linux-kernel - Re: [re: PATCH v2 00/15 - 05/11] dyndbg: change +T:name

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Date: Mon, 18 Dec 2023 18:29:56 +0100
From: Petr Mladek <pmladek@...e.com>
To: Jim Cromie <jim.cromie@...il.com>
Cc: lb@...ihalf.com, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, bleung@...gle.com, contact@...rsion.fr,
	daniel@...ll.ch, dianders@...omium.org, groeck@...gle.com,
	jbaron@...mai.com, john.ogness@...utronix.de, keescook@...omium.org,
	ppaalanen@...il.com, rostedt@...dmis.org, seanpaul@...omium.org,
	sergey.senozhatsky@...il.com, upstream@...ihalf.com,
	vincent.whitchurch@...s.com, yanivt@...gle.com,
	gregkh@...uxfoundation.org
Subject: Re: [re: PATCH v2 00/15 -  05/11] dyndbg: change +T:name_terminator
 to dot

On Thu 2023-12-07 17:15:08, Jim Cromie wrote:
> This replaces ',' with '.' as the char that ends the +T:name.
> 
> This allows a later patch to treat ',' as a space, which mostly
> eliminates the need to quote query/rules.  And this in turn avoids
> quoting hassles:
> 
>   modprobe test_dynamic_debug dyndbg=class,D2_CORE,+p
> 
> It is particularly good for passing boot-args into test-scripts.
> 
>   vng -p 4 -v \
>   -a test_dynamic_debug.dyndbg=class,D2_CORE,+p

Could you please add example how it looked before and after?
Is this format documented somewhere?
Will the documentation get updated?
Could it break existing scripts? [*]

The dynamic debug interface is really hard to use for me
as an occasional user. I always have to look into
Documentation/admin-guide/dynamic-debug-howto.rst

Anyway, there should be a good reason to change the interface.
And the exaplantion:

   "Let's use '.' instead of ',' so that we could later
    treat ',' as space"

sounds scarry. It does not explain what is the advantage at all.


[*] Some scripts are using the interface even in the mainline,
for example:

$> git grep "dynamic_debug" tools/testing/
tools/testing/selftests/bpf/test_tunnel.sh:     echo 'file ip_gre.c +p' > /sys/kernel/debug/dynamic_debug/control
tools/testing/selftests/bpf/test_tunnel.sh:     echo 'file ip6_gre.c +p' > /sys/kernel/debug/dynamic_debug/control
tools/testing/selftests/bpf/test_tunnel.sh:     echo 'file geneve.c +p' > /sys/kernel/debug/dