Enum BufferCollectionTokenGroupRequest

pub enum BufferCollectionTokenGroupRequest {
    Sync {
        responder: BufferCollectionTokenGroupSyncResponder,
    },
    Release {
        control_handle: BufferCollectionTokenGroupControlHandle,
    },
    SetName {
        payload: NodeSetNameRequest,
        control_handle: BufferCollectionTokenGroupControlHandle,
    },
    SetDebugClientInfo {
        payload: NodeSetDebugClientInfoRequest,
        control_handle: BufferCollectionTokenGroupControlHandle,
    },
    SetDebugTimeoutLogDeadline {
        payload: NodeSetDebugTimeoutLogDeadlineRequest,
        control_handle: BufferCollectionTokenGroupControlHandle,
    },
    SetVerboseLogging {
        control_handle: BufferCollectionTokenGroupControlHandle,
    },
    GetNodeRef {
        responder: BufferCollectionTokenGroupGetNodeRefResponder,
    },
    IsAlternateFor {
        payload: NodeIsAlternateForRequest,
        responder: BufferCollectionTokenGroupIsAlternateForResponder,
    },
    GetBufferCollectionId {
        responder: BufferCollectionTokenGroupGetBufferCollectionIdResponder,
    },
    SetWeak {
        control_handle: BufferCollectionTokenGroupControlHandle,
    },
    SetWeakOk {
        payload: NodeSetWeakOkRequest,
        control_handle: BufferCollectionTokenGroupControlHandle,
    },
    AttachNodeTracking {
        payload: NodeAttachNodeTrackingRequest,
        control_handle: BufferCollectionTokenGroupControlHandle,
    },
    CreateChild {
        payload: BufferCollectionTokenGroupCreateChildRequest,
        control_handle: BufferCollectionTokenGroupControlHandle,
    },
    CreateChildrenSync {
        payload: BufferCollectionTokenGroupCreateChildrenSyncRequest,
        responder: BufferCollectionTokenGroupCreateChildrenSyncResponder,
    },
    AllChildrenPresent {
        control_handle: BufferCollectionTokenGroupControlHandle,
    },
    _UnknownMethod {
        ordinal: u64,
        control_handle: BufferCollectionTokenGroupControlHandle,
        method_type: MethodType,
    },
}

The sysmem implementation is consistent with a logical / conceptual model of allocation / logical allocation as follows:

As usual, a logical allocation considers either the root and all nodes with connectivity to the root that don’t transit a [fuchsia.sysmem2/Node] created with [fuchsia.sysmem2/BufferCollection.AttachToken], or a subtree rooted at an AttachToken Node and all Node(s) with connectivity to that subtree that don’t transit another AttachToken. This is called the logical allocation pruned subtree, or pruned subtree for short.

During constraints aggregation, each [fuchsia.sysmem2/BufferCollectionTokenGroup] will select a single child Node among its direct children. The rest of the children will appear to fail the logical allocation, while the selected child may succeed.

When more than one BufferCollectionTokenGroup exists in the overall logical allocation pruned subtree, the relative priority between two groups is equivalent to their ordering in a DFS pre-order iteration of the tree, with parents higher priority than children, and left children higher priority than right children.

When a particular child of a group is selected (whether provisionally during a constraints aggregation attempt, or as a final selection), the non-selection of other children of the group will “hide” any other groups under those non-selected children.

Within a logical allocation, aggregation is attempted first by provisionally selecting child 0 of the highest-priority group, and child 0 of the next highest-priority group that isn’t hidden by the provisional selections so far, etc.

If that aggregation attempt fails, aggregation will be attempted with the ordinal 0 child of all the same groups except the lowest priority non-hidden group which will provisionally select its ordinal 1 child (and then child 2 and so on). If a new lowest-priority group is un-hidden as provisional selections are updated, that newly un-hidden lowest-priority group has all its children considered in order, before changing the provisional selection in the former lowest-priority group. In terms of result, this is equivalent to systematic enumeration of all possible combinations of choices in a counting-like order updating the lowest-priority group the most often and the highest-priority group the least often. Rather than actually attempting aggregation with all the combinations, we can skip over combinations which are redundant/equivalent due to hiding without any change to the result.

