sdk/fidl/fuchsia.tracing.kernel/ktrace.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.tracing.kernel;

using zx;

// TODO(fxbug.dev/30408): Allow providing a vmo of the buffer to use.

[Discoverable]
protocol Controller {
    /// Start tracing.
    Start(uint32 group_mask) -> (zx.status status);

    /// Stop tracing.
    Stop() -> (zx.status status);

    /// Rewind the trace buffer.
    Rewind() -> (zx.status status);
};

const uint32 MAX_BUF = 8192;

[Discoverable]
protocol Reader {
    /// Get the number of bytes written to the trace buffer.
    /// `size` is valid if, and only if, `status` is `ZX_OK`.
    GetBytesWritten() -> (zx.status status, uint64 size);

    /// Read `count` bytes from ktrace buffer at `offset`
    /// and return `data` read upon success
    ReadAt(uint64 count, uint64 offset) -> (zx.status status, vector<uint8>:MAX_BUF data);
};