Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 632 insertions, 0 deletions

diff --git a/Documentation/doc-guide/kernel-doc.rst b/Documentation/doc-guide/kernel-doc.rst
new file mode 100644
index 000000000..1c148fe8e
--- /dev/null
+++ b/Documentation/doc-guide/kernel-doc.rst
@@ -0,0 +1,632 @@
+.. title:: Kernel-doc comments
+
+===========================
+Writing kernel-doc comments
+===========================
+
+The Linux kernel source files may contain structured documentation
+comments in the kernel-doc format to describe the functions, types
+and design of the code. It is easier to keep documentation up-to-date
+when it is embedded in source files.
+
+.. note:: The kernel-doc format is deceptively similar to javadoc,
+   gtk-doc or Doxygen, yet distinctively different, for historical
+   reasons. The kernel source contains tens of thousands of kernel-doc
+   comments. Please stick to the style described here.
+
+.. note:: kernel-doc does not cover Rust code: please see
+   Documentation/rust/general-information.rst instead.
+
+The kernel-doc structure is extracted from the comments, and proper
+`Sphinx C Domain`_ function and type descriptions with anchors are
+generated from them. The descriptions are filtered for special kernel-doc
+highlights and cross-references. See below for details.
+
+.. _Sphinx C Domain: http://www.sphinx-doc.org/en/stable/domains.html
+
+Every function that is exported to loadable modules using
+``EXPORT_SYMBOL`` or ``EXPORT_SYMBOL_GPL`` should have a kernel-doc
+comment. Functions and data structures in header files which are intended
+to be used by modules should also have kernel-doc comments.
+
+It is good practice to also provide kernel-doc formatted documentation
+for functions externally visible to other kernel files (not marked
+``static``). We also recommend providing kernel-doc formatted
+documentation for private (file ``static``) routines, for consistency of
+kernel source code layout. This is lower priority and at the discretion
+of the maintainer of that kernel source file.
+
+How to format kernel-doc comments
+---------------------------------
+
+The opening comment mark ``/**`` is used for kernel-doc comments. The
+``kernel-doc`` tool will extract comments marked this way. The rest of
+the comment is formatted like a normal multi-line comment with a column
+of asterisks on the left side, closing with ``*/`` on a line by itself.
+
+The function and type kernel-doc comments should be placed just before
+the function or type being described in order to maximise the chance
+that somebody changing the code will also change the documentation. The
+overview kernel-doc comments may be placed anywhere at the top indentation
+level.
+
+Running the ``kernel-doc`` tool with increased verbosity and without actual
+output generation may be used to verify proper formatting of the
+documentation comments. For example::
+
+	tools/docs/kernel-doc -v -none drivers/foo/bar.c
+
+The documentation format of ``.c`` files is also verified by the kernel build
+when it is requested to perform extra gcc checks::
+
+	make W=n
+
+However, the above command does not verify header files. These should be checked
+separately using ``kernel-doc``.
+
+Function documentation
+----------------------
+
+The general format of a function and function-like macro kernel-doc comment is::
+
+  /**
+   * function_name() - Brief description of function.
+   * @arg1: Describe the first argument.
+   * @arg2: Describe the second argument.
+   *        One can provide multiple line descriptions
+   *        for arguments.
+   *
+   * A longer description, with more discussion of the function function_name()
+   * that might be useful to those using or modifying it. Begins with an
+   * empty comment line, and may include additional embedded empty
+   * comment lines.
+   *
+   * The longer description may have multiple paragraphs.
+   *
+   * Context: Describes whether the function can sleep, what locks it takes,
+   *          releases, or expects to be held. It can extend over multiple
+   *          lines.
+   * Return: Describe the return value of function_name.
+   *
+   * The return value description can also have multiple paragraphs, and should
+   * be placed at the end of the comment block.
+   */
+
+The brief description following the function name may span multiple lines, and
+ends with an argument description, a blank comment line, or the end of the
+comment block.