Attempted constraint aggregations of enumerated non-equivalent combinations of choices continue in this manner until either (a) all aggregation attempts fail in which case the overall logical allocation fails, or (b) until an attempted aggregation succeeds, in which case buffer allocation (if needed; if this is the pruned subtree rooted at the overall root Node) is attempted once. If buffer allocation based on the first successful constraints aggregation fails, the overall logical allocation fails (there is no buffer allocation retry / re-attempt). If buffer allocation succeeds (or is not needed due to being a pruned subtree that doesn’t include the root), the logical allocation succeeds.

If this prioritization scheme cannot reasonably work for your usage of sysmem, please don’t hesitate to contact sysmem folks to discuss potentially adding a way to achieve what you need.

Please avoid creating a large number of BufferCollectionTokenGroup(s) per logical allocation, especially with large number of children overall, and especially in cases where aggregation may reasonably be expected to often fail using ordinal 0 children and possibly with later children as well. Sysmem mitigates potentially high time complexity of evaluating too many child combinations/selections across too many groups by simply failing logical allocation beyond a certain (fairly high, but not huge) max number of considered group child combinations/selections. More advanced (and more complicated) mitigation is not anticipated to be practically necessary or worth the added complexity. Please contact sysmem folks if the max limit is getting hit or if you anticipate it getting hit, to discuss potential options.

Prefer to use multiple [fuchsia.sysmem2/ImageFormatConstraints] in a single [fuchsia.sysmem2/BufferCollectionConstraints] when feasible (when a participant just needs to express the ability to work with more than a single [fuchsia.images2/PixelFormat], with sysmem choosing which PixelFormat to use among those supported by all participants).

Similar to [fuchsia.sysmem2/BufferCollectionToken] and [fuchsia.sysmem2/BufferCollection], closure of the BufferCollectionTokenGroup channel without sending [fuchsia.sysmem2/Node.Release] first will cause buffer collection failure (or subtree failure if using [fuchsia.sysmem2/BufferCollectionToken.SetDispensable] or [fuchsia.sysmem2/BufferCollection.AttachToken] and the BufferCollectionTokenGroup is part of a subtree under such a node that doesn’t propagate failure to its parent).

Epitaphs are not used in this protocol.

Variants

Sync

Ensure that previous messages have been received server side. This is particularly useful after previous messages that created new tokens, because a token must be known to the sysmem server before sending the token to another participant.

Calling [fuchsia.sysmem2/BufferCollectionToken.Sync] on a token that isn’t/wasn’t a valid token risks the Sync stalling forever. See [fuchsia.sysmem2/Allocator.ValidateBufferCollectionToken] for one way to mitigate the possibility of a hostile/fake [fuchsia.sysmem2/BufferCollectionToken] at the cost of one round trip. Another way is to pass the token to [fuchsia.sysmem2/Allocator/BindSharedCollection], which also validates the token as part of exchanging it for a [fuchsia.sysmem2/BufferCollection] channel, and [fuchsia.sysmem2/BufferCollection.Sync] can then be used without risk of stalling.

After creating one or more fuchsia.sysmem2/BufferCollectionToken and then starting and completing a Sync, it’s then safe to send the BufferCollectionToken client ends to other participants knowing the server will recognize the tokens when they’re sent by the other participants to sysmem in a [fuchsia.sysmem2/Allocator.BindSharedCollection] message. This is an efficient way to create tokens while avoiding unnecessary round trips.

Other options include waiting for each [fuchsia.sysmem2/BufferCollectionToken.Duplicate] to complete individually (using separate call to Sync after each), or calling [fuchsia.sysmem2/BufferCollection.Sync] after a token has been converted to a BufferCollection via [fuchsia.sysmem2/Allocator.BindSharedCollection], or using [fuchsia.sysmem2/BufferCollectionToken.DuplicateSync] which includes the sync step and can create multiple tokens at once.

Fields

responder: BufferCollectionTokenGroupSyncResponder

Release

On a [fuchsia.sysmem2/BufferCollectionToken] channel:

Normally a participant will convert a BufferCollectionToken into a [fuchsia.sysmem2/BufferCollection], but a participant can instead send Release via the token (and then close the channel immediately or shortly later in response to server closing the server end), which avoids causing buffer collection failure. Without a prior Release, closing the BufferCollectionToken client end will cause buffer collection failure.

On a [fuchsia.sysmem2/BufferCollection] channel:

By default the server handles unexpected closure of a [fuchsia.sysmem2/BufferCollection] client end (without Release first) by failing the buffer collection. Partly this is to expedite closing VMO handles to reclaim memory when any participant fails. If a participant would like to cleanly close a BufferCollection without causing buffer collection failure, the participant can send Release before closing the BufferCollection client end. The Release can occur before or after SetConstraints. If before SetConstraints, the buffer collection won’t require constraints from this node in order to allocate. If after SetConstraints, the constraints are retained and aggregated, despite the lack of BufferCollection connection at the time of constraints aggregation.

On a [fuchsia.sysmem2/BufferCollectionTokenGroup] channel:

By default, unexpected closure of a BufferCollectionTokenGroup client end (without Release first) will trigger failure of the buffer collection. To close a BufferCollectionTokenGroup channel without failing the buffer collection, ensure that AllChildrenPresent() has been sent, and send Release before closing the BufferCollectionTokenGroup client end.

If Release occurs before [fuchsia.sysmem2/BufferCollectionTokenGroup.AllChildrenPresent], the buffer collection will fail (triggered by reception of Releasewithout priorAllChildrenPresent). This is intentionally not analogous to how [fuchsia.sysmem2/BufferCollection.Release] without [fuchsia.sysmem2/BufferCollection.SetConstraints] first doesn't cause buffer collection failure. For a BufferCollectionTokenGroup, clean close requires AllChildrenPresent(if not already sent), thenRelease`, then close client end.

If Release occurs after AllChildrenPresent, the children and all their constraints remain intact (just as they would if the BufferCollectionTokenGroup channel had remained open), and the client end close doesn’t trigger buffer collection failure.

On all [fuchsia.sysmem2/Node] channels (any of the above):

For brevity, the per-channel-protocol paragraphs above ignore the separate failure domain created by [fuchsia.sysmem2/BufferCollectionToken.SetDispensable] or [fuchsia.sysmem2/BufferCollection.AttachToken]. When a client end unexpectedly closes (without Release first) and that client end is under a failure domain, instead of failing the whole buffer collection, the failure domain is failed, but the buffer collection itself is isolated from failure of the failure domain. Such failure domains can be nested, in which case only the inner-most failure domain in which the Node resides fails.

Fields

control_handle: BufferCollectionTokenGroupControlHandle

SetName

Set a name for VMOs in this buffer collection.

If the name doesn’t fit in ZX_MAX_NAME_LEN, the name of the vmo itself will be truncated to fit. The name of the vmo will be suffixed with the buffer index within the collection (if the suffix fits within ZX_MAX_NAME_LEN). The name specified here (without truncation) will be listed in the inspect data.

The name only affects VMOs allocated after the name is set; this call does not rename existing VMOs. If multiple clients set different names then the larger priority value will win. Setting a new name with the same priority as a prior name doesn’t change the name.

All table fields are currently required.

• request priority The name is only set if this is the first SetName or if priority is greater than any previous priority value in prior SetName calls across all Node(s) of this buffer collection.
• request name The name for VMOs created under this buffer collection.

Fields

payload: NodeSetNameRequest

control_handle: BufferCollectionTokenGroupControlHandle

SetDebugClientInfo

Set information about the current client that can be used by sysmem to help diagnose leaking memory and allocation stalls waiting for a participant to send [fuchsia.sysmem2/BufferCollection.SetConstraints].

