Re: [dpdk-dev] [PATCH RFC] devtools: increase default line length to 100

[Bruce Richardson <bruce.richardson@intel.com>]

On Wed, Jun 10, 2020 at 12:28:53PM +0300, Andrew Rybchenko wrote:
> On 6/10/20 11:47 AM, Jerin Jacob wrote:
> > On Wed, Jun 10, 2020 at 1:57 PM Andrew Rybchenko
> > <arybchenko@solarflare.com> wrote:
> >>
> >> On 6/10/20 8:22 AM, Jerin Jacob wrote:
> >>> On Tue, Jun 9, 2020 at 7:27 PM Bruce Richardson
> >>> <bruce.richardson@intel.com> wrote:
> >>>>
> >>>> On Tue, Jun 09, 2020 at 04:40:28PM +0300, Andrew Rybchenko wrote:
> >>>>> On 6/9/20 1:00 PM, Ananyev, Konstantin wrote:
> >>>>>>
> >>>>>>>
> >>>>>>> On Mon, Jun 08, 2020 at 12:17:23PM -0700, Stephen Hemminger wrote:
> >>>>>>>> On Mon,  8 Jun 2020 17:46:40 +0100 Bruce Richardson
> >>>>>>>> <bruce.richardson@intel.com> wrote:
> >>>>>>>>
> >>>>>>>>> Rather than continuing to recommend an 80-char line limit, let's
> >>>>>>>>> take a hint from the Linux kernel[1] and aim for an 100-char
> >>>>>>>>> recommended limit instead.
> >>>>>>>>>
> >>>>>>>>> [1]
> >>>>>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=bdc48fa11e46f867ea4d75fa59ee87a7f48be144
> >>>>>>>>>
> >>>>>>>>> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com> ---
> >>>>>>>>> devtools/checkpatches.sh                 | 2 +-
> >>>>>>>>> doc/guides/contributing/coding_style.rst | 2 +- 2 files changed, 2
> >>>>>>>>> insertions(+), 2 deletions(-)
> >>>>>>>>>
> >>>>>>>>> diff --git a/devtools/checkpatches.sh b/devtools/checkpatches.sh
> >>>>>>>>> index 158087f1c..4970ed830 100755 --- a/devtools/checkpatches.sh +++
> >>>>>>>>> b/devtools/checkpatches.sh @@ -15,7 +15,7 @@
> >>>>>>>>> VALIDATE_NEW_API=$(dirname $(readlink -f $0))/check-symbol-change.sh
> >>>>>>>>> # Codespell can also be enabled by setting DPDK_CHECKPATCH_CODESPELL
> >>>>>>>>> to a valid path # to a dictionary.txt file if dictionary.txt is not
> >>>>>>>>> in the default location.
> >>>>>>>>> codespell=${DPDK_CHECKPATCH_CODESPELL:-enable}
> >>>>>>>>> -length=${DPDK_CHECKPATCH_LINE_LENGTH:-80}
> >>>>>>>>> +length=${DPDK_CHECKPATCH_LINE_LENGTH:-100}
> >>>>>>>>>
> >>>>>>>>>  # override default Linux options options="--no-tree" diff --git
> >>>>>>>>>  a/doc/guides/contributing/coding_style.rst
> >>>>>>>>>  b/doc/guides/contributing/coding_style.rst index
> >>>>>>>>>  4efde93f6..1db3a7bbe 100644 ---
> >>>>>>>>>  a/doc/guides/contributing/coding_style.rst +++
> >>>>>>>>>  b/doc/guides/contributing/coding_style.rst @@ -21,7 +21,7 @@ The
> >>>>>>>>>  rules and guidelines given in this document cannot cover every
> >>>>>>>>>  situation, so * In the case of creating new files, the style should
> >>>>>>>>>  be consistent within each file in a given directory or module.  *
> >>>>>>>>>  The primary reason for coding standards is to increase code
> >>>>>>>>>  readability and comprehensibility, therefore always use whatever
> >>>>>>>>>  option
> >>>>>>> will make the code easiest to read.
> >>>>>>>>>
> >>>>>>>>> -Line length is recommended to be not more than 80 characters,
> >>>>>>>>> including comments.  +Line length is recommended to be not more than
> >>>>>>>>> 100 characters, including comments.  [Tab stop size should be
> >>>>>>>>> assumed to be 8-characters wide].
> >>>>>>>>>
> >>>>>>>>>  .. note::
> >>>>>>>>
> >>>>>>>> I would even support going to 120 characters.
> >>>>>>>>
> >>>>>>>> Acked-by: Stephen Hemminger <stephen@networkplumber.org>
> >>>>>>>
> >>>>>>> I think 100 is enough.
> >>>>>>>
> >>>>>>> In my case, I have a 1080p 24" monitor, and with two terminals
> >>>>>>> side-by-side 100 characters just fits inside each vim window. Going to
