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
  ...

1 files changed, 40 insertions, 2 deletions

diff --git a/Documentation/conf.py b/Documentation/conf.py
index 255384d094bf..b50c85083149 100644
--- a/Documentation/conf.py
+++ b/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.