The ABI documentation looks a little bit better if it starts
with the contents of the README is placed at the beginning.

Move it to the beginning of the ABI chapter. While here, improve
the README text and change the title that will be shown at the
html/pdf output to be coherent with both ABI file contents and
with the generated documentation output.

Suggested-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/20250211055809.1898623-1-mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

The undefined logic is complex and has lots of magic on it.

Implement it, using the same algorithm we have at get_abi.pl. Yet,
some tweaks to optimize performance and to make the code simpler
were added here:
- at the perl version, the tree graph had loops, so we had to
  use BFS to traverse it. On this version, the graph is a tree,
  so, it simplifies the what group for sysfs aliases;
- the logic which splits regular expressions into subgroups
  was re-written to make it faster;
- it may optionally use multiple processes to search for symbol
  matches;
- it has some additional debug levels.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/1529c255845d117696d5af57d8dc05554663afdf.1739182025.git.mchehab+huawei@kernel.org

Despite being introduced on Python 3.6, the original implementation
was too limited: it doesn't accept anything but the argument.

Even on python 3.10.12, support was still limited, as more complex
operations cause SyntaxError:

	Exception occurred:
	  File ".../linux/Documentation/sphinx/kernel_abi.py", line 48, in <module>
	    from get_abi import AbiParser
	  File ".../linux/scripts/lib/abi/abi_parser.py", line 525
	    msg += f"{part}\n{"-" * len(part)}\n\n"
                       ^
	SyntaxError: f-string: expecting '}'

Replace f-strings by normal string concatenation when it doesn't
work on Python 3.6.

Reported-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/41d2f85df134a46db46fed73a0f9697a3d2ae9ba.1739182025.git.mchehab+huawei@kernel.org

This makes them look better when generating cross-references.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/e44574cb2796861d6acbce839068ed3ef385d16c.1739182025.git.mchehab+huawei@kernel.org

Now that all ABI files are handled together, we can add a feature
at automarkup for it to generate cross-references for ABI symbols.

The cross-reference logic can produce references for all existing
files, except for README (as this is not parsed).

For symbols, they need to be an exact match of what it is
described at the docs, which is not always true due to wildcards.

If symbols at /sys /proc and /config are identical, a cross-reference
will be used.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/0b97a51b68b1c20127ad4a6a55658557fe0848d0.1739182025.git.mchehab+huawei@kernel.org

Right now, the logic parses ABI files on 4 steps, one for each
directory. While this is fine in principle, by doing that, not
all symbol cross-references will be created.

Change the logic to do the parsing only once in order to get
a global dictionary to be used when creating ABI cross-references.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/5205c53838b6ea25f4cdd4cc1e3d17c0141e75a6.1739182025.git.mchehab+huawei@kernel.org

The Documentation/ABI/README file is currently outside the
documentation tree. Yet, it may still provide some useful
information. Add it to the documentation parsing.

As a plus, this avoids a warning when detecting missing
cross-references.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/f1285dedfe4d0eb0f0af34f6a68bee6fde36dd7d.1739182025.git.mchehab+huawei@kernel.org

This way, Sphinx ABI extension can parse symbols only once, while
keep displaying results in separate files.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/41e108e816e46434aa596e5c0d25d227cb9f0fe5.1739182025.git.mchehab+huawei@kernel.org

Instead of producing a big message with all ABI contents and then
parse as a whole, simplify the code by handling each ABI symbol
in separate. As an additional benefit, there's no need to place
file/line nubers inlined at the data and use a regex to convert
them.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/15be22955e3c6df49d7256c8fd24f62b397ad0ff.1739182025.git.mchehab+huawei@kernel.org

Instead of running get_abi.py script, import AbiParser class and
handle messages directly there using an interactor. This shold save some
memory, as there's no need to exec python inside the Sphinx python
extension.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/8dbc244dcda97112c1b694e2512a5d600e62873b.1739182025.git.mchehab+huawei@kernel.org