zircon/vdso/debug.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 zx;

@transport("Syscall")
closed protocol Debug {
    /// ## Summary
    ///
    /// Read a message from the debug serial port.
    ///
    /// ## Declaration
    ///
    /// ```c
    /// #include <zircon/syscalls.h>
    ///
    /// zx_status_t zx_debug_read(zx_handle_t handle,
    ///                           char* buffer,
    ///                           size_t buffer_size,
    ///                           size_t* actual);
    /// ```
    ///
    /// ## Description
    ///
    /// `zx_debug_read()` attempts to read data from the debug serial port.
    /// The parameter *buffer_size* is used to specify the byte size of the read buffer.
    /// The length of *buffer*, in bytes, is stored in the location pointed to by
    /// *actual*.
    ///
    /// This function will wait until at least one byte is available before it returns.
    /// This can return up to *buffer_size* bytes.
    ///
    /// **NOTE:** There is only one buffer of the data that is coming from the debug
    /// serial, and calling `zx_debug_read` consumes this data. If multiple programs are calling
    /// this at once, they will each receive pieces of the data stream.
    ///
    /// To use the `zx_debug_read()` function, you must specify
    /// `kernel.enable-serial-syscalls=true` on the kernel command line. Otherwise,
    /// the function returns **ZX_ERR_NOT_SUPPORTED**.
    ///
    /// ## Rights
    ///
    /// *handle* must have resource kind **ZX_RSRC_KIND_SYSTEM** with base
    /// **ZX_RSRC_SYSTEM_DEBUG_BASE**.
    ///
    /// ## Return value
    ///
    /// Returns **ZX_OK** on success. The location pointed to by *buffer* contains
    /// *actual* bytes that were read.
    ///
    /// ## Errors
    ///
    /// **ZX_ERR_NOT_SUPPORTED**  `kernel.enable-serial-syscalls` is not set to `true`
    /// on the kernel command line.
    ///
    /// **ZX_ERR_INVALID_ARGS**  *buffer* or *actual* are NULL.
    ///
    /// ## See also
    ///
    ///  - [kernel command line]
    ///  - [`zx_debug_write()`]
    ///  - [`zx_debuglog_read()`]
    ///  - [`zx_debuglog_write()`]
    ///
    /// [kernel command line]: /docs/reference/kernel/kernel_cmdline.md
    /// [`zx_debug_write()`]: debug_write.md
    /// [`zx_debuglog_read()`]: debuglog_read.md
    /// [`zx_debuglog_write()`]: debuglog_write.md
    strict Read(resource struct {
        handle Handle:RESOURCE;
    }) -> (struct {
        buffer vector<uchar>:MAX;
        actual usize64;
    }) error Status;

    /// ## Summary
    ///
    /// Write a message to the debug serial port.
    ///
    /// ## Declaration
    ///
    /// ```c
    /// #include <zircon/syscalls.h>
    ///
    /// zx_status_t zx_debug_write(const char* buffer, size_t buffer_size);
    /// ```
    ///
    /// ## Description
    ///
    /// `zx_debug_write()` attempts to write data of *buffer_size* bytes to the debug serial port.
    ///
    /// To use the `zx_debug_write()` function, you must specify
    /// `kernel.enable-serial-syscalls=true` or
    /// `kernel.enable-serial-syscalls=output-only` on the kernel command line.
    /// Otherwise, the function returns **ZX_ERR_NOT_SUPPORTED**.
    ///
    /// `zx_debug_write` is intended for diagnostic use.  Data may be dropped or
    /// truncated, but the data from two different `zx_debug_write` calls will not be
    /// interleaved or reordered.
    ///
    /// ## Rights
    ///
    /// None.
    ///
    /// ## Return value
    ///
    /// Returns **ZX_OK** on success.
    ///
    /// ## Errors
    ///
    /// **ZX_ERR_NOT_SUPPORTED**  `kernel.enable-serial-syscalls` is not set to `true`
    /// or `output-only` on the kernel command line.
    ///
    /// **ZX_ERR_INVALID_ARGS** *buffer* is NULL.
    ///
    /// ## See also
    ///
    ///  - [kernel command line]
    ///  - [`zx_debug_read()`]
    ///  - [`zx_debuglog_read()`]
    ///  - [`zx_debuglog_write()`]
    ///
    /// [kernel command line]: /docs/reference/kernel/kernel_cmdline.md
    /// [`zx_debug_read()`]: debug_read.md
    /// [`zx_debuglog_read()`]: debuglog_read.md
    /// [`zx_debuglog_write()`]: debuglog_write.md
    strict Write(struct {
        buffer vector<uchar>:MAX;
    }) -> () error Status;

    /// ## Summary
    ///
    /// TODO(fxbug.dev/32938)
    ///
    /// ## Declaration
    ///
    /// ```c
    /// #include <zircon/syscalls.h>
    ///
    /// zx_status_t zx_debug_send_command(zx_handle_t resource,
    ///                                   const char* buffer,
    ///                                   size_t buffer_size);
    /// ```
    ///
    /// ## Description
    ///
    /// To use the `zx_debug_send_command()` function, you must specify
    /// `kernel.enable-debugging-syscalls=true` on the kernel command line. Otherwise,
    /// the function returns **ZX_ERR_NOT_SUPPORTED**.
    ///
    /// TODO(fxbug.dev/32938)
    ///
    /// ## Rights
    ///
    /// *resource* must have resource kind **ZX_RSRC_KIND_SYSTEM** with base
    /// **ZX_RSRC_SYSTEM_DEBUG_BASE**.
    ///
    /// ## Return value
    ///
    /// TODO(fxbug.dev/32938)
    ///
    /// ## Errors
    ///
    /// TODO(fxbug.dev/32938)
    ///
    /// ## See also
    ///
    /// TODO(fxbug.dev/32938)
    strict SendCommand(resource struct {
        resource Handle:RESOURCE;
        buffer vector<uchar>:MAX;
    }) -> () error Status;
};