[PATCH v6] unstable/drm-lease: DRM lease protocol support
Sebastian Wick
sebastian at sebastianwick.net
Mon Sep 2 22:15:56 UTC 2019
On 2019-07-30 14:53, Drew DeVault wrote:
> From: Marius Vlad <marius.vlad at collabora.com>
>
> DRM leasing is a feature which allows the DRM master to "lease" a
> subset
> of its DRM resources to another DRM master via drmModeCreateLease,
> which
> returns a file descriptor for the new DRM master. We use this protocol
> to negotiate the terms of the lease and transfer this file descriptor
> to
> clients.
>
> In less DRM-specific terms: this protocol allows Wayland compositors to
> give over their GPU resources (like displays) to a Wayland client to
> exclusively control.
>
> The primary use-case for this is Virtual Reality headsets, which via
> the
> non-desktop DRM property are generally not used as desktop displays by
> Wayland compositors, and for latency reasons (among others) are most
> useful to games et al if they have direct control over the DRM
> resources
> associated with it. Basically, these are peripherals which are of no
> use
> to the compositor and may be of use to a client, but since they are
> tied
> up in DRM we need to use DRM leasing to get them into client's hands.
Talking about use-cases, I'm evaluating leasing for display calibration
and profiling which requires leasing outputs which are are part of the
desktop and also requires user interaction (keyboard, mice). Are there
any ideas on how something like that would work?
I think it would be great if it worked similar to fullscreen surfaces
but input handling depends on having a surface but leasing an output is
independent.
> Signed-off-by: Marius Vlad <marius.vlad at collabora.com>
> Signed-off-by: Drew DeVault <sir at cmpwn.com>
> ---
> When implementing this for Xwayland, we realized that we would really
> like to be able to obtain a lease with zero connectors. The kernel does
> not support this today, but adding support shouldn't be especially
> difficult. v6 changes the protocol accordingly to allow for leases with
> zero connectors, though on today's kernels this will fail vaugely with
> the finished event.
>
> Makefile.am | 1 +
> unstable/drm-lease/README | 5 +
> unstable/drm-lease/drm-lease-unstable-v1.xml | 246 +++++++++++++++++++
> 3 files changed, 252 insertions(+)
> create mode 100644 unstable/drm-lease/README
> create mode 100644 unstable/drm-lease/drm-lease-unstable-v1.xml
>
> diff --git a/Makefile.am b/Makefile.am
> index 345ae6a..d9fff89 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -4,6 +4,7 @@ unstable_protocols = \
> unstable/pointer-gestures/pointer-gestures-unstable-v1.xml \
> unstable/fullscreen-shell/fullscreen-shell-unstable-v1.xml \
> unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml \
> + unstable/drm-lease/drm-lease-unstable-v1.xml \
> unstable/text-input/text-input-unstable-v1.xml \
> unstable/text-input/text-input-unstable-v3.xml \
> unstable/input-method/input-method-unstable-v1.xml \
> diff --git a/unstable/drm-lease/README b/unstable/drm-lease/README
> new file mode 100644
> index 0000000..16f8551
> --- /dev/null
> +++ b/unstable/drm-lease/README
> @@ -0,0 +1,5 @@
> +Linux DRM lease
> +
> +Maintainers:
> +Drew DeVault <sir at cmpwn.com>
> +Marius Vlad <marius-cristian.vlad at nxp.com>
> diff --git a/unstable/drm-lease/drm-lease-unstable-v1.xml
> b/unstable/drm-lease/drm-lease-unstable-v1.xml
> new file mode 100644
> index 0000000..083d004
> --- /dev/null
> +++ b/unstable/drm-lease/drm-lease-unstable-v1.xml
> @@ -0,0 +1,246 @@
> +<?xml version="1.0" encoding="UTF-8"?>
> +<protocol name="drm_lease_unstable_v1">
> + <copyright>
> + Copyright © 2018 NXP
> + Copyright © 2019 Status Research & Development GmbH.
