sdk/fidl/fuchsia.sysmem2/allocator.fidl

// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
library fuchsia.sysmem2;

using zx;

/// Allocates system memory buffers.
///
/// Epitaphs are not used in this protocol.
@available(added=19)
@discoverable
open protocol Allocator {
    /// Allocates a buffer collection on behalf of a single client (aka
    /// initiator) who is also the only participant (from the point of view of
    /// sysmem).
    ///
    /// This call exists mainly for temp/testing purposes.  This call skips the
    /// [`fuchsia.sysmem2/BufferCollectionToken`] stage, so there's no way to
    /// allow another participant to specify its constraints.
    ///
    /// Real clients are encouraged to use
    /// [`fuchsia.sysmem2/Allocator.AllocateSharedCollection`] instead, and to
    /// let relevant participants directly convey their own constraints to
    /// sysmem by sending `BufferCollectionToken`s to those participants.
    ///
    /// + request `collection_request` The server end of the
    ///   [`fuchsia.sysmem2/BufferCollection`].
    flexible AllocateNonSharedCollection(resource table {
        1: collection_request server_end:BufferCollection;
    });

    /// Creates a root [`fuchsia.sysmem2/BufferCollectionToken`].
    ///
    /// The `BufferCollectionToken` can be "duplicated" for distribution to
    /// participants by using
    /// [`fuchsia.sysmem2/BufferCollectionToken.Duplicate`]. Each
    /// `BufferCollectionToken` can be converted into a
    /// [`fuchsia.sysmem2.BufferCollection`] using
    /// [`fuchsia.sysmem2/Allocator.BindSharedCollection`].
    ///
    /// Buffer constraints can be set via
    /// [`fuchsia.sysmem2/BufferCollection.SetConstraints`].
    ///
    /// Success/failure to populate the buffer collection with buffers can be
    /// determined from
    /// [`fuchsia.sysmem2/BufferCollection.WaitForAllBuffersAllocated`].
    ///
    /// Closing the client end of a `BufferCollectionToken` or
    /// `BufferCollection` (without `Release` first) will fail all client ends
    /// in the same failure domain, which by default is all client ends of the
    /// buffer collection. See
    /// [`fuchsia.sysmem2/BufferCollection.SetDispensable`] and
    /// [`fuchsia.sysmem2/BufferCollection.AttachToken`] for ways to create
    /// separate failure domains within a buffer collection.
    flexible AllocateSharedCollection(resource table {
        1: token_request server_end:BufferCollectionToken;
    });

    /// Convert a [`fuchsia.sysmem2/BufferCollectionToken`] into a
    /// [`fuchsia.sysmem2/BufferCollection`].
    ///
    /// At the time of sending this message, the buffer collection hasn't yet
    /// been populated with buffers - the participant must first also send
    /// [`fuchsia.sysmem2/BufferCollection.SetConstraints`] via the
    /// `BufferCollection` client end.
    ///
    /// All `BufferCollectionToken`(s) duplicated from a root
    /// `BufferCollectionToken` (created via `AllocateSharedCollection`) must be
    /// "turned in" via `BindSharedCollection` (or `Release`ed), and all
    /// existing `BufferCollection` client ends must have sent `SetConstraints`
    /// before the logical BufferCollection will be populated with buffers (or
    /// will fail if the overall set of constraints can't be satisfied).
    ///
    /// + request `token` The client endpoint of a channel whose server end was
    ///   sent to sysmem using
    ///   [`fuchsia.sysmem2/Allocator.AllocateSharedCollection`] or whose server
    ///   end was sent to sysmem using
    ///   [`fuchsia.sysmem2/BufferCollectionToken.Duplicate`].  The token is
    ///   being "turned in" in exchange for a
    ///   [`fuchsia.sysmem2/BufferCollection`].
    /// + request `buffer_collection_request` The server end of a
    ///   [`fuchsia.sysmem2/BufferCollection`] channel.  The sender retains the
    ///   client end. The `BufferCollection` channel is a single participant's
    ///   connection to the logical buffer collection. Typically there will be
    ///   other participants with their own `BufferCollection` channel to the
    ///   logical buffer collection.
    flexible BindSharedCollection(resource table {
        1: token client_end:BufferCollectionToken;
        2: buffer_collection_request server_end:BufferCollection;
    });

    /// Checks whether a [`fuchsia.sysmem2/BufferCollectionToken`] is known to
    /// the sysmem server.
    ///
    /// With this call, the client can determine whether an incoming token is a
    /// real sysmem token that is known to the sysmem server, without any risk
    /// of getting stuck waiting forever on a potentially fake token to complete
    /// [`fuchsia.sysmem2/BufferCollectionToken.DuplicateSync`] or
    /// [`fuchsia.sysmem2/BufferCollectionToken.Sync`] (or any other two-way
    /// FIDL message). In cases where the client trusts the source of the token
    /// to provide a real token, this call is not typically needed outside of
    /// debugging.
    ///
    /// If the validate fails sometimes but succeeds other times, the source of
    /// the token may itself not be calling
    /// [`fuchsia.sysmem2/BufferCollectionToken.Sync`] or
    /// [`fuchsia.sysmem2/BufferCollection.Sync`] after creating/duplicating the
    /// token but before sending the token to the current client. It may be more
    /// convenient for the source to use
    /// [`fuchsia.sysmem2/BufferCollectionToken.DuplicateSync`] to duplicate
    /// token(s), since that call has the sync step built in. Or, the buffer
    /// collection may be failing before this call is processed by the sysmem
    /// server, as buffer collection failure cleans up sysmem's tracking of
    /// associated tokens.
    ///
    /// This call has no effect on any token.
    ///
    /// + request `token_server_koid` The koid of the server end of a channel
    ///   that might be a BufferCollectionToken channel.  This can be obtained
    ///   via `zx_object_get_info` `ZX_INFO_HANDLE_BASIC` `related_koid`.
    /// - response `is_known` true means sysmem knew of the token at the time
    ///   sysmem processed the request, but doesn't guarantee that the token is
    ///   still valid by the time the client receives the reply. What it does
    ///   guarantee is that the token at least was a real token, so a two-way
    ///   call to the token won't stall forever (will fail or succeed fairly
    ///   quickly, not stall). This can already be known implicitly if the
    ///   source of the token can be trusted to provide a real token. A false
    ///   value means the token wasn't known to sysmem at the time sysmem
    ///   processed this call, but the token may have previously been valid, or
    ///   may yet become valid. Or if the sender of the token isn't trusted to
    ///   provide a real token, the token may be fake. It's the responsibility
    ///   of the sender to sync with sysmem to ensure that previously
    ///   created/duplicated token(s) are known to sysmem, before sending the
    ///   token(s) to other participants.
    flexible ValidateBufferCollectionToken(table {
        1: token_server_koid zx.Koid;
    }) -> (table {
        1: is_known bool;
    });

    /// 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 all [`fuchsia.sysmem2/Node`](s)
    /// subsequently created by this this [`fuchsia.sysmem2/Allocator`]
    /// including any [`fuchsia.sysmem2/BufferCollection`](s) created via
    /// [`fuchsia.sysmem2/Allocator.BindSharedCollection`] (in the absence of
    /// any prior call to [`fuchsia.sysmem2/Allocator.SetDebugClientInfo`],
    /// these `BufferCollection`(s) have the same initial debug client info as
    /// the token turned in to create the `BufferCollection`).
    ///
    /// This info can be subsequently overridden on a per-`Node` basis by
    /// sending [`fuchsia.sysmem2/Node.SetDebugClientInfo`].
    ///
    /// Sending [`fuchsia.sysmem2/Allocator.SetDebugClientInfo`] once per
    /// `Allocator` is the most efficient way to ensure that all
    /// [`fuchsia.sysmem2/Node`](s) 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`].
    ///
    /// + 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.
    flexible SetDebugClientInfo(table {
        1: name string:MAX_CLIENT_NAME_LENGTH;
        2: id uint64;
    });

    /// Given a handle to a sysmem-provided VMO, this returns additional info
    /// about the corresponding sysmem logical buffer.
    ///
    /// Most callers will duplicate a VMO handle first and send the duplicate to
    /// this call.
    ///
    /// If the client has created a child VMO of a sysmem-provided VMO, that
    /// child VMO isn't considered a "sysmem VMO" for purposes of this call.
    ///
    /// + request `vmo` A handle to a sysmem-provided VMO (or see errors).
    /// - response `buffer_collection_id` The buffer collection ID, which is
    ///   unique per logical buffer collection per boot.
    /// - response `buffer_index` The buffer index of the buffer within the
    ///   buffer collection. This is the same as the index of the buffer within
    ///   [`fuchsia.sysmem2/BufferCollectionInfo.buffers`]. The `buffer_index`
    ///   is the same for all sysmem-delivered VMOs corresponding to the same
    ///   logical buffer, even if the VMO koids differ. The `buffer_index` is
    ///   only unique across buffers of a buffer collection. For a given buffer,
    ///   the combination of `buffer_collection_id` and `buffer_index` is unique
    ///   per boot.
    /// - response `close_weak_asap` Iff `vmo` is a handle to a weak sysmem VMO,
    ///   the `close_weak_asap` field will be set in the response. This handle
    ///   will signal `ZX_EVENTPAIR_PEER_CLOSED` when all weak VMO handles to
    ///   the buffer should be closed as soon as possible. This is signalled
    ///   shortly after all strong sysmem VMOs to the buffer are closed
    ///   (including any held indirectly via strong `BufferCollectionToken` or
    ///   strong `BufferCollection`). Failure to close all weak sysmem VMO
    ///   handles to the buffer quickly upon `ZX_EVENTPAIR_PEER_CLOSED` is
    ///   considered a VMO leak caused by the client still holding a weak sysmem
    ///   VMO handle and results in loud complaints to the log by sysmem. The
    ///   buffers of a collection can be freed independently of each other. The
    ///   `ZX_EVENTPAIR_PEER_CLOSED` may already be signalled before the
    ///   response arrives at the client. A client that isn't prepared to handle
    ///   weak sysmem VMOs, on seeing this field set, can close all handles to
    ///   the buffer and fail any associated request.
    /// * error `[fuchsia.sysmem2/Error.NOT_FOUND]` - the vmo isn't a sysmem
    ///   VMO. Both strong and weak sysmem VMOs can be passed to this call, and
    ///   the VMO handle passed in to this call itself keeps the VMO's info
    ///   alive for purposes of responding to this call. Because of this,
    ///   ZX_ERR_NOT_FOUND errors are unambiguous (even if there are no other
    ///   handles to the VMO when calling; even if other handles are closed
    ///   before the GetVmoInfo response arrives at the client).
    /// * error `[fuchsia.sysmem2/Error.HANDLE_ACCESS_DENIED]` The vmo isn't
    ///   capable of being used with GetVmoInfo due to rights/capability
    ///   attenuation. The VMO needs to be usable with [`zx_vmo_get_info`] with
    ///   topic [`ZX_INFO_HANDLE_BASIC`].
    /// * error `[fuchsia.sysmem2/Error.UNSPECIFIED]` The request failed for an
    ///   unspecified reason. See the log for more info.
    /// * error `[fuchsia.sysmem2/Error.PROTOCOL_DEVIATION]` The vmo field
    ///   wasn't set, or there was some other problem with the request field(s).
    flexible GetVmoInfo(resource table {
        /// `vmo` is required to be set; ownership is transferred to the server
        /// so in most cases a client will duplicate a handle and transfer the
        /// duplicate via this field.
        1: vmo zx.Handle:VMO;
    }) -> (resource table {
        1: buffer_collection_id uint64;
        2: buffer_index uint64;
        3: close_weak_asap zx.Handle:EVENTPAIR;
    }) error Error;
};