linux-kernel - Re: [PATCH v3 0/4] Add SWIG Bindings to libcpupower

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Message-ID: <428a42ef-2a3b-41ec-b1a0-7886d52d621f@linuxfoundation.org>
Date: Thu, 5 Sep 2024 19:03:02 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: "John B. Wyatt IV" <jwyatt@...hat.com>
Cc: linux-pm@...r.kernel.org, Thomas Renninger <trenn@...e.com>,
 Shuah Khan <shuah@...nel.org>, "Rafael J. Wysocki" <rafael@...nel.org>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 linux-kernel@...r.kernel.org, John Kacur <jkacur@...hat.com>,
 Tomas Glozar <tglozar@...hat.com>, Arnaldo Melo <acme@...hat.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "John B. Wyatt IV" <sageofredondo@...il.com>,
 Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v3 0/4] Add SWIG Bindings to libcpupower

On 9/4/24 20:19, John B. Wyatt IV wrote:
> SWIG is a tool packaged in Fedora and other distros that can generate
> bindings from C and C++ code for several languages including Python,
> Perl, and Go. Providing bindings for scripting languages is a common feature
> to make use of libraries more accessible to more users and programs. My team
> specifically wants to expand the features of rteval. rteval is a Python program
> used to measure real time performance. We wanted to test the effect of enabling
> some levels of idle-stat to see how it affects latency, and didn't want to
> reinvent the wheel. Since SWIG requires the .o files created by libcpupower at
> compilation it makes sense to include this in the cpupower directory so that
> others can make use of them.
> 
> The V3 of this patchset includes:
> * renaming header messages as requested and adding people to Cc as
> requested
> * moving the stub (dummy) commit to the front of the patchset
> * small punctuation fixes
> 
> The V2 of this patchset includes:
> * the full definition of libcpupower headers that is needed for the bindings
> * dummy implementation in C of a function listed in the header of libcpupower
> (requested by Shuah Khan)
> * test_raw_pylibcpupower.py demonstrates an example of using the bindings
> * adding myself and John Kacur to the cpupower section of the maintainers file
> (requested by Shuah Khan)
> * addressed review comments about doc, makefile, and maintainers file
> * small style and other fixes
> 
> The name raw_pylibcpupower is used because a wrapper `pylibcpupower` may be
> needed to make the bindings more 'pythonic' in the future. The bindings folder
> is used because Go or Perl bindings may be useful for other users in the
> future.
> 
> Note that while SWIG itself is GPL v3+ licensed; the resulting output, the
> bindings code, has the same license as the .o files used to generate the
> bindings (GPL v2 only). Please see
> https://swig.org/legal.html
> and
> https://lore.kernel.org/linux-pm/Zqv9BOjxLAgyNP5B@hatbackup/#t
> for more details on the license.
> 
> Sincerely,
> John Wyatt
> Software Engineer, Core Kernel
> Red Hat
> 
> John B. Wyatt IV (4):
>    pm:cpupower: Add missing powercap_set_enabled() stub function
>    pm:cpupower: Add SWIG bindings files for libcpupower
>    pm:cpupower: Include test_raw_pylibcpupower.py
>    MAINTAINERS: Add Maintainers for SWIG Python bindings
> 
>   MAINTAINERS                                   |   3 +
>   .../power/cpupower/bindings/python/.gitignore |   8 +
>   tools/power/cpupower/bindings/python/Makefile |  31 +++
>   tools/power/cpupower/bindings/python/README   |  59 +++++
>   .../bindings/python/raw_pylibcpupower.i       | 247 ++++++++++++++++++
>   .../bindings/python/test_raw_pylibcpupower.py |  42 +++
>   tools/power/cpupower/lib/powercap.c           |   8 +
>   7 files changed, 398 insertions(+)
>   create mode 100644 tools/power/cpupower/bindings/python/.gitignore
>   create mode 100644 tools/power/cpupower/bindings/python/Makefile
>   create mode 100644 tools/power/cpupower/bindings/python/README
>   create mode 100644 tools/power/cpupower/bindings/python/raw_pylibcpupower.i
>   create mode 100755 tools/power/cpupower/bindings/python/test_raw_pylibcpupower.py
> 

Applied the series for Linux 6.12-rc1 to

https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux.git cpupower branch

I chose to walk through the steps without installing SWIG
to see what make would do.

Some things to improve:

Running make in tools/power/cpupower/bindings/python directory without
installing SWIG gives me the following errors:

make: python-config: No such file or directory
swig -python raw_pylibcpupower.i
make: swig: No such file or directory
make: *** [Makefile:27: raw_pylibcpupower_wrap.c] Error 127

I think it would be good to provide better help message walking
user through installing the dependencies.

Documentation/Makefile is a good example to look at for useful
message on the dependencies to be installed.

You can send me patch on top of
https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux.git cpupower branch

thanks,
-- Shuah