Merge tag 'docs-6.1' of git://git.lwn.net/linux

Pull documentation updates from Jonathan Corbet:
 "There's not a huge amount of activity in the docs tree this time
  around, but a few significant changes even so:

   - A complete rewriting of the top-level index.rst file, which mostly
     reflects itself in a redone top page in the HTML-rendered docs. The
     hope is that the new organization will be a friendlier starting
     point for both users and developers.

   - Some math-rendering improvements.

   - A coding-style.rst update on the use of BUG() and WARN()

   - A big maintainer-PHP guide update.

   - Some code-of-conduct updates

   - More Chinese translation work

  Plus the usual pile of typo fixes, corrections, and updates"

* tag 'docs-6.1' of git://git.lwn.net/linux: (66 commits)
  checkpatch: warn on usage of VM_BUG_ON() and other BUG variants
  coding-style.rst: document BUG() and WARN() rules ("do not crash the kernel")
  Documentation: devres: add missing IO helper
  Documentation: devres: update IRQ helper
  Documentation/mm: modify page_referenced to folio_referenced
  Documentation/CoC: Reflect current CoC interpretation and practices
  docs/doc-guide: Add documentation on SPHINX_IMGMATH
  docs: process/5.Posting.rst: clarify use of Reported-by: tag
  docs, kprobes: Fix the wrong location of Kprobes
  docs: add a man-pages link to the front page
  docs: put atomic*.txt and memory-barriers.txt into the core-api book
  docs: move asm-annotations.rst into core-api
  docs: remove some index.rst cruft
  docs: reconfigure the HTML left column
  docs: Rewrite the front page
  docs: promote the title of process/index.rst
  Documentation: devres: add missing SPI helper
  Documentation: devres: add missing PINCTRL helpers
  docs: hugetlbpage.rst: fix a typo of hugepage size
  docs/zh_CN: Add new translation of admin-guide/bootconfig.rst
  ...

Documentation/ABI/testing/sysfs-bus-bcma

@@ -3,7 +3,7 @@ Date:		May 2011
 KernelVersion:	3.0
 Contact:	Rafał Miłecki <zajec5@gmail.com>
 Description:
-		Each BCMA core has it's manufacturer id. See
+		Each BCMA core has its manufacturer id. See
 		include/linux/bcma/bcma.h for possible values.
 
 What:		/sys/bus/bcma/devices/.../id

Documentation/ABI/testing/sysfs-bus-fcoe

@@ -31,7 +31,7 @@ Description:	'FCoE Controller' instances on the fcoe bus.
 		1) Write interface name to ctlr_create 2) Configure the FCoE
 		Controller (ctlr_X) 3) Enable the FCoE Controller to begin
 		discovery and login. The FCoE Controller is destroyed by
-		writing it's name, i.e. ctlr_X to the ctlr_delete file.
+		writing its name, i.e. ctlr_X to the ctlr_delete file.
 
 Attributes:
 

Documentation/ABI/testing/sysfs-bus-iio-proximity

@@ -18,7 +18,7 @@ Description:
 		on the signal from which time of flight measurements are
 		taken.
 		The appropriate values to take is dependent on both the
-		sensor and it's operating environment:
+		sensor and its operating environment:
 		* as3935 (0-31 range)
 		18 = indoors (default)
 		14 = outdoors

Documentation/ABI/testing/sysfs-devices-system-cpu

@@ -296,7 +296,7 @@ Description:	Processor frequency boosting control
 
 		This switch controls the boost setting for the whole system.
 		Boosting allows the CPU and the firmware to run at a frequency
-		beyond it's nominal limit.
+		beyond its nominal limit.
 
 		More details can be found in
 		Documentation/admin-guide/pm/cpufreq.rst

Documentation/ABI/testing/sysfs-platform-chipidea-usb2

@@ -2,8 +2,8 @@ What:		/sys/bus/platform/devices/ci_hdrc.0/role
 Date:		Mar 2017
 Contact:	Peter Chen <peter.chen@nxp.com>
 Description:
-		It returns string "gadget" or "host" when read it, it indicates
-		current controller role.
+		When read, it returns string "gadget" or "host", indicating
+		the current controller role.
 
-		It will do role switch when write "gadget" or "host" to it.
+		It will do role switch when "gadget" or "host" is written to it.
 		Only controller at dual-role configuration supports writing.

Documentation/ABI/testing/sysfs-power

@@ -152,7 +152,7 @@ Description:
 		case further investigation is required to determine which
 		device is causing the problem.  Note that genuine RTC clock
 		values (such as when pm_trace has not been used), can still
-		match a device and output it's name here.
+		match a device and output its name here.
 
