zircon/system/fidl/fuchsia-hardware-ramdisk/ramdisk.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.hardware.ramdisk;

using zx;

// Identifies if requests which are sent ot the ramdisk while it is
// considered "asleep" should be processed when the ramdisk wakes up.
// If this flag is not set, those requests are failed immediately.
const uint32 RAMDISK_FLAG_RESUME_ON_WAKE = 0xFF000001;

// Counters for the number of write requests since the last call to either
// "SleepAfter" or "Wake". All units are in individual blocks.
struct BlockWriteCounts {
    uint64 received;
    uint64 successful;
    uint64 failed;
};

// The interface for interacting with a instance of a ramdisk.
[Layout = "Simple"]
protocol Ramdisk {
    // Sets any of the |RAMDISK_FLAG_*| flags.
    SetFlags(uint32 flags) -> (zx.status s);

    // Wakes a ramdisk, if it was sleeping.
    //
    // Resets the block counts being stored by the ramdisk.
    Wake() -> (zx.status s);

    // Causes the ramdisk to sleep after |count| blocks are written successfully.
    // After |count| blocks are written, requests either wait for the ramdisk to
    // be awoken (if RESUME_ON_WAKE has been set), or begin failing immediately.
    //
    // Resets the block counts being stored by the ramdisk.
    SleepAfter(uint64 count) -> (zx.status s);

    // Returns the number of write requests since the last call to either
    // "SleepAfter" or "Wake".
    GetBlockCounts() -> (zx.status s, BlockWriteCounts? counts);

    // Causes the ramdisk size to grow to |required_size| in bytes.
    // If |required_size| is smaller than the current size an error will be
    // returned. |required_size| must be a multiple of |block_size|.
    Grow(uint64 new_size) -> (zx.status s);
};

// TODO(smklein): Deduplicate GUID declarations with other FIDL interfaces.

// Matches the value of ZBI_PARTITION_GUID_LEN.
const uint32 GUID_LEN = 16;

// An array of bytes interpreted as a GUID. Wrapped in a struct to
// allow optional GUIDs.
struct GUID {
    array<uint8>:GUID_LEN value;
};

const uint32 MAX_NAME_LENGTH = 32;

[Layout = "Simple"]
protocol RamdiskController {
    // Initializes a new Ramdisk instance with the provided block size and block count.
    // Takes an optional |type_guid|, which may be queried from the ramdisk instance.
    Create(uint64 block_size, uint64 block_count, GUID? type_guid) -> (zx.status s, string:MAX_NAME_LENGTH? name);

    // Initializes a new Ramdisk instance from a VMO. Uses a block size of |PAGE_SIZE|,
    // and derives the block count from the size of the VMO.
    CreateFromVmo(handle<vmo> vmo) -> (zx.status s, string:MAX_NAME_LENGTH? name);
};