+
+Function parameters
+~~~~~~~~~~~~~~~~~~~
+
+Each function argument should be described in order, immediately following
+the short function description.  Do not leave a blank line between the
+function description and the arguments, nor between the arguments.
+
+Each ``@argument:`` description may span multiple lines.
+
+.. note::
+
+   If the ``@argument`` description has multiple lines, the continuation
+   of the description should start at the same column as the previous line::
+
+      * @argument: some long description
+      *            that continues on next lines
+
+   or::
+
+      * @argument:
+      *		some long description
+      *		that continues on next lines
+
+If a function has a variable number of arguments, its description should
+be written in kernel-doc notation as::
+
+      * @...: description
+
+Function context
+~~~~~~~~~~~~~~~~
+
+The context in which a function can be called should be described in a
+section named ``Context``. This should include whether the function
+sleeps or can be called from interrupt context, as well as what locks
+it takes, releases and expects to be held by its caller.
+
+Examples::
+
+  * Context: Any context.
+  * Context: Any context. Takes and releases the RCU lock.
+  * Context: Any context. Expects <lock> to be held by caller.
+  * Context: Process context. May sleep if @gfp flags permit.
+  * Context: Process context. Takes and releases <mutex>.
+  * Context: Softirq or process context. Takes and releases <lock>, BH-safe.
+  * Context: Interrupt context.
+
+Return values
+~~~~~~~~~~~~~
+
+The return value, if any, should be described in a dedicated section
+named ``Return`` (or ``Returns``).
+
+.. note::
+
+  #) The multi-line descriptive text you provide does *not* recognize
+     line breaks, so if you try to format some text nicely, as in::
+
+	* Return:
+	* %0 - OK
+	* %-EINVAL - invalid argument
+	* %-ENOMEM - out of memory
+
+     this will all run together and produce::
+
+	Return: 0 - OK -EINVAL - invalid argument -ENOMEM - out of memory
+
+     So, in order to produce the desired line breaks, you need to use a
+     ReST list, e. g.::
+
+      * Return:
+      * * %0		- OK to runtime suspend the device
+      * * %-EBUSY	- Device should not be runtime suspended
+
+  #) If the descriptive text you provide has lines that begin with
+     some phrase followed by a colon, each of those phrases will be taken
+     as a new section heading, which probably won't produce the desired
+     effect.
+
+Structure, union, and enumeration documentation
+-----------------------------------------------
+
+The general format of a ``struct``, ``union``, and ``enum`` kernel-doc
+comment is::
+
+  /**
+   * struct struct_name - Brief description.
+   * @member1: Description of member1.
+   * @member2: Description of member2.
+   *           One can provide multiple line descriptions
+   *           for members.
+   *
+   * Description of the structure.
+   */
+
+You can replace the ``struct`` in the above example with ``union`` or
+``enum``  to describe unions or enums. ``member`` is used to mean ``struct``
+and ``union`` member names as well as enumerations in an ``enum``.
+
+The brief description following the structure name may span multiple
+lines, and ends with a member description, a blank comment line, or the
+end of the comment block.
+
+Members
+~~~~~~~
+
+Members of structs, unions and enums should be documented the same way
+as function parameters; they immediately succeed the short description
+and may be multi-line.
+
+Inside a ``struct`` or ``union`` description, you can use the ``private:`` and
+``public:`` comment tags. Structure fields that are inside a ``private:``
+area are not listed in the generated output documentation.
+
+The ``private:`` and ``public:`` tags must begin immediately following a
+``/*`` comment marker. They may optionally include comments between the
+``:`` and the ending ``*/`` marker.
+
+When ``private:`` is used on nested structs, it propagates only to inner
+structs/unions.