> +
> + Permission is hereby granted, free of charge, to any person
> obtaining a
> + copy of this software and associated documentation files (the
> "Software"),
> + to deal in the Software without restriction, including without
> limitation
> + the rights to use, copy, modify, merge, publish, distribute,
> sublicense,
> + and/or sell copies of the Software, and to permit persons to whom
> the
> + Software is furnished to do so, subject to the following
> conditions:
> +
> + The above copyright notice and this permission notice (including
> the next
> + paragraph) shall be included in all copies or substantial portions
> of the
> + Software.
> +
> + THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
> EXPRESS OR
> + IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> MERCHANTABILITY,
> + FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
> SHALL
> + THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
> OR OTHER
> + LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> ARISING
> + FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> OTHER
> + DEALINGS IN THE SOFTWARE.
> + </copyright>
> +
> + <interface name="zwp_drm_lease_manager_v1" version="1">
> + <description summary="lease manager">
> + This protocol is used by Wayland compositors which act as Direct
> + Renderering Manager (DRM) masters to lease DRM resources to
> Wayland
> + clients. Once leased, the compositor will not use the leased
> resources
> + until the lease is revoked or the client closes the file
> descriptor.
> +
> + The lease manager is used to advertise connectors which are
> available for
> + leasing, and by the client to negotiate a lease request.
> +
> + Warning! The protocol described in this file is experimental and
> + backward incompatible changes may be made. Backward compatible
> changes
> + may be added together with the corresponding interface version
> bump.
> + Backward incompatible changes are done by bumping the version
> number in
> + the protocol and interface names and resetting the interface
> version.
> + Once the protocol is to be declared stable, the 'z' prefix and
> the
> + version number in the protocol and interface names are removed
> and the
> + interface version number is reset.
> + </description>
> +
> + <enum name="error">
> + <entry name="stopped_manager" value="0"
> + summary="request sent to a manager which has been stopped"/>
> + </enum>
> +
> + <request name="create_lease_request">
> + <description summary="create a lease request object">
> + Creates a lease request object.
> +
> + See the documentation for zwp_drm_lease_request_v1 for
> details.
> + </description>
> + <arg name="id" type="new_id"
> interface="zwp_drm_lease_request_v1" />
> + </request>
> +
> + <request name="stop">
> + <description summary="stop sending events">
> + Indicates the client no longer wishes to receive connector
> events. The
> + compositor may still send connector events until it sends the
> finish
> + event, however.
> +
> + The client must not send any requests after this one.
> + </description>
> + </request>
> +
> + <event name="connector">
> + <description summary="advertise connectors available for
> leases">
> + The compositor may choose to advertise 0 or more connectors
> which may be
> + leased to clients, and will use this event to do so. This
> object may be
> + passed into a lease request to lease that connector. See
> + zwp_drm_lease_request_v1.add_connector for details.
> +
> + When this global is bound, the compositor will send all
> connectors
> + available for lease, but may send additional connectors at any
> time.
> + </description>
> + <arg name="id" type="new_id"
> interface="zwp_drm_lease_connector_v1" />
> + </event>
> +
> + <event name="finished">
> + <description summary="the compositor has finished using the
> manager">
> + This event indicates that the compositor is done sending
> connector
> + events. The compositor will destroy this object immediately
> after
> + sending this event, and it will become invalid. The client
> should
> + release any resources associated with this manager after
> receiving this
> + event.
> + </description>
> + </event>
> + </interface>
> +
> + <interface name="zwp_drm_lease_connector_v1" version="1">
> + <description summary="a leasable DRM connector">
> + Represents a DRM connector which is available for lease. These
> objects are
> + created via zwp_drm_lease_manager_v1.connector, and should be
> passed into
> + lease requests via zwp_drm_lease_request_v1.add_connector.
> + </description>
> +
> + <event name="name">
> + <description summary="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.
