Protocol drm_lease_v1

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    Copyright © 2018 NXP
    Copyright © 2019 Status Research & Development GmbH.
    Copyright © 2021 Xaver Hugl

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Interface wp_drm_lease_device_v1 — lease device

This protocol is used by Wayland compositors which act as Direct Renderering Manager (DRM) masters to lease DRM resources to Wayland clients.

The compositor will advertise one wp_drm_lease_device_v1 global for each DRM node. Some time after a client binds to the wp_drm_lease_device_v1 global, the compositor will send a drm_fd event followed by zero, one or more connector events. After all currently available connectors have been sent, the compositor will send a wp_drm_lease_device_v1.done event.

When the list of connectors available for lease changes the compositor will send wp_drm_lease_device_v1.connector events for added connectors and wp_drm_lease_connector_v1.withdrawn events for removed connectors, followed by a wp_drm_lease_device_v1.done event.

The compositor will indicate when a device is gone by removing the global via a wl_registry.global_remove event. Upon receiving this event, the client should destroy any matching wp_drm_lease_device_v1 object.

To destroy a wp_drm_lease_device_v1 object, the client must first issue a release request. Upon receiving this request, the compositor will immediately send a released event and destroy the object. The client must continue to process and discard drm_fd and connector events until it receives the released event. Upon receiving the released event, the client can safely cleanup any client-side resources.

Warning! The protocol described in this file is currently in the testing phase. Backward compatible changes may be added together with the corresponding interface version bump. Backward incompatible changes can only be done by creating a new major version of the extension.

Request wp_drm_lease_device_v1.create_lease_request — create a lease request object

Creates a lease request object.

See the documentation for wp_drm_lease_request_v1 for details.

Request wp_drm_lease_device_v1.release — release this object

Indicates the client no longer wishes to use this object. In response the compositor will immediately send the released event and destroy this object. It can however not guarantee that the client won't receive connector events before the released event. The client must not send any requests after this one, doing so will raise a wl_display error. Existing connectors, lease request and leases will not be affected.

Event wp_drm_lease_device_v1.drm_fd — open a non-master fd for this DRM node

The compositor will send this event when the wp_drm_lease_device_v1 global is bound, although there are no guarantees as to how long this takes - the compositor might need to wait until regaining DRM master. The included fd is a non-master DRM file descriptor opened for this device and the compositor must not authenticate it. The purpose of this event is to give the client the ability to query DRM and discover information which may help them pick the appropriate DRM device or select the appropriate connectors therein.

  • fd fd: DRM file descriptor

Event wp_drm_lease_device_v1.connector — advertise connectors available for leases

The compositor will use this event to advertise connectors available for lease by clients. This object may be passed into a lease request to indicate the client would like to lease that connector, see wp_drm_lease_request_v1.request_connector for details. While the compositor will make a best effort to not send disconnected connectors, no guarantees can be made.

The compositor must send the drm_fd event before sending connectors. After the drm_fd event it will send all available connectors but may send additional connectors at any time.

Event wp_drm_lease_device_v1.done — signals grouping of connectors

The compositor will send this event to indicate that it has sent all currently available connectors after the client binds to the global or when it updates the connector list, for example on hotplug, drm master change or when a leased connector becomes available again. It will similarly send this event to group wp_drm_lease_connector_v1.withdrawn events of connectors of this device.

Event wp_drm_lease_device_v1.released — the compositor has finished using the device

This event is sent in response to the release request and indicates that the compositor is done sending connector events. The compositor will destroy this object immediately after sending the event and it will become invalid. The client should release any resources associated with this device after receiving this event.

Interface wp_drm_lease_connector_v1 — a leasable DRM connector

Represents a DRM connector which is available for lease. These objects are created via wp_drm_lease_device_v1.connector events, and should be passed to lease requests via wp_drm_lease_request_v1.request_connector. Immediately after the wp_drm_lease_connector_v1 object is created the compositor will send a name, a description, a connector_id and a done event. When the description is updated the compositor will send a description event followed by a done event.

Request wp_drm_lease_connector_v1.destroy — destroy connector

The client may send this request to indicate that it will not use this connector. Clients are encouraged to send this after receiving the "withdrawn" event so that the server can release the resources associated with this connector offer. Neither existing lease requests nor leases will be affected.