 What:		/sys/power/pm_async
 Date:		January 2009

Documentation/RCU/checklist.rst

@@ -486,6 +486,6 @@ over a rather long period of time, but improvements are always welcome!
 	So if you need to wait for both an RCU grace period and for
 	all pre-existing call_rcu() callbacks, you will need to execute
 	both rcu_barrier() and synchronize_rcu(), if necessary, using
-	something like workqueues to to execute them concurrently.
+	something like workqueues to execute them concurrently.
 
 	See rcubarrier.rst for more information.

Documentation/RCU/lockdep.rst

@@ -61,7 +61,7 @@ checking of rcu_dereference() primitives:
 	rcu_access_pointer(p):
 		Return the value of the pointer and omit all barriers,
 		but retain the compiler constraints that prevent duplicating
-		or coalescsing.  This is useful when when testing the
+		or coalescsing.  This is useful when testing the
 		value of the pointer itself, for example, against NULL.
 
 The rcu_dereference_check() check expression can be any boolean

Documentation/admin-guide/README.rst

@@ -262,8 +262,6 @@ Compiling the kernel
  - Make sure you have at least gcc 5.1 available.
    For more information, refer to :ref:`Documentation/process/changes.rst <changes>`.
 
-   Please note that you can still run a.out user programs with this kernel.
-
  - Do a ``make`` to create a compressed kernel image. It is also
    possible to do ``make install`` if you have lilo installed to suit the
    kernel makefiles, but you may want to check your particular lilo setup first.
@@ -332,85 +330,10 @@ Compiling the kernel
 If something goes wrong
 -----------------------
 
- - If you have problems that seem to be due to kernel bugs, please check
-   the file MAINTAINERS to see if there is a particular person associated
-   with the part of the kernel that you are having trouble with. If there
-   isn't anyone listed there, then the second best thing is to mail
-   them to me (torvalds@linux-foundation.org), and possibly to any other
-   relevant mailing-list or to the newsgroup.
+If you have problems that seem to be due to kernel bugs, please follow the
+instructions at 'Documentation/admin-guide/reporting-issues.rst'.
 
- - In all bug-reports, *please* tell what kernel you are talking about,
-   how to duplicate the problem, and what your setup is (use your common
-   sense).  If the problem is new, tell me so, and if the problem is
-   old, please try to tell me when you first noticed it.
-
- - If the bug results in a message like::
-
-     unable to handle kernel paging request at address C0000010
-     Oops: 0002
-     EIP:   0010:XXXXXXXX
-     eax: xxxxxxxx   ebx: xxxxxxxx   ecx: xxxxxxxx   edx: xxxxxxxx
-     esi: xxxxxxxx   edi: xxxxxxxx   ebp: xxxxxxxx
-     ds: xxxx  es: xxxx  fs: xxxx  gs: xxxx
-     Pid: xx, process nr: xx
-     xx xx xx xx xx xx xx xx xx xx
-
-   or similar kernel debugging information on your screen or in your
-   system log, please duplicate it *exactly*.  The dump may look
-   incomprehensible to you, but it does contain information that may
-   help debugging the problem.  The text above the dump is also
-   important: it tells something about why the kernel dumped code (in
-   the above example, it's due to a bad kernel pointer). More information
-   on making sense of the dump is in Documentation/admin-guide/bug-hunting.rst
-
- - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
-   as is, otherwise you will have to use the ``ksymoops`` program to make
-   sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
-   This utility can be downloaded from
-   https://www.kernel.org/pub/linux/utils/kernel/ksymoops/ .
-   Alternatively, you can do the dump lookup by hand:
-
- - In debugging dumps like the above, it helps enormously if you can
-   look up what the EIP value means.  The hex value as such doesn't help
-   me or anybody else very much: it will depend on your particular
-   kernel setup.  What you should do is take the hex value from the EIP
-   line (ignore the ``0010:``), and look it up in the kernel namelist to
-   see which kernel function contains the offending address.
-
-   To find out the kernel function name, you'll need to find the system
-   binary associated with the kernel that exhibited the symptom.  This is
-   the file 'linux/vmlinux'.  To extract the namelist and match it against
-   the EIP from the kernel crash, do::
-
-     nm vmlinux | sort | less
-
-   This will give you a list of kernel addresses sorted in ascending
-   order, from which it is simple to find the function that contains the
-   offending address.  Note that the address given by the kernel
-   debugging messages will not necessarily match exactly with the
-   function addresses (in fact, that is very unlikely), so you can't
-   just 'grep' the list: the list will, however, give you the starting
-   point of each kernel function, so by looking for the function that
-   has a starting address lower than the one you are searching for but
-   is followed by a function with a higher address you will find the one
-   you want.  In fact, it may be a good idea to include a bit of
-   "context" in your problem report, giving a few lines around the
-   interesting one.
-
-   If you for some reason cannot do the above (you have a pre-compiled
-   kernel image or similar), telling me as much about your setup as
-   possible will help.  Please read
-   'Documentation/admin-guide/reporting-issues.rst' for details.
-
- - Alternatively, you can use gdb on a running kernel. (read-only; i.e. you
-   cannot change values or set break points.) To do this, first compile the
-   kernel with -g; edit arch/x86/Makefile appropriately, then do a ``make
-   clean``. You'll also need to enable CONFIG_PROC_FS (via ``make config``).
-
-   After you've rebooted with the new kernel, do ``gdb vmlinux /proc/kcore``.
-   You can now use all the usual gdb commands. The command to look up the
-   point where your system crashed is ``l *0xXXXXXXXX``. (Replace the XXXes
-   with the EIP value.)
-
-   gdb'ing a non-running kernel currently fails because ``gdb`` (wrongly)
-   disregards the starting offset for which the kernel is compiled.
+Hints on understanding kernel bug reports are in
+'Documentation/admin-guide/bug-hunting.rst'. More on debugging the kernel
+with gdb is in 'Documentation/dev-tools/gdb-kernel-debugging.rst' and
+'Documentation/dev-tools/kgdb.rst'.

Documentation/admin-guide/hw-vuln/spectre.rst

@@ -613,6 +613,7 @@ kernel command line.
                 eibrs                   enhanced IBRS
                 eibrs,retpoline         enhanced IBRS + Retpolines
                 eibrs,lfence            enhanced IBRS + LFENCE
+                ibrs                    use IBRS to protect kernel
 
 		Not specifying this option is equivalent to
 		spectre_v2=auto.

Documentation/admin-guide/kdump/vmcoreinfo.rst

@@ -200,7 +200,7 @@ prb
 
 A pointer to the printk ringbuffer (struct printk_ringbuffer). This
 may be pointing to the static boot ringbuffer or the dynamically
-allocated ringbuffer, depending on when the the core dump occurred.
+allocated ringbuffer, depending on when the core dump occurred.
 Used by user-space tools to read the active kernel log buffer.
 
 printk_rb_static

Documentation/admin-guide/mm/hugetlbpage.rst

@@ -65,7 +65,7 @@ HugePages_Surp
 	may be temporarily larger than the maximum number of surplus huge
 	pages when the system is under memory pressure.
 Hugepagesize
-	is the default hugepage size (in Kb).
+	is the default hugepage size (in kB).
 Hugetlb
         is the total amount of memory (in kB), consumed by huge
         pages of all sizes.

Documentation/bpf/instruction-set.rst

@@ -133,7 +133,7 @@ code field of ``BPF_END``.
 The byte swap instructions operate on the destination register
 only and do not use a separate source register or immediate value.
 
-The 1-bit source operand field in the opcode is used to to select what byte
+The 1-bit source operand field in the opcode is used to select what byte
 order the operation convert from or to:
 
   =========  =====  =================================================

Documentation/bpf/map_cgroup_storage.rst

@@ -31,7 +31,7 @@ The map uses key of type of either ``__u64 cgroup_inode_id`` or
     };
 
 ``cgroup_inode_id`` is the inode id of the cgroup directory.
-``attach_type`` is the the program's attach type.
+``attach_type`` is the program's attach type.
 
 Linux 5.9 added support for type ``__u64 cgroup_inode_id`` as the key type.
 When this key type is used, then all attach types of the particular cgroup and
@@ -155,7 +155,7 @@ However, the BPF program can still only associate with one map of each type
 ``BPF_MAP_TYPE_CGROUP_STORAGE`` or more than one
 ``BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE``.
 
-In all versions, userspace may use the the attach parameters of cgroup and
+In all versions, userspace may use the attach parameters of cgroup and
 attach type pair in ``struct bpf_cgroup_storage_key`` as the key to the BPF map
 APIs to read or update the storage for a given attachment. For Linux 5.9
 attach type shared storages, only the first value in the struct, cgroup inode

Documentation/conf.py

@@ -15,6 +15,18 @@
 import sys
 import os
 import sphinx
+import shutil
+
+# helper
+# ------
+
+def have_command(cmd):
+    """Search ``cmd`` in the ``PATH`` environment.
+
+    If found, return True.
+    If not found, return False.
+    """
+    return shutil.which(cmd) is not None
 