This sets the debug client info on this [fuchsia.sysmem2/Node] and all Node(s) derived from this Node, unless overriden by [fuchsia.sysmem2/Allocator.SetDebugClientInfo] or a later [fuchsia.sysmem2/Node.SetDebugClientInfo].

Sending [fuchsia.sysmem2/Allocator.SetDebugClientInfo] once per Allocator is the most efficient way to ensure that all fuchsia.sysmem2/Node will have at least some debug client info set, and is also more efficient than separately sending the same debug client info via [fuchsia.sysmem2/Node.SetDebugClientInfo] for each created [fuchsia.sysmem2/Node].

Also used when verbose logging is enabled (see SetVerboseLogging) to indicate which client is closing their channel first, leading to subtree failure (which can be normal if the purpose of the subtree is over, but if happening earlier than expected, the client-channel-specific name can help diagnose where the failure is first coming from, from sysmem’s point of view).

All table fields are currently required.

• request name This can be an arbitrary string, but the current process name (see fsl::GetCurrentProcessName) is a good default.
• request id This can be an arbitrary id, but the current process ID (see fsl::GetCurrentProcessKoid) is a good default.

Fields

payload: NodeSetDebugClientInfoRequest

control_handle: BufferCollectionTokenGroupControlHandle

SetDebugTimeoutLogDeadline

Sysmem logs a warning if sysmem hasn’t seen [fuchsia.sysmem2/BufferCollection.SetConstraints] from all clients within 5 seconds after creation of a new collection.

Clients can call this method to change when the log is printed. If multiple client set the deadline, it’s unspecified which deadline will take effect.

In most cases the default works well.

All table fields are currently required.

• request deadline The time at which sysmem will start trying to log the warning, unless all constraints are with sysmem by then.

Fields

payload: NodeSetDebugTimeoutLogDeadlineRequest

control_handle: BufferCollectionTokenGroupControlHandle

SetVerboseLogging

This enables verbose logging for the buffer collection.

Verbose logging includes constraints set via [fuchsia.sysmem2/BufferCollection.SetConstraints] from each client along with info set via [fuchsia.sysmem2/Node.SetDebugClientInfo] (or [fuchsia.sysmem2/Allocator.SetDebugClientInfo]) and the structure of the tree of Node(s).

Normally sysmem prints only a single line complaint when aggregation fails, with just the specific detailed reason that aggregation failed, with little surrounding context. While this is often enough to diagnose a problem if only a small change was made and everything was working before the small change, it’s often not particularly helpful for getting a new buffer collection to work for the first time. Especially with more complex trees of nodes, involving things like [fuchsia.sysmem2/BufferCollection.AttachToken], [fuchsia.sysmem2/BufferCollectionToken.SetDispensable], [fuchsia.sysmem2/BufferCollectionTokenGroup] nodes, and associated subtrees of nodes, verbose logging may help in diagnosing what the tree looks like and why it’s failing a logical allocation, or why a tree or subtree is failing sooner than expected.

The intent of the extra logging is to be acceptable from a performance point of view, under the assumption that verbose logging is only enabled on a low number of buffer collections. If we’re not tracking down a bug, we shouldn’t send this message.

Fields

control_handle: BufferCollectionTokenGroupControlHandle

GetNodeRef

This gets a handle that can be used as a parameter to [fuchsia.sysmem2/Node.IsAlternateFor] called on any [fuchsia.sysmem2/Node]. This handle is only for use as proof that the client obtained this handle from this Node.

Because this is a get not a set, no [fuchsia.sysmem2/Node.Sync] is needed between the GetNodeRef and the call to IsAlternateFor, despite the two calls typically being on different channels.

See also [fuchsia.sysmem2/Node.IsAlternateFor].

All table fields are currently required.

• response node_ref This handle can be sent via IsAlternateFor on a different Node channel, to prove that the client obtained the handle from this Node.

