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From:   jim.cromie@gmail.com
Date:   Sun, 10 Dec 2023 18:07:11 -0700
Message-ID: <CAJfuBxxYDzL5jkJb6A=sk4qibw4KPrhOvatfBikVqRYx=6WAMA@mail.gmail.com>
Subject: Re: [re: PATCH v2 00/15 - 08/11] dyndbg: split multi-query strings
 with %
To:     =?UTF-8?Q?=C5=81ukasz_Bartosik?= <lb@semihalf.com>
Cc:     linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
        bleung@google.com, contact@emersion.fr, daniel@ffwll.ch,
        dianders@chromium.org, groeck@google.com, jbaron@akamai.com,
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        ppaalanen@gmail.com, rostedt@goodmis.org, seanpaul@chromium.org,
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On Fri, Dec 8, 2023 at 5:32=E2=80=AFPM =C5=81ukasz Bartosik <lb@semihalf.co=
m> wrote:
>
> pt., 8 gru 2023 o 01:15 Jim Cromie <jim.cromie@gmail.com> napisa=C5=82(a)=
:
> >

> >   vng -v --user root -p 4 \
> >       -a dynamic_debug.verbose=3D3 \
> >       -a \*.dyndbg=3Dclass,DRM_UT_CORE,+pfmlt_%class,DRM_UT_KMS,+pfm%cl=
ass,DRM_UT_ATOMIC,+pf
> >
> > ':' would be a more natural multi-cmd separator, but is reserved
> > for +T:<trace_buf> to designate separate tracebuf instances.
> >
> > If '%' is distasteful, the backup plan is ",_,", since that would
> > never appear in a useful <format "$foo"> cmd.
> >
>
> What if we use a different character for passing trace instance name
> to the T flag, for example "-", +T-trace_buf
> and then use ":" instead of "%" as a separator ?
>

*** entering the Bikeshed ***

One of the nice constraints of the flags-val is that it always starts with =
+/-/=3D
the 1st char of flags is the only place they would appear unquoted.
using '-' again dilutes that specialness.

the whole +T:named_stream. syntax has a mnemonic value,
it seems to explain itself (but I'm weird)

WRT to ':' vs '%' as multi-cmd separator, what do we lose in each trade ?
ultimately it invalidates a query containing those chars. IOW

  # impossible query when cmd-splitting on %
  echo format "search for %s because %d" +p > /proc/dynamic_debug/control

  # impossible when splitting on :
  echo format "my_label: " +p > /proc/dynamic_debug/control

NB: only format would see an arg with either : or %, since theyre
*never* in filenames, functions or module (or class) names.

Of the 2, % is even more unlikely to wind up in a name,
colon already appears in host:path and urls,
and in some class-name systems
(tho not planned for "class" keyword)

the ability to search for colon-terminated labels seems more useful
than searching for a particular set of printf format specifiers,
which btw cant have colons between them.