+
+
+Example::
+
+  /**
+   * struct my_struct - short description
+   * @a: first member
+   * @b: second member
+   * @d: fourth member
+   *
+   * Longer description
+   */
+  struct my_struct {
+      int a;
+      int b;
+  /* private: internal use only */
+      int c;
+  /* public: the next one is public */
+      int d;
+  };
+
+Nested structs/unions
+~~~~~~~~~~~~~~~~~~~~~
+
+It is possible to document nested structs and unions, like::
+
+      /**
+       * struct nested_foobar - a struct with nested unions and structs
+       * @memb1: first member of anonymous union/anonymous struct
+       * @memb2: second member of anonymous union/anonymous struct
+       * @memb3: third member of anonymous union/anonymous struct
+       * @memb4: fourth member of anonymous union/anonymous struct
+       * @bar: non-anonymous union
+       * @bar.st1: struct st1 inside @bar
+       * @bar.st2: struct st2 inside @bar
+       * @bar.st1.memb1: first member of struct st1 on union bar
+       * @bar.st1.memb2: second member of struct st1 on union bar
+       * @bar.st2.memb1: first member of struct st2 on union bar
+       * @bar.st2.memb2: second member of struct st2 on union bar
+       */
+      struct nested_foobar {
+        /* Anonymous union/struct*/
+        union {
+          struct {
+            int memb1;
+            /* private: hides memb2 from documentation */
+            int memb2;
+          };
+          /* Everything here is public again, as private scope finished */
+          struct {
+            void *memb3;
+            int memb4;
+          };
+        };
+        union {
+          struct {
+            int memb1;
+            int memb2;
+          } st1;
+          struct {
+            void *memb1;
+            int memb2;
+          } st2;
+        } bar;
+      };
+
+.. note::
+
+   #) When documenting nested structs or unions, if the ``struct``/``union``
+      ``foo`` is named, the member ``bar`` inside it should be documented as
+      ``@foo.bar:``
+   #) When the nested ``struct``/``union`` is anonymous, the member ``bar`` in
+      it should be documented as ``@bar:``
+
+In-line member documentation comments
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The structure members may also be documented in-line within the definition.
+There are two styles, single-line comments where both the opening ``/**`` and
+closing ``*/`` are on the same line, and multi-line comments where they are each
+on a line of their own, like all other kernel-doc comments::
+
+  /**
+   * struct foo - Brief description.
+   * @foo: The Foo member.
+   */
+  struct foo {
+        int foo;
+        /**
+         * @bar: The Bar member.
+         */
+        int bar;
+        /**
+         * @baz: The Baz member.
+         *
+         * Here, the member description may contain several paragraphs.
+         */
+        int baz;
+        union {
+                /** @foobar: Single line description. */
+                int foobar;
+        };
+        /** @bar2: Description for struct @bar2 inside @foo */
+        struct {
+                /**
+                 * @bar2.barbar: Description for @barbar inside @foo.bar2
+                 */
+                int barbar;
+        } bar2;
+  };
+
+Typedef documentation
+---------------------
+
+The general format of a ``typedef`` kernel-doc comment is::
+
+  /**
+   * typedef type_name - Brief description.
+   *
+   * Description of the type.
+   */
+
+Typedefs with function prototypes can also be documented::
+
+  /**
+   * typedef type_name - Brief description.
+   * @arg1: description of arg1
+   * @arg2: description of arg2
+   *
+   * Description of the type.
+   *
+   * Context: Locking context.
+   * Returns: Meaning of the return value.
+   */
+   typedef void (*type_name)(struct v4l2_ctrl *arg1, void *arg2);
+
+Variables documentation
+-----------------------
+
+The general format of a kernel-doc variable comment is::
+
+  /**
+   * var var_name - Brief description.
+   *
+   * Description of the var_name variable.
+   */
+   extern int var_name;
+
+Object-like macro documentation
+-------------------------------
+
+Object-like macros are distinct from function-like macros. They are
+differentiated by whether the macro name is immediately followed by a
+left parenthesis ('(') for function-like macros or not followed by one
+for object-like macros.
+
+Function-like macros are handled like functions by ``tools/docs/kernel-doc``.
+They may have a parameter list. Object-like macros have do not have a
+parameter list.
+
+The general format of an object-like macro kernel-doc comment is::
+
+  /**
+   * define object_name - Brief description.
+   *
+   * Description of the object.