Fields

responder: BufferCollectionTokenGroupGetNodeRefResponder

IsAlternateFor

Check whether the calling [fuchsia.sysmem2/Node] is in a subtree rooted at a different child token of a common parent [fuchsia.sysmem2/BufferCollectionTokenGroup], in relation to the passed-in node_ref.

This call is for assisting with admission control de-duplication, and with debugging.

The node_ref must be obtained using [fuchsia.sysmem2/Node.GetNodeRef].

The node_ref can be a duplicated handle; it’s not necessary to call GetNodeRef for every call to [fuchsia.sysmem2/Node.IsAlternateFor].

If a calling token may not actually be a valid token at all due to a potentially hostile/untrusted provider of the token, call [fuchsia.sysmem2/Allocator.ValidateBufferCollectionToken] first instead of potentially getting stuck indefinitely if IsAlternateFor never responds due to a calling token not being a real token (not really talking to sysmem). Another option is to call [fuchsia.sysmem2/Allocator.BindSharedCollection] with this token first which also validates the token along with converting it to a [fuchsia.sysmem2/BufferCollection], then call IsAlternateFor.

All table fields are currently required.

• response is_alternate
  • true: The first parent node in common between the calling node and the node_ref Node is a BufferCollectionTokenGroup. This means that the calling Node and the node_ref Node will not have both their constraints apply - rather sysmem will choose one or the other of the constraints - never both. This is because only one child of a BufferCollectionTokenGroup is selected during logical allocation, with only that one child’s subtree contributing to constraints aggregation.
  • false: The first parent node in common between the calling Node and the node_ref Node is not a BufferCollectionTokenGroup. Currently, this means the first parent node in common is a BufferCollectionToken or BufferCollection (regardless of not Releaseed). This means that the calling Node and the node_ref Node may have both their constraints apply during constraints aggregation of the logical allocation, if both Node(s) are selected by any parent BufferCollectionTokenGroup(s) involved. In this case, there is no BufferCollectionTokenGroup that will directly prevent the two Node(s) from both being selected and their constraints both aggregated, but even when false, one or both Node(s) may still be eliminated from consideration if one or both Node(s) has a direct or indirect parent BufferCollectionTokenGroup which selects a child subtree other than the subtree containing the calling Node or node_ref Node.

• error [fuchsia.sysmem2/Error.NOT_FOUND] The node_ref wasn’t associated with the same buffer collection as the calling Node. Another reason for this error is if the node_ref is an [zx.Handle.EVENT] handle with sufficient rights, but isn’t actually a real node_ref obtained from GetNodeRef.
• error [fuchsia.sysmem2/Error.PROTOCOL_DEVIATION] The caller passed a node_ref that isn’t a [zx.Handle:EVENT] handle , or doesn’t have the needed rights expected on a real node_ref.
• No other failing status codes are returned by this call. However, sysmem may add additional codes in future, so the client should have sensible default handling for any failing status code.

Fields

payload: NodeIsAlternateForRequest

responder: BufferCollectionTokenGroupIsAlternateForResponder

GetBufferCollectionId

Get the buffer collection ID. This ID is also available from [fuchsia.sysmem2/Allocator.GetVmoInfo] (along with the buffer_index within the collection).

This call is mainly useful in situations where we can’t convey a [fuchsia.sysmem2/BufferCollectionToken] or [fuchsia.sysmem2/BufferCollection] directly, but can only convey a VMO handle, which can be joined back up with a BufferCollection client end that was created via a different path. Prefer to convey a BufferCollectionToken or BufferCollection directly when feasible.

Trusting a buffer_collection_id value from a source other than sysmem is analogous to trusting a koid value from a source other than zircon. Both should be avoided unless really necessary, and both require caution. In some situations it may be reasonable to refer to a pre-established BufferCollection by buffer_collection_id via a protocol for efficiency reasons, but an incoming value purporting to be a buffer_collection_id is not sufficient alone to justify granting the sender of the buffer_collection_id any capability. The sender must first prove to a receiver that the sender has/had a VMO or has/had a BufferCollectionToken to the same collection by sending a handle that sysmem confirms is a valid sysmem handle and which sysmem maps to the buffer_collection_id value. The receiver should take care to avoid assuming that a sender had a BufferCollectionToken in cases where the sender has only proven that the sender had a VMO.

