a new mode if the current one
has disappeared and perform a new modeset with link-status set to
"GOOD" to re-enable the connector.

If multiple connectors share the same CRTC and one of them gets a "BAD"
link-status, the other are unaffected (ie. the sinks still continue to
receive pixels).

When user-space performs an atomic commit on a connector with a "BAD"
link-status without resetting the property to "GOOD", the sink may
still not receive pixels. When user-space performs an atomic commit
which resets the link-status property to "GOOD" without the
ALLOW_MODESET flag set, it might fail because a modeset is required.

User-space can only change link-status to "GOOD", changing it to "BAD"
is a no-op.

For backwards compatibility with non-atomic userspace the kernel
tries to automatically set the link-status back to "GOOD" in the
SETCRTC IOCTL. This might fail if the mode is no longer valid, similar
to how it might fail if a different screen has been connected in the
interim.

Driver support