> +
> + If the compositor also supports zxdg_output_manager_v1 and
> this
> + connector corresponds to a zxdg_output_v1, this name will
> match the
> + name of this zxdg_output_v1 object.
> + </description>
> + <arg name="name" type="string" summary="connector name" />
> + </event>
> +
> + <event name="description">
> + <description summary="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.
> + </description>
> + <arg name="description" type="string" summary="connector
> description" />
> + </event>
> +
> + <event name="connector_id">
> + <description summary="connector_id">
> + The compositor will send this event to indicate the DRM ID
> which
> + represents the underlying connector which is being offered.
> Note that
> + the final lease may include additional object IDs, such as
> CRTCs and
> + planes.
> + </description>
> + <arg name="connector_id" type="int" summary="DRM Connector ID"
> />
> + </event>
> +
> + <event name="edid">
> + <description summary="edid">
> + The compositor may send this event once the connector is
> created to
> + provide a file descriptor which may be memory-mapped to read
> the
> + connector's EDID, to assist in selecting the correct
> connectors
> + for lease. The fd must be mapped with MAP_PRIVATE by the
> recipient.
> +
> + Note that not all displays have an EDID, and this event will
> not be
> + sent in such cases.
> + </description>
> + <arg name="edid" type="fd" summary="EDID file descriptor" />
> + <arg name="size" type="uint" summary="EDID size, in bytes"/>
> + </event>
> +
> + <event name="withdrawn">
> + <description summary="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
> + zwp_drm_lease_v1.finished without issuing a lease fd.
> + </description>
> + </event>
> +
> + <request name="destroy" type="destructor">
> + <description summary="destroy connector">
> + The client may send this request to indicate that it will not
> issue a
> + lease request for this connector. Clients are encouraged to
> send this
> + after receiving the "withdrawn" request so that the server can
> release
> + the resources associated with this connector offer.
> + </description>
> + </request>
> + </interface>
> +
> + <interface name="zwp_drm_lease_request_v1" version="1">
> + <description summary="DRM lease request">
> + A client that wishes to lease DRM resources will attach the list
> of
> + connectors advertised with zwp_drm_lease_manager_v1.connector
> that they
> + wish to lease, then use zwp_drm_lease_request_v1.submit to
> submit the
> + request.
> + </description>
> +
> + <enum name="error">
> + <entry name="submitted_lease" value="0"
> + summary="attempted to reuse a submitted lease"/>
> + </enum>
> +
> + <request name="destroy" type="destructor">
> + <description summary="destroys the lease request object">
> + Indicates that the client will no longer use this lease
> request.
> + </description>
> + </request>
> +
> + <request name="request_connector">
> + <description summary="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.
> + </description>
> + <arg name="connector" type="object"
> + interface="zwp_drm_lease_connector_v1" />
> + </request>
> +
> + <request name="submit">
> + <description summary="submit the lease request">
> + Submits the lease request and creates a new zwp_drm_lease_v1
> object.
> + After calling submit, issuing any other request than destroy
> is a
> + protocol error.
> + </description>
> + <arg name="id" type="new_id" interface="zwp_drm_lease_v1" />
> + </request>
> + </interface>
> +
> + <interface name="zwp_drm_lease_v1" version="1">
> + <description summary="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.
> + </description>
> +
> + <event name="lease_fd">
> + <description summary="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. 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 immediately.
> +
> + It is a protocol error for the compositor to send this event
> more than
> + once for a given lease.
> + </description>
> + <arg name="leased_fd" type="fd" summary="leased DRM file
> descriptor" />
> + </event>
> +
> + <event name="finished">
> + <description summary="sent when the lease has been revoked">
> + When the compositor revokes the lease, it will issue this
> event to
> + notify clients of the change. 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.
> + </description>
> + </event>
> +
> + <request name="destroy" type="destructor">
> + <description summary="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, then release this
> object.
> + </description>
> + </request>
> + </interface>
> +</protocol>
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