+   */
+
+Example::
+
+  /**
+   * define MAX_ERRNO - maximum errno value that is supported
+   *
+   * Kernel pointers have redundant information, so we can use a
+   * scheme where we can return either an error code or a normal
+   * pointer with the same return value.
+   */
+  #define MAX_ERRNO	4095
+
+Example::
+
+  /**
+   * define DRM_GEM_VRAM_PLANE_HELPER_FUNCS - \
+   *	Initializes struct drm_plane_helper_funcs for VRAM handling
+   *
+   * This macro initializes struct drm_plane_helper_funcs to use the
+   * respective helper functions.
+   */
+  #define DRM_GEM_VRAM_PLANE_HELPER_FUNCS \
+	.prepare_fb = drm_gem_vram_plane_helper_prepare_fb, \
+	.cleanup_fb = drm_gem_vram_plane_helper_cleanup_fb
+
+
+Highlights and cross-references
+-------------------------------
+
+The following special patterns are recognized in the kernel-doc comment
+descriptive text and converted to proper reStructuredText markup and `Sphinx C
+Domain`_ references.
+
+.. attention:: The below are **only** recognized within kernel-doc comments,
+	       **not** within normal reStructuredText documents.
+
+``funcname()``
+  Function reference.
+
+``@parameter``
+  Name of a function parameter. (No cross-referencing, just formatting.)
+
+``%CONST``
+  Name of a constant. (No cross-referencing, just formatting.)
+
+  Examples::
+
+    %0    %NULL    %-1    %-EFAULT    %-EINVAL    %-ENOMEM
+
+````literal````
+  A literal block that should be handled as-is. The output will use a
+  ``monospaced font``.
+
+  Useful if you need to use special characters that would otherwise have some
+  meaning either by kernel-doc script or by reStructuredText.
+
+  This is particularly useful if you need to use things like ``%ph`` inside
+  a function description.
+
+``$ENVVAR``
+  Name of an environment variable. (No cross-referencing, just formatting.)
+
+``&struct name``
+  Structure reference.
+
+``&enum name``
+  Enum reference.
+
+``&typedef name``
+  Typedef reference.
+
+``&struct_name->member`` or ``&struct_name.member``
+  ``struct`` or ``union`` member reference. The cross-reference will be to the
+  ``struct`` or ``union`` definition, not the member directly.
+
+``&name``
+  A generic type reference. Prefer using the full reference described above
+  instead. This is mostly for legacy comments.
+
+Cross-referencing from reStructuredText
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+No additional syntax is needed to cross-reference the functions and types
+defined in the kernel-doc comments from reStructuredText documents.
+Just end function names with ``()`` and write ``struct``, ``union``, ``enum``
+or ``typedef`` before types.
+For example::
+
+  See foo().
+  See struct foo.
+  See union bar.
+  See enum baz.
+  See typedef meh.
+
+However, if you want custom text in the cross-reference link, that can be done
+through the following syntax::
+
+  See :c:func:`my custom link text for function foo <foo>`.
+  See :c:type:`my custom link text for struct bar <bar>`.
+
+For further details, please refer to the `Sphinx C Domain`_ documentation.
+
+.. note::
+   Variables aren't automatically cross referenced. For those, you need to
+   explicitly add a C domain cross-reference.
+
+Overview documentation comments
+-------------------------------
+
+To facilitate having source code and comments close together, you can include
+kernel-doc documentation blocks that are free-form comments instead of being
+kernel-doc for functions, structures, unions, enums, typedefs or variables.
+This could be used for something like a theory of operation for a driver or
+library code, for example.
+
+This is done by using a ``DOC:`` section keyword with a section title.
+
+The general format of an overview or high-level documentation comment is::
+
+  /**
+   * DOC: Theory of Operation
+   *
+   * The whizbang foobar is a dilly of a gizmo. It can do whatever you
+   * want it to do, at any time. It reads your mind. Here's how it works.
+   *
+   * foo bar splat
+   *
+   * The only drawback to this gizmo is that is can sometimes damage
+   * hardware, software, or its subject(s).
+   */
+
+The title following ``DOC:`` acts as a heading within the source file, but also
+as an identifier for extracting the documentation comment. Thus, the title must
+be unique within the file.
+
+=============================
+Including kernel-doc comments
+=============================
+
+The documentation comments may be included in any of the reStructuredText
+documents using a dedicated kernel-doc Sphinx directive extension.
+
+The kernel-doc directive is of the format::
+
+  .. kernel-doc:: source
+     :option:
+
+The *source* is the path to a source file, relative to the kernel source
+tree. The following directive options are supported:
+
+export: *[source-pattern ...]*
+  Include documentation for all functions in *source* that have been exported
+  using ``EXPORT_SYMBOL`` or ``EXPORT_SYMBOL_GPL`` either in *source* or in any
+  of the files specified by *source-pattern*.
+
+  The *source-pattern* is useful when the kernel-doc comments have been placed
+  in header files, while ``EXPORT_SYMBOL`` and ``EXPORT_SYMBOL_GPL`` are next to
+  the function definitions.
+
+  Examples::
+
+    .. kernel-doc:: lib/bitmap.c
+       :export:
+
+    .. kernel-doc:: include/net/mac80211.h
+       :export: net/mac80211/*.c
+
+internal: *[source-pattern ...]*
+  Include documentation for all functions and types in *source* that have
+  **not** been exported using ``EXPORT_SYMBOL`` or ``EXPORT_SYMBOL_GPL`` either
+  in *source* or in any of the files specified by *source-pattern*.
+
+  Example::
+
+    .. kernel-doc:: drivers/gpu/drm/i915/intel_audio.c
+       :internal:
+
+identifiers: *[ function/type ...]*
+  Include documentation for each *function* and *type* in *source*.
+  If no *function* is specified, the documentation for all functions
+  and types in the *source* will be included.
+  *type* can be a ``struct``, ``union``, ``enum``, ``typedef`` or ``var``
+  identifier.
+
+  Examples::
+
+    .. kernel-doc:: lib/bitmap.c
+       :identifiers: bitmap_parselist bitmap_parselist_user
+
+    .. kernel-doc:: lib/idr.c
+       :identifiers:
+
+no-identifiers: *[ function/type ...]*
+  Exclude documentation for each *function* and *type* in *source*.
+
+  Example::
+
+    .. kernel-doc:: lib/bitmap.c
+       :no-identifiers: bitmap_parselist
+
+functions: *[ function/type ...]*
+  This is an alias of the 'identifiers' directive and deprecated.
+
+doc: *title*
+  Include documentation for the ``DOC:`` paragraph identified by *title* in
+  *source*. Spaces are allowed in *title*; do not quote the *title*. The *title*
+  is only used as an identifier for the paragraph, and is not included in the
+  output. Please make sure to have an appropriate heading in the enclosing
+  reStructuredText document.
+
+  Example::
+
+    .. kernel-doc:: drivers/gpu/drm/i915/intel_audio.c
+       :doc: High Definition Audio over HDMI and Display Port
+
+Without options, the kernel-doc directive includes all documentation comments
+from the source file.
+
+The kernel-doc extension is included in the kernel source tree, at
+``Documentation/sphinx/kerneldoc.py``. Internally, it uses the
+``tools/docs/kernel-doc`` script to extract the documentation comments from
+the source.
+
+.. _kernel_doc:
+
+How to use kernel-doc to generate man pages
+-------------------------------------------
+
+To generate man pages for all files that contain kernel-doc markups, run::
+
+  $ make mandocs
+
+Or calling ``script-build-wrapper`` directly::
+
+  $ ./tools/docs/sphinx-build-wrapper mandocs
+
+The output will be at ``/man`` directory inside the output directory
+(by default: ``Documentation/output``).
+
+Optionally, it is possible to generate a partial set of man pages by
+using SPHINXDIRS:
+
+  $ make SPHINXDIRS=driver-api/media mandocs
+
+.. note::
+
+   When SPHINXDIRS={subdir} is used, it will only generate man pages for
+   the files explicitly inside a ``Documentation/{subdir}/.../*.rst`` file.