abi2doc 1.3

attribute documentation
-----------------------

`abi2doc` is a helper tool for generating and formatting sysfs attribute
documentation which is location under ``Documentation/ABI``\ in the
kernel source code.

From a `rough estimate`_, there are around 2000 attributes that are
undocumented in the kernel.

.. raw:: html

<div>
<a href="https://plot.ly/~aishpant/1/?share_key=8mG4JmyySLLYjbjTg7Uy62" target="_blank" title="sysfs line plot" style="display: block; text-align: center;"><img src="https://plot.ly/~aishpant/1.png?share_key=8mG4JmyySLLYjbjTg7Uy62" alt="sysfs line plot" style="max-width: 100%;width: 600px;" width="600" onerror="this.onerror=null;this.src='https://plot.ly/404.png';" /></a>
</div>


The ABI documentation format looks like the following:

| What: (the full sysfs path of the attribute)
| Date: (date of creation)
| KernelVersion: (kernel version it first showed up in)
| Contact: (primary contact)
| Description: (long description on usage)

`abi2doc` can fill in the '`Date`' and the '`KernelVersion`' fields with
high accuracy. The '`Contact`' details is prompted for once, and the
others '`What`' and '`Description`' are prompted on every attribute.

It also tries to collect description from various sources-

- From the commit message that introduced the attribute

- From comments around the attribute show/store functions or the attribute declaring macro.

- From the structure fields that map to the attribute.

For eg. consider the attribute declaring macro `PORT_RO(dest_id)` and its show function `port_destid_show(...)`.

.. code:: c

static ssize_t
port_destid_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct rio_mport *mport = to_rio_mport(dev);

if (mport)
return sprintf(buf, "0x%04x\n", mport->host_deviceid);
else
return -ENODEV;
}



The show functions typically contain a conversion to a driver private struct and then one or many fields from it are put in the buffer.

In the example above, the driver private structure is a struct of type `rio_mport` and the attribute `port_id` maps to the field `host_deviceid` in the structure.

.. code:: c

struct rio_mport {
...
int host_deviceid; /* Host device ID */
struct rio_ops *ops; /* low-level architecture-dependent routines */
unsigned char id; /* port ID, unique among all ports */
...
};

There's a comment against `host_deviceid` here and this can be extracted.

All sysfs attribute declaring macros are located in ``abi2doc/macros.txt``. Each
row of `macros.txt` contains an attribute declaring macro space
separated by the location of the attribute name in the macro -
`DEVICE_ATTR 0`. This list is not complete. Please send a pull request if
you find any that are not in the list.

Usage
-----

Prerequisites:

- Coccinelle - `install instructions`_
- Python 3
- Linux Kernel source code

`abi2doc` is available on `PYPI`_. Install with ``pip``:

``pip install abi2doc``

The library is currently tested against Python versions `3.4+`.

.. code:: bash

usage: abi2doc [-h] -f SOURCE_FILE -o OUTPUT_FILE

Helper for documenting Linux Kernel sysfs attributes

required arguments:
-f SOURCE_FILE linux source file to document
-o OUTPUT_FILE location of the generated sysfs ABI documentation

optional arguments:
-h, --help show this help message and exit

Example usage:

.. code:: bash

abi2doc -f drivers/video/backlight/lp855x_bl.c -o sysfs_doc.txt

The script will fill in the '`Date`' and the '`KernelVersion`' fields for
found attributes. The '`Contact`' details is prompted for once, and the
others 'What' and '`Description`' are prompted on every attribute. The
entered description will be followed by hints, as shown in a generated
file below.

::

What: /sys/class/backlight/<backlight>/bled_mode
Date: Oct, 2012
KernelVersion: 3.7
Contact: dri-devel@lists.freedesktop.org
Description:
(WO) Write to the backlight mapping mode. The backlight current
can be mapped for either exponential (value "0") or linear
mapping modes (default).
--------------------------------
%%%%% Hints below %%%%%
bled_mode DEVICE_ATTR drivers/video/backlight/lm3639_bl.c 220
--------------------------------
%%%%% store fn comments %%%%%
/* backlight mapping mode */
--------------------------------
%%%%% commit message %%%%%
commit 0f59858d511960caefb42c4535dc73c2c5f3136c
Author: G.Shark Jeong <gshark.jeong@gmail.com>
Date: Thu Oct 4 17:12:55 2012 -0700

backlight: add new lm3639 backlight driver

This driver is a general version for LM3639 backlgiht + flash driver chip
of TI.

LM3639:
The LM3639 is a single chip LCD Display Backlight driver + white LED
Camera driver. Programming is done over an I2C compatible interface.
www.ti.com

[akpm@linux-foundation.org: code layout tweaks]
Signed-off-by: G.Shark Jeong <gshark.jeong@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Daniel Jeong <daniel.jeong@ti.com>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Expected time for the scripts to run =

`(num of attrs x avg 4 min per attr)/num of cores`.

Contributions
-------------

Thank you for reading up till here. Contributions are welcome, whether
it is in the form of code or documentation. This projects consists of
scripts written in Python 3 and `Coccinelle`_.


Some top of the mind tasks are:

- [ ] spatch runs assuming 4 cores. This should be corrected to match
the developer's machine
- [ ] support for verbose & quiet mode. Some print statements are for
debugging purpose and they should be printed in verbose mode only.
- [x] utilise all cores. The ``git log -L`` command in doc.py takes a
*very* long time to run. The script would be much faster if it runs
in parallel.
- [ ] code cleanup. Some for-loops can be replaced by list
comprehensions etc. `flake8` can be useful for finding such issues.

.. _install instructions: http://coccinelle.lip6.fr/download.php
.. _PYPI: https://pypi.org/project/abi2doc/
.. _Coccinelle: http://coccinelle.lip6.fr/
.. _rough estimate: https://github.com/aishpant/documentation-scripts/blob/master/result/output.csv