[PATCH v3 2/4] docs: allow to pass extra CSS themes via make

[Mauro Carvalho Chehab <mchehab+huawei@kernel.org>]

Specially when the RTD theme is not used, it makes sense to
allow specifying extra CSS files via a make variable.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---

See [PATCH v3 0/4] at: https://lore.kernel.org/all/cover.1638369365.git.mchehab+huawei@kernel.org/

 Documentation/Makefile             | 8 +++++++-
 Documentation/conf.py              | 7 +++++++
 Documentation/doc-guide/sphinx.rst | 3 +++
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/Documentation/Makefile b/Documentation/Makefile
index d4039d77b32a..b3ccd1925cd3 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -20,6 +20,7 @@ SPHINXBUILD   = sphinx-build
 SPHINXOPTS    =
 SPHINXDIRS    = .
 THEME         =
+CSS           =
 _SPHINXDIRS   = $(sort $(patsubst $(srctree)/Documentation/%/index.rst,%,$(wildcard $(srctree)/Documentation/*/index.rst)))
 SPHINX_CONF   = conf.py
 PAPER         =
@@ -85,7 +86,10 @@ quiet_cmd_sphinx = SPHINX  $@ --> file://$(abspath $(BUILDDIR)/$3/$4)
 	-D version=$(KERNELVERSION) -D release=$(KERNELRELEASE) \
 	$(ALLSPHINXOPTS) \
 	$(abspath $(srctree)/$(src)/$5) \
-	$(abspath $(BUILDDIR)/$3/$4)
+	$(abspath $(BUILDDIR)/$3/$4) && \
+	if [ "x$(CSS)" != "x" ]; then \
+		cp $(CSS) $(BUILDDIR)/$3/_static/; \
+	fi
 
 htmldocs:
 	@$(srctree)/scripts/sphinx-pre-install --version-check
@@ -157,4 +161,6 @@ dochelp:
 	@echo
 	@echo '   make THEME={sphinx-theme} selects a different Sphinx theme.'
 	@echo
+	@echo '   make CSS={a .css file} adds a CSS override file for html/epub output.'
+	@echo
 	@echo  '  Default location for the generated documents is Documentation/output'
diff --git a/Documentation/conf.py b/Documentation/conf.py
index 082c3ac9dd33..0e2593e4d357 100644
--- a/Documentation/conf.py
+++ b/Documentation/conf.py
@@ -210,6 +210,7 @@ highlight_language = 'none'
 
 # Default theme
 html_theme = 'sphinx_rtd_theme'
+html_css_files = []
 
 if "THEME" in os.environ:
     html_theme = os.environ["THEME"]
@@ -229,6 +230,12 @@ if html_theme == 'sphinx_rtd_theme':
     except ImportError:
         html_theme = 'classic'
 
+if "CSS" in os.environ:
+    css = os.environ["CSS"].split(" ")
+
+    for l in css:
+        html_css_files.append(l)
+
 if major <= 1 and minor < 8:
     html_context = {
         'css_files': [],
diff --git a/Documentation/doc-guide/sphinx.rst b/Documentation/doc-guide/sphinx.rst
index 33a527f5ae64..e25bc033aad3 100644
--- a/Documentation/doc-guide/sphinx.rst
+++ b/Documentation/doc-guide/sphinx.rst
@@ -138,6 +138,9 @@ To pass extra options to Sphinx, you can use the ``SPHINXOPTS`` make
 variable. For example, use ``make SPHINXOPTS=-v htmldocs`` to get more verbose
 output.
 
+It is also possible to pass an extra CSS overlay file, in order to customize
+the html layout, by using the ``CSS`` make variable.
+
 By default, the build will try to use the Read the Docs sphinx theme:
 
     https://github.com/readthedocs/sphinx_rtd_theme
-- 
2.33.1