[PATCH v4 17/18] Documentation: tracing/remotes: Add detailed tracefs layout

[Vincent Donnefort <vdonnefort@google.com>]

Add a description for each tracefs file available in a trace remote
instance.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>

diff --git a/Documentation/trace/remotes.rst b/Documentation/trace/remotes.rst
index 1f9d764f69aa..b02ebed4a03f 100644
--- a/Documentation/trace/remotes.rst
+++ b/Documentation/trace/remotes.rst
@@ -19,8 +19,8 @@ for which the host kernel can see and expose to user space.
 
 Register a remote
 =================
-A remote must provide a set of callbacks `struct trace_remote_callbacks` whom
-description can be found below. Those callbacks allows Tracefs to enable and
+A remote must provide a set of callbacks `struct trace_remote_callbacks` whose
+description can be found below. Those callbacks allow Tracefs to enable and
 disable tracing and events, to load and unload a tracing buffer (a set of
 ring-buffers) and to swap a reader page with the head page, which enables
 consuming reading.
@@ -28,8 +28,66 @@ consuming reading.
 .. kernel-doc:: include/linux/trace_remote.h
 
 Once registered, an instance will appear for this remote in the Tracefs
-directory **remotes/**. Buffers can then be read using the usual Tracefs files
-**trace_pipe** and **trace**.
+directory **remotes/**. The files within this directory allow configuring
+and reading the remote buffer (see `The File System` below).
+
+The File System
+===============
+A remote tracing instance is represented by a directory in Tracefs under
+**remotes/**. The layout and files within it are very similar to standard ftrace
+instances. Inside the remote directory, the following files and directories are
+available:
+
+  tracing_on
+	This file allows enabling or disabling the remote tracing.
+
+  buffer_size_kb
+	This file displays and allows changing the size of the per-CPU ring
+	buffers used by the remote. It also shows if the buffer is **loaded** or
+	**unloaded**. To change the size, the remote buffers must be unloaded
+	first. Remote buffers are automatically unloaded when **tracing_on** is
+	off, no one is reading the buffer (either by accessing **trace_pipe** or
+	when **dmesg** is on) and no events remain in the buffer.
+
+  trace
+	Display the human-readable content of the remote buffers. Reading this
+	file is non-consuming. Writing to this file clears the ring buffers.
+
+  trace_pipe
+	Similar to **trace** but reading it consumes the events from the ring
+	buffers (consuming read). It blocks if there are no new events.
+
+  dmesg
+	When enabled, all events from the remote are redirected to the kernel
+	dmesg. This is similar to the **tp_printk** option for in-kernel events.
+	It counts as a reader of the remote buffers and prevents unloading.
+
+  dump_on_panic
+	When enabled, the remote tracing buffer is dumped to the console when a
+	kernel panic occurs.
+
+  poll_ms
+	Modifies the polling interval for the trace_remote.
+
+  per_cpu/
+	This directory contains subdirectories for each possible CPU (e.g.,
+	**cpu0/**, **cpu1/** ...)
+
+  per_cpu/cpuX/trace
+	This is similar to the **trace** file, but it will only display the data
+	specific for the CPU. If written to, it only clears the specific CPU
+	buffer.
+
+  per_cpu/cpuX/trace_pipe
+	This is similar to the **trace_pipe** file, and is a consuming read, but
+	it will only display (and consume) the data specific to the CPU.
+
+  events/
+	This directory contains remote events that can be enabled or disabled.
+
+  events/enable
+	Allows enabling or disabling all the remote events.
+
 
 Declare a remote event
 ======================
-- 
2.55.0.571.g244d577d93-goog