Message-Id: <0464D1F0-1721-4AC2-A7E7-DACDF004F4B9@darmarit.de>
Date:   Fri, 26 Aug 2016 11:34:38 +0200
From:   Markus Heiser <markus.heiser@...marit.de>
To:     Jonathan Corbet <corbet@....net>,
        Jani Nikula <jani.nikula@...el.com>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>
Cc:     linux-doc@...r.kernel.org,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        Sebastian Reichel <sre@...nel.org>
Subject: Re: [PATCH 0/3] RFC: The beginning of a proper driver-api book


Am 23.08.2016 um 16:43 schrieb Mauro Carvalho Chehab <mchehab@...pensource.com>:

> Em Mon, 22 Aug 2016 14:57:40 -0600
> Jonathan Corbet <corbet@....net> escreveu:
> 
>> This short series convers device-drivers.tmpl into the RST format, splits
>> it up, and sets up the result under Documentation/driver-api/.  For added
>> fun, I've taken one top-level file (hsi.txt) and folded it into the
>> document as a way of showing the direction I'm thinking I would like things
>> to go.  There is plenty more of this sort of work that could be done, to
>> say the least - this is just a beginning!
>> 
>> The formatted results can be seen at:
>> 
>>   http://static.lwn.net/kerneldoc/driver-api/index.html
> 
> Thanks for doing that! IMHO, the conversion of this book is indeed
> one of the first things to be done.

>> As part of the long-term task to turn Documentation/ into less of a horror
>> movie, I'd like to collect documentation of the driver-specific API here.

Hi, 

here are my 2cent, about the *generic* content from the kernel-doc
directive:

.. kernel-doc:: kernel/sched/core.c
  :export:

IMHO directives like the one above are to *generic*. If I read this directive
I would expect, that all exported symbols are documented. But this is a false
estimation!

In my POC I use a more restrictive kernel-doc parser 
(https://github.com/return42/linuxdoc). For the directive above the parser
logs, that some of the exported symbols are not found / not documented:

$ kernel-doc --quiet --list-exports kernel/sched/core.c
[exported undocumented  ] set_cpus_allowed_ptr 
[exported undocumented  ] kick_process 
[exported function      ] wake_up_process 
[exported undocumented  ] preempt_notifier_inc 
[exported undocumented  ] preempt_notifier_dec 
[exported function      ] preempt_notifier_register 
[exported function      ] preempt_notifier_unregister 
[exported undocumented  ] single_task_running 
[exported undocumented  ] preempt_count_add 
[exported undocumented  ] preempt_count_sub 
[exported undocumented  ] schedule 
[exported undocumented  ] preempt_schedule 
[exported function      ] preempt_schedule_notrace 
[exported undocumented  ] default_wake_function 
[exported undocumented  ] set_user_nice 
[exported function      ] sched_setscheduler 
[exported undocumented  ] sched_setattr 
[exported function      ] sched_setscheduler_nocheck 
[exported undocumented  ] _cond_resched 
[exported undocumented  ] __cond_resched_lock 
[exported undocumented  ] __cond_resched_softirq 
[exported function      ] yield 
[exported function      ] yield_to 
[exported undocumented  ] io_schedule_timeout 
[exported undocumented  ] __might_sleep 
[exported undocumented  ] ___might_sleep 


The driver-api is full of *generic* content and IMHO it is not really clear 
what would be a part of the resulting documentation. To illustrate, you
can take a look on the (old) *automatic* conversion of mine at:

 http://return42.github.io/sphkerneldoc/books/device-drivers/index.html

There you see a list of 'Oops: Document generation inconsistency.' 
This kind of missing documentation grows up with changes to 
the source files while there are no errors reported.

What I mean: in most use cases it is better to be explicit and name the 
functions, structs or whatever which should be a part of the documentation.
e.g.::

 .. kernel-doc:: kernel/sched/core.c
    :functions: wake_up_process yield ...

By being explicit, the kernel-doc parser has a chance to identify requested
but missing documentation and log related error messages.

Summarized:

- *explicit* is better than implicit.
- the *generic* part of kernel-doc parser should more restrictive

These are my thoughts, even if we do nothing to handle it, we 
should aware about this.

-- Markus --
> 
>> Arguably gpu/ and the media API stuff should eventually move here, though
>> we can discuss the color of that particular shed some other day.
> 
> Yeah, let's finish converting everything to rst, and then see what would
> be the best way to organize it.
> 
> I have a split feelings with regards to media kAPI and driver-specific
> stuff if it is better to keep it at the device-drivers book, or at a
> single media book (with currently has 1031 pages on PDF output),
> but let's postpone such discussion.
> 
> I'm afraid that we'll end needing to split it more than what would be
> desired, in order to fix some issues with the PDF output 
> part/chapter/section numbering. Unfortunately, ReST markup is too poor
> to describe multi-part books, and doesn't have anything to describe
> multi-book projects.
> 
>> Meanwhile, I'd appreciate comments on the general idea.
> 
> I like the general idea of breaking device-drivers.tmpl into multiple
> files. IMHO, that will make easier to maintain it long term.
> 
> After looking on all 3 patches, they all look good, as a concept.
> 
> Yet, IMHO, there are a few things to be fixed before merging it. See
> my comments to patch 2/3.
> 
> Regards,
> Mauro
> 
>> 
>> Cc: Jani Nikula <jani.nikula@...el.com>
>> Cc: Mauro Carvalho Chehab <mchehab@...pensource.com>
>> Cc: Sebastian Reichel <sre@...nel.org>
>> 
>> Jonathan Corbet (3):
>> Docs: sphinxify device-drivers.tmpl
>> docs: split up the driver book
>> docs: Pull HSI documentation together
>> 
>> Documentation/DocBook/Makefile                 |   2 +-
>> Documentation/DocBook/device-drivers.tmpl      | 521 -------------------------
>> Documentation/driver-api/basics.rst            | 120 ++++++
>> Documentation/driver-api/frame-buffer.rst      |  62 +++
>> Documentation/driver-api/index.rst             |  24 ++
>> Documentation/driver-api/infrastructure.rst    | 169 ++++++++
>> Documentation/driver-api/input.rst             |  51 +++
>> Documentation/driver-api/message-based.rst     |  30 ++
>> Documentation/driver-api/miscellaneous.rst     |  50 +++
>> Documentation/driver-api/serial-interfaces.rst | 189 +++++++++
>> Documentation/driver-api/sound.rst             |  54 +++
>> Documentation/hsi.txt                          |  75 ----
>> Documentation/index.rst                        |   1 +
>> MAINTAINERS                                    |   2 +-
>> 14 files changed, 752 insertions(+), 598 deletions(-)
>> delete mode 100644 Documentation/DocBook/device-drivers.tmpl
>> create mode 100644 Documentation/driver-api/basics.rst
>> create mode 100644 Documentation/driver-api/frame-buffer.rst
>> create mode 100644 Documentation/driver-api/index.rst
>> create mode 100644 Documentation/driver-api/infrastructure.rst
>> create mode 100644 Documentation/driver-api/input.rst
>> create mode 100644 Documentation/driver-api/message-based.rst
>> create mode 100644 Documentation/driver-api/miscellaneous.rst
>> create mode 100644 Documentation/driver-api/serial-interfaces.rst
>> create mode 100644 Documentation/driver-api/sound.rst
>> delete mode 100644 Documentation/hsi.txt
>> 
> 
> 
> 
> Thanks,
> Mauro
> --
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