• response buffer_collection_id This ID is unique per buffer collection per boot. Each buffer is uniquely identified by the buffer_collection_id and buffer_index together.

Fields

responder: BufferCollectionTokenGroupGetBufferCollectionIdResponder

SetWeak

Sets the current [fuchsia.sysmem2/Node] and all child Node(s) created after this message to weak, which means that a client’s Node client end (or a child created after this message) is not alone sufficient to keep allocated VMOs alive.

All VMOs obtained from weak Node(s) are weak sysmem VMOs. See also close_weak_asap.

This message is only permitted before the Node becomes ready for allocation (else the server closes the channel with ZX_ERR_BAD_STATE):

• BufferCollectionToken: any time
• BufferCollection: before SetConstraints
• BufferCollectionTokenGroup: before AllChildrenPresent

Currently, no conversion from strong Node to weak Node after ready for allocation is provided, but a client can simulate that by creating an additional Node before allocation and setting that additional Node to weak, and then potentially at some point later sending Release and closing the client end of the client’s strong Node, but keeping the client’s weak Node.

Zero strong Node(s) and zero strong VMO handles will result in buffer collection failure (all Node client end(s) will see ZX_CHANNEL_PEER_CLOSED and all close_weak_asap client_end(s) will see ZX_EVENTPAIR_PEER_CLOSED), but sysmem (intentionally) won’t notice this situation until all Node(s) are ready for allocation. For initial allocation to succeed, at least one strong Node is required to exist at allocation time, but after that client receives VMO handles, that client can BufferCollection.Release and close the client end without causing this type of failure.

This implies [fuchsia.sysmem2/Node.SetWeakOk] as well, but does not imply SetWeakOk with for_children_also true, which can be sent separately as appropriate.

Fields

control_handle: BufferCollectionTokenGroupControlHandle

SetWeakOk

This indicates to sysmem that the client is prepared to pay attention to close_weak_asap.

If sent, this message must be before [fuchsia.sysmem2/BufferCollection.WaitForAllBuffersAllocated].

All participants using a weak [fuchsia.sysmem2/BufferCollection] must send this message before WaitForAllBuffersAllocated, or a parent Node must have sent [fuchsia.sysmem2/Node.SetWeakOk] with for_child_nodes_also true, else the WaitForAllBuffersAllocated will trigger buffer collection failure.

This message is necessary because weak sysmem VMOs have not always been a thing, so older clients are not aware of the need to pay attention to close_weak_asap ZX_EVENTPAIR_PEER_CLOSED and close all remaining sysmem weak VMO handles asap. By having this message and requiring participants to indicate their acceptance of this aspect of the overall protocol, we avoid situations where an older client is delivered a weak VMO without any way for sysmem to get that VMO to close quickly later (and on a per-buffer basis).

A participant that doesn’t handle close_weak_asap and also doesn’t retrieve any VMO handles via WaitForAllBuffersAllocated doesn’t need to send SetWeakOk (and doesn’t need to have a parent Node send SetWeakOk with for_child_nodes_also true either). However, if that same participant has a child/delegate which does retrieve VMOs, that child/delegate will need to send SetWeakOk before WaitForAllBuffersAllocated.

