netdev - Re: [PATCH bpf-next v2 1/3] tools: bpftool: add -d option to get debug output from libbpf

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Message-ID: <c720f3ce-059b-b47a-a0de-5e360b590a30@netronome.com>
Date:   Fri, 24 May 2019 10:46:55 +0100
From:   Quentin Monnet <quentin.monnet@...ronome.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, bpf@...r.kernel.org,
        Networking <netdev@...r.kernel.org>, oss-drivers@...ronome.com,
        Yonghong Song <yhs@...com>
Subject: Re: [PATCH bpf-next v2 1/3] tools: bpftool: add -d option to get
 debug output from libbpf

2019-05-23 13:57 UTC-0700 ~ Andrii Nakryiko <andrii.nakryiko@...il.com>
> On Thu, May 23, 2019 at 1:44 PM Jakub Kicinski
> <jakub.kicinski@...ronome.com> wrote:
>>
>> On Thu, 23 May 2019 09:20:52 -0700, Andrii Nakryiko wrote:
>>> On Thu, May 23, 2019 at 3:54 AM Quentin Monnet wrote:
>>>>
>>>> libbpf has three levels of priority for output messages: warn, info,
>>>> debug. By default, debug output is not printed to the console.
>>>>
>>>> Add a new "--debug" (short name: "-d") option to bpftool to print libbpf
>>>> logs for all three levels.
>>>>
>>>> Internally, we simply use the function provided by libbpf to replace the
>>>> default printing function by one that prints logs regardless of their
>>>> level.
>>>>
>>>> v2:
>>>> - Remove the possibility to select the log-levels to use (v1 offered a
>>>>   combination of "warn", "info" and "debug").
>>>> - Rename option and offer a short name: -d|--debug.
>>>
>>> Such and option in CLI tools is usually called -v|--verbose, I'm
>>> wondering if it might be a better name choice?
>>>
>>> Btw, some tools also use -v, -vv and -vvv to define different levels
>>> of verbosity, which is something we can consider in the future, as
>>> it's backwards compatible.
>>
>> That was my weak suggestion.  Sometimes -v is used for version, e.g.
>> GCC.  -d is sometimes used for debug, e.g. man, iproute2 uses it as
>> short for "detailed".  If the consensus is that -v is better I don't
>> really mind.
> 
> It's minor, so I'm not insisting at all, just wasn't sure it was
> brought up. bpftool is sufficiently different in its conventions from
> other modern CLIs anyways.
> 
> As for -v for version. It seems like the trend is to use -V|--version
> for version, and -v|--verbose for verbosity. I've also seen some tools
> option for `cli version` (subcommand) for version. Anyway, no strong
> preferences from me either.
> 

For the record, bpftool has both "bpftool -V" and "bpftool version" to
dump the version number.

This leaves us with "-v" free to do something like "--verbose", but just
as Jakub said we wanted to limit the risks of confusion... I don't mind
changing, but since nobody has expressed a strong opinion on the matter,
I'll stick to "-d|--debug" for now.

Thanks Andrii for the review!
Quentin