Event wp_drm_lease_connector_v1.name — name

The compositor sends this event once the connector is created to indicate the name of this connector. This will not change for the duration of the Wayland session, but is not guaranteed to be consistent between sessions.

  • name string: connector name

Event wp_drm_lease_connector_v1.description — description

The compositor sends this event once the connector is created to provide a human-readable description for this connector, which may be presented to the user. The compositor may send this event multiple times over the lifetime of this object to reflect changes in the description.

  • description string: connector description

Event wp_drm_lease_connector_v1.connector_id — connector_id

The compositor sends this event once the connector is created to indicate the DRM object ID which represents the underlying connector that is being offered. Note that the final lease may include additional object IDs, such as CRTCs and planes.

  • connector_id uint: DRM connector ID

Event wp_drm_lease_connector_v1.done — all properties have been sent

This event is sent after all properties of a connector have been sent. This allows changes to the properties to be seen as atomic even if they happen via multiple events.

Event wp_drm_lease_connector_v1.withdrawn — lease offer withdrawn

Sent to indicate that the compositor will no longer honor requests for DRM leases which include this connector. The client may still issue a lease request including this connector, but the compositor will send wp_drm_lease_v1.finished without issuing a lease fd. Compositors are encouraged to send this event when they lose access to connector, for example when the connector is hot-unplugged, when the connector gets leased to a client or when the compositor loses DRM master.

Interface wp_drm_lease_request_v1 — DRM lease request

A client that wishes to lease DRM resources will attach the list of connectors advertised with wp_drm_lease_device_v1.connector that they wish to lease, then use wp_drm_lease_request_v1.submit to submit the request.

Request wp_drm_lease_request_v1.request_connector — request a connector for this lease

Indicates that the client would like to lease the given connector. This is only used as a suggestion, the compositor may choose to include any resources in the lease it issues, or change the set of leased resources at any time. Compositors are however encouraged to include the requested connector and other resources necessary to drive the connected output in the lease.

Requesting a connector that was created from a different lease device than this lease request raises the wrong_device error. Requesting a connector twice will raise the duplicate_connector error.

Request wp_drm_lease_request_v1.submit — submit the lease request

Submits the lease request and creates a new wp_drm_lease_v1 object. After calling submit the compositor will immediately destroy this object, issuing any more requests will cause a wl_diplay error. The compositor doesn't make any guarantees about the events of the lease object, clients cannot expect an immediate response. Not requesting any connectors before submitting the lease request will raise the empty_lease error.

Enum wp_drm_lease_request_v1.error

  • wrong_device: requested a connector from a different lease device
  • duplicate_connector: requested a connector twice
  • empty_lease: requested a lease without requesting a connector

Interface wp_drm_lease_v1 — a DRM lease

A DRM lease object is used to transfer the DRM file descriptor to the client and manage the lifetime of the lease.

Some time after the wp_drm_lease_v1 object is created, the compositor will reply with the lease request's result. If the lease request is granted, the compositor will send a lease_fd event. If the lease request is denied, the compositor will send a finished event without a lease_fd event.

Request wp_drm_lease_v1.destroy — destroys the lease object

The client should send this to indicate that it no longer wishes to use this lease. The compositor should use drmModeRevokeLease on the appropriate file descriptor, if necessary.

Event wp_drm_lease_v1.lease_fd — shares the DRM file descriptor

This event returns a file descriptor suitable for use with DRM-related ioctls. The client should use drmModeGetLease to enumerate the DRM objects which have been leased to them. The compositor guarantees it will not use the leased DRM objects itself until it sends the finished event. If the compositor cannot or will not grant a lease for the requested connectors, it will not send this event, instead sending the finished event.

The compositor will send this event at most once during this objects lifetime.

  • leased_fd fd: leased DRM file descriptor

Event wp_drm_lease_v1.finished — sent when the lease has been revoked

The compositor uses this event to either reject a lease request, or if it previously sent a lease_fd, to notify the client that the lease has been revoked. If the client requires a new lease, they should destroy this object and submit a new lease request. The compositor will send no further events for this object after sending the finish event. Compositors should revoke the lease when any of the leased resources become unavailable, namely when a hot-unplug occurs or when the compositor loses DRM master.