• request for_child_nodes_also If present and true, this means direct child nodes of this node created after this message plus all descendants of those nodes will behave as if SetWeakOk was sent on those nodes. Any child node of this node that was created before this message is not included. This setting is “sticky” in the sense that a subsequent SetWeakOk without this bool set to true does not reset the server-side bool. If this creates a problem for a participant, a workaround is to SetWeakOk with for_child_nodes_also true on child tokens instead, as appropriate. A participant should only set for_child_nodes_also true if the participant can really promise to obey close_weak_asap both for its own weak VMO handles, and for all weak VMO handles held by participants holding the corresponding child Node(s). When for_child_nodes_also is set, descendent Node(s) which are using sysmem(1) can be weak, despite the clients of those sysmem1 Node(s) not having any direct way to SetWeakOk or any direct way to find out about close_weak_asap. This only applies to descendents of this Node which are using sysmem(1), not to this Node when converted directly from a sysmem2 token to a sysmem(1) token, which will fail allocation unless an ancestor of this Node specified for_child_nodes_also true.

Fields

payload: NodeSetWeakOkRequest

control_handle: BufferCollectionTokenGroupControlHandle

AttachNodeTracking

The server_end will be closed after this Node and any child nodes have have released their buffer counts, making those counts available for reservation by a different Node via [fuchsia.sysmem2/BufferCollection.AttachToken].

The Node buffer counts may not be released until the entire tree of Node(s) is closed or failed, because [fuchsia.sysmem2/BufferCollection.Release] followed by channel close does not immediately un-reserve the Node buffer counts. Instead, the Node buffer counts remain reserved until the orphaned node is later cleaned up.

If the Node exceeds a fairly large number of attached eventpair server ends, a log message will indicate this and the Node (and the appropriate) sub-tree will fail.

The server_end will remain open when [fuchsia.sysmem2/Allocator.BindSharedCollection] converts a [fuchsia.sysmem2/BufferCollectionToken] into a [fuchsia.sysmem2/BufferCollection].

This message can also be used with a [fuchsia.sysmem2/BufferCollectionTokenGroup].

Fields

payload: NodeAttachNodeTrackingRequest

control_handle: BufferCollectionTokenGroupControlHandle

CreateChild

Create a child [fuchsia.sysmem2/BufferCollectionToken]. Only one child (including its children) will be selected during allocation (or logical allocation).

Before passing the client end of this token to [fuchsia.sysmem2/Allocator.BindSharedCollection], completion of [fuchsia.sysmem2/Node.Sync] after [fuchsia.sysmem2/BufferCollectionTokenGroup.CreateChild] is required. Or the client can use [fuchsia.sysmem2/BufferCollectionTokenGroup.CreateChildrenSync] which essentially includes the Sync.

Sending CreateChild after AllChildrenPresent is not permitted; this will fail the group’s subtree and close the connection.

After all children have been created, send AllChildrenPresent.

• request token_request The server end of the new token channel.
• request rights_attenuation_mask If ZX_RIGHT_SAME_RIGHTS, the created token allows the holder to get the same rights to buffers as the parent token (of the group) had. When the value isn’t ZX_RIGHT_SAME_RIGHTS, the value is interpretted as a bitmask with 0 bits ensuring those rights are attentuated, so 0xFFFFFFFF is a synonym for ZX_RIGHT_SAME_RIGHTS. The value 0 is not allowed and intentionally causes subtree failure.

Fields

payload: BufferCollectionTokenGroupCreateChildRequest

control_handle: BufferCollectionTokenGroupControlHandle

CreateChildrenSync

Create 1 or more child tokens at once, synchronously. In contrast to [fuchsia.sysmem2/BufferCollectionTokenGroup.CreateChild], no [fuchsia.sysmem2/Node.Sync] is required before passing the client end of a returned token to [fuchsia.sysmem2/Allocator/BindSharedCollection].

The lower-index child tokens are higher priority (attempted sooner) than higher-index child tokens.

As per all child tokens, successful aggregation will choose exactly one child among all created children (across all children created across potentially multiple calls to [fuchsia.sysmem2/BufferCollectionTokenGroup.CreateChild] and [fuchsia.sysmem2/BufferCollectionTokenGroup.CreateChildrenSync]).

The maximum permissible total number of children per group, and total number of nodes in an overall tree (from the root) are capped to limits which are not configurable via these protocols.

Sending CreateChildrenSync after AllChildrenPresent is not permitted; this will fail the group’s subtree and close the connection.