> >>>>>>> 120 would be fine for single terminal at a time, but I would find
> >>>>>>> awkward for e.g.  side-by-side diff comparison in meld etc.
> >>>>>>
> >>>>>> My preference would be to keep things as it is - 80 chars per line.
> >>>>>> Having multiple different formatting styles in one source file looks
> >>>>>> really awkward and make it hard to follow.
> >>>>>
> >>>>> +1
> >>>>>
> >>>> I wouldn't personally consider increasing the max line length as a style
> >>>> change, but even if you consider it such I'd worry about rejecting style
> >>>> changes on the basis that it may be different to what is there before. That
> >>>> logic means that we can never, ever change any element of DPDK coding style.
> >>>>
> >>>> I can see the issue with changes that require us to rework the style of
> >>>> code in order to comply with the new style, but changing the max length
> >>>> from 80 to 100 does not make 80-char lines incorrect and needing changes.
> >>>
> >>> Another point is: Other projects derived from the Linux kernel coding
> >>> standard also
> >>> getting migrated to the new coding standard. This change would be useful for:
> >>> a) People works on multiple Linux coding standard derived projects
> >>
> >> Valid point, but not really strong.
> >> I think that .editorconfig solves it.
> > 
> > Yes, For adding the code. I meaning, Viewing the code there will be a disparity.
> 
> I hope you're not suggesting to reformat all existing code.
> Otherwise the disparity will be there for a long-long time
> anyway.
> 
> >>
> >>> b) Some of the code such as 'base' and 'common' code for HW drivers
> >>> are shared between multiple projects.
> >>> Such code needs adjustment/change when pulling to the DPDK code base
> >>> it it still follows 80 chars per line.
> >>
> >> Base and common code are not required to follow DPDK coding
> >> style even now.
> > 
> > I see, I dont think it is expressed in devtools/checkpatches.sh. I.e
> > CI tools still flag as checkpatch issues.
> 
> Yes, it is an area which should be improved.
> 
> > Coming to original concern:(code disparity with existing code)
> > Another option is, It is possible to change existing code to 100 lines
> > with clang-format in an automatic fashion. But it will have a lot of
> > changes.
> >         "C_Cpp.clang_format_style": "{ BasedOnStyle: LLVM,
> > IndentWidth: 8, TabWidth: 8, UseTab: Always,
> > AllowShortIfStatementsOnASingleLine: false, IndentCaseLabels: false,
> > ColumnLimit: 100, AllowShortFunctionsOnASingleLine: false,
> > AlwaysBreakAfterReturnType: AllDefinitions, ColumnLimit: 100,
> > ConstructorInitializerAllOnOneLineOrOnePerLine: true,
> > ConstructorInitializerIndentWidth: 8, ContinuationIndentWidth: 8,
> > BreakBeforeBraces: Linux, AllowShortBlocksOnASingleLine: false,
> > AlignConsecutiveAssignments: false, AlignEscapedNewlines: Right,
> > AlignConsecutiveMacros : true, MaxEmptyLinesToKeep : 1,
> > Cpp11BracedListStyle : true, AlignTrailingComments : true,
> > ForEachMacros: ['TAILQ_FOREACH_SAFE', STAILQ_FOREACH',
> > 'rte_graph_foreach_node', 'TAILQ_FOREACH', 'RTE_ETH_FOREACH_DEV']}",
> 
> No, no, no. Please, no. It will complicate backporting a lot,
> it will break (over-complicate) git blame.
> (I hope it was suggested just to be sure that it will not be
> done).

+1 for this. I don't think we can ever take any style changes into DPDK
which require us to reformat all our existing code.

Thankfully, as I've stated before, this is not such a change, since code
which is under 80 chars long is also under 100 chars long so no issue. :-)