 # Get Sphinx version
 major, minor, patch = sphinx.version_info[:3]
@@ -107,7 +119,32 @@ else:
 autosectionlabel_prefix_document = True
 autosectionlabel_maxdepth = 2
 
-extensions.append("sphinx.ext.imgmath")
+# Load math renderer:
+# For html builder, load imgmath only when its dependencies are met.
+# mathjax is the default math renderer since Sphinx 1.8.
+have_latex =  have_command('latex')
+have_dvipng = have_command('dvipng')
+load_imgmath = have_latex and have_dvipng
+
+# Respect SPHINX_IMGMATH (for html docs only)
+if 'SPHINX_IMGMATH' in os.environ:
+    env_sphinx_imgmath = os.environ['SPHINX_IMGMATH']
+    if 'yes' in env_sphinx_imgmath:
+        load_imgmath = True
+    elif 'no' in env_sphinx_imgmath:
+        load_imgmath = False
+    else:
+        sys.stderr.write("Unknown env SPHINX_IMGMATH=%s ignored.\n" % env_sphinx_imgmath)
+
+# Always load imgmath for Sphinx <1.8 or for epub docs
+load_imgmath = (load_imgmath or (major == 1 and minor < 8)
+                or 'epub' in sys.argv)
+
+if load_imgmath:
+    extensions.append("sphinx.ext.imgmath")
+    math_renderer = 'imgmath'
+else:
+    math_renderer = 'mathjax'
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
@@ -333,7 +370,8 @@ html_static_path = ['sphinx-static']
 html_use_smartypants = False
 
 # Custom sidebar templates, maps document names to template names.
-#html_sidebars = {}
+# Note that the RTD theme ignores this.
+html_sidebars = { '**': ['searchbox.html', 'localtoc.html', 'sourcelink.html']}
 
 # Additional templates that should be rendered to pages, maps page names to
 # template names.

Documentation/core-api/asm-annotations.rst

@@ -43,10 +43,11 @@ annotated objects like this, tools can be run on them to generate more useful
 information. In particular, on properly annotated objects, ``objtool`` can be
 run to check and fix the object if needed. Currently, ``objtool`` can report
 missing frame pointer setup/destruction in functions. It can also
-automatically generate annotations for :doc:`ORC unwinder <x86/orc-unwinder>`
+automatically generate annotations for the ORC unwinder
+(Documentation/x86/orc-unwinder.rst)
 for most code. Both of these are especially important to support reliable
-stack traces which are in turn necessary for :doc:`Kernel live patching
-<livepatch/livepatch>`.
+stack traces which are in turn necessary for kernel live patching
+(Documentation/livepatch/livepatch.rst).
 
 Caveat and Discussion
 ---------------------

Documentation/core-api/cpu_hotplug.rst

@@ -560,7 +560,7 @@ available:
   * cpuhp_state_remove_instance(state, node)
   * cpuhp_state_remove_instance_nocalls(state, node)
 
-The arguments are the same as for the the cpuhp_state_add_instance*()
+The arguments are the same as for the cpuhp_state_add_instance*()
 variants above.
 
 The functions differ in the way how the installed callbacks are treated:

Documentation/core-api/index.rst

@@ -23,6 +23,7 @@ it.
    printk-formats
    printk-index
    symbol-namespaces
+   asm-annotations
 
 Data structures and low-level utilities
 =======================================
@@ -44,6 +45,8 @@ Library functionality that is used throughout the kernel.
    this_cpu_ops
    timekeeping
    errseq
+   wrappers/atomic_t
+   wrappers/atomic_bitops
 
 Low level entry and exit
 ========================
@@ -67,6 +70,7 @@ Documentation/locking/index.rst for more related documentation.
    local_ops
    padata
    ../RCU/index
+   wrappers/memory-barriers.rst
 
 Low-level hardware management
 =============================

Documentation/core-api/irq/irq-domain.rst

@@ -71,7 +71,7 @@ variety of methods:
 Note that irq domain lookups must happen in contexts that are
 compatible with a RCU read-side critical section.
 
-The irq_create_mapping() function must be called *atleast once*
+The irq_create_mapping() function must be called *at least once*
 before any call to irq_find_mapping(), lest the descriptor will not
 be allocated.
 

Documentation/core-api/wrappers/atomic_bitops.rst

@@ -0,0 +1,18 @@
+.. SPDX-License-Identifier: GPL-2.0
+   This is a simple wrapper to bring atomic_bitops.txt into the RST world
+   until such a time as that file can be converted directly.
+
+=============
+Atomic bitops
+=============
+
+.. raw:: latex
+
+    \footnotesize
+
+.. include:: ../../atomic_bitops.txt
+   :literal:
+
+.. raw:: latex
+
+    \normalsize