After all children have been created, send AllChildrenPresent.

• request rights_attentuation_masks The size of the rights_attentuation_masks determines the number of created child tokens. The value ZX_RIGHT_SAME_RIGHTS doesn’t attenuate any rights. The value 0xFFFFFFFF is a synonym for ZX_RIGHT_SAME_RIGHTS. For any other value, each 0 bit in the mask attenuates that right.

• response tokens The created child tokens.

Fields

payload: BufferCollectionTokenGroupCreateChildrenSyncRequest

responder: BufferCollectionTokenGroupCreateChildrenSyncResponder

AllChildrenPresent

Indicate that no more children will be created.

After creating all children, the client should send [fuchsia.sysmem2/BufferCollectionTokenGroup.AllChildrenPresent] to inform sysmem that no more children will be created, so that sysmem can know when it’s ok to start aggregating constraints.

Sending CreateChild after AllChildrenPresent is not permitted; this will fail the group’s subtree and close the connection.

If [fuchsia.sysmem2/Node.Release] is to be sent, it should be sent after AllChildrenPresent, else failure of the group’s subtree will be triggered. This is intentionally not analogous to how Release without prior [fuchsia.sysmem2/BufferCollection.SetConstraints] doesn’t cause subtree failure.

Fields

control_handle: BufferCollectionTokenGroupControlHandle

_UnknownMethod

An interaction was received which does not match any known method.

Fields

Non-exhaustive enum variants could have additional fields added in future. Therefore, non-exhaustive enum variants cannot be constructed in external crates and cannot be matched against.

ordinal: u64

Ordinal of the method that was called.

control_handle: BufferCollectionTokenGroupControlHandle

method_type: MethodType

Implementations

impl BufferCollectionTokenGroupRequest

pub fn into_sync(self) -> Option<BufferCollectionTokenGroupSyncResponder>

pub fn into_release(self) -> Option<BufferCollectionTokenGroupControlHandle>

pub fn into_set_name( self, ) -> Option<(NodeSetNameRequest, BufferCollectionTokenGroupControlHandle)>

pub fn into_set_debug_client_info( self, ) -> Option<(NodeSetDebugClientInfoRequest, BufferCollectionTokenGroupControlHandle)>

pub fn into_set_debug_timeout_log_deadline( self, ) -> Option<(NodeSetDebugTimeoutLogDeadlineRequest, BufferCollectionTokenGroupControlHandle)>

pub fn into_set_verbose_logging( self, ) -> Option<BufferCollectionTokenGroupControlHandle>

pub fn into_get_node_ref( self, ) -> Option<BufferCollectionTokenGroupGetNodeRefResponder>

pub fn into_is_alternate_for( self, ) -> Option<(NodeIsAlternateForRequest, BufferCollectionTokenGroupIsAlternateForResponder)>

pub fn into_get_buffer_collection_id( self, ) -> Option<BufferCollectionTokenGroupGetBufferCollectionIdResponder>

pub fn into_set_weak(self) -> Option<BufferCollectionTokenGroupControlHandle>

pub fn into_set_weak_ok( self, ) -> Option<(NodeSetWeakOkRequest, BufferCollectionTokenGroupControlHandle)>

pub fn into_attach_node_tracking( self, ) -> Option<(NodeAttachNodeTrackingRequest, BufferCollectionTokenGroupControlHandle)>

pub fn into_create_child( self, ) -> Option<(BufferCollectionTokenGroupCreateChildRequest, BufferCollectionTokenGroupControlHandle)>

pub fn into_create_children_sync( self, ) -> Option<(BufferCollectionTokenGroupCreateChildrenSyncRequest, BufferCollectionTokenGroupCreateChildrenSyncResponder)>

pub fn into_all_children_present( self, ) -> Option<BufferCollectionTokenGroupControlHandle>

pub fn method_name(&self) -> &'static str

Name of the method defined in FIDL

Trait Implementations

impl Debug for BufferCollectionTokenGroupRequest

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.