sdk/fidl/fuchsia.sysmem2/heap.fidl

// Copyright 2019 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;

/// Sysmem Heaps can have different support for different coherency
/// domains. This table contains the support status for each coherency
/// domain of a Heap.
///
/// Each member property should correspond to a coherency domain defined
/// in the CoherencyDomain enum.
table CoherencyDomainSupport {
    1: bool cpu_supported;
    2: bool ram_supported;
    3: bool inaccessible_supported;
};

/// Memory properties for a sysmem Heap.
/// Heaps send its properties to sysmem device at registration time based
/// on which sysmem can select the correct Heap to use.
table HeapProperties {
    /// Status of support for coherency domains.
    1: CoherencyDomainSupport coherency_domain_support;
    /// Indicates whether sysmem needs to clear VMOs allocated by the Heap.
    2: bool need_clear;
};

/// Manages resources on a specific sysmem heap.
protocol Heap {
    /// Request a new memory allocation of `size` on heap.
    /// For heaps which don't permit CPU access to the buffer data, this
    /// will create a VMO with an official size, but which never has any
    /// physical pages.  For such heaps, the VMO is effectively used as
    /// an opaque buffer identifier.
    ///
    /// Heaps should defer allocation of any associated resources until
    /// CreateResource(), because the caller of AllocateVmo() may simply
    /// delete the returned VMO with no further notification to the heap.
    /// In contrast, after CreateResource(), the caller guarantees that
    /// DestroyResource() or heap channel closure will occur.
    ///
    /// The caller guarantees that CreateResource() will be called prior
    /// to the returned VMO or any associated child VMO being used.
    AllocateVmo(uint64 size) -> (zx.status s, zx.handle:VMO? vmo);

    /// Create resources and associate heap-specific resources with the
    /// passed-in VMO. Resources can be hardware specific and their
    /// lifetime don't have to be tied to `vmo`. `vmo` must be a VMO
    /// (or a direct or indirect child of a VMO) acquired through a call
    /// to AllocateVmo method above.  If the passed-in vmo is a child VMO,
    /// its size must match the size of the parent VMO created by
    /// AllocateVmo().  For heaps that permit CPU access, the passed-in
    /// VMO must not have a copy-on-write relationship with the parent
    /// VMO, but rather a pass-through relationship. Successful return
    /// status indicate that Heap has established a mapping between
    /// VMO and hardware specific resources.
    ///
    /// The returned id must be passed to DestroyResource() later when
    /// resources associated with VMO are no longer needed, unless the
    /// heap channel closes first.
    ///
    /// The heap must not own/keep a handle to VMO, or any derived child
    /// VMO, or any VMAR mapping to VMO, as any of those would keep VMO
    /// alive beyond all sysmem participant usages of the vmo; instead
    /// the heap can get the vmo's koid for the heap's mapping.
    CreateResource(zx.handle:VMO vmo, SingleBufferSettings buffer_settings)
        -> (zx.status s, uint64 id);

    /// Destroy previously created resources.
    DestroyResource(uint64 id) -> ();

    /// This event is triggered when the Heap is registered. Properties
    /// of this Heap will be sent to the sysmem device in the event.
    ///
    /// Implementations should guarantee that this event should be sent
    /// immediately when it binds to a channel, and this event should be
    /// triggered only once per Heap instance.
    // TODO(fxbug.dev/57690): Remove this event and pass in HeapProperties when
    // registering sysmem Heaps after we migrate sysmem banjo proxying
    // to FIDL.
    -> OnRegister(HeapProperties properties);
};