system/fidl/fuchsia-i2c/i2c.fidl

// Copyright 2018 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.i2c;

using zx;

const uint32 MAX_TRANSFER_SIZE = 8196;  // More than enough for I2C

enum SegmentType {
    /// Flags the end of a serialized list of segments.
    END = 1;
    /// Segment to be read from the I2C device.
    READ = 2;
    /// Segment to be written to the I2C device.
    WRITE = 3;
};

/// Segment header for a serialized SlaveTransfer.
/// TODO(ZX-3029): Avoid requiring serialization and have SlaveTransfer take an argument of
/// vector<Segment>:MAX_SEGMENTS instead once we have better support in the C bindings or for C++.
struct Segment {
    uint32 type;
    uint32 len;
};

[Layout = "Simple"]
interface Device {
    /// Send and receive data on the I2C device.
    1: SlaveTransfer(vector<uint8>:MAX_TRANSFER_SIZE in) -> (zx.status s,
       vector<uint8>:MAX_TRANSFER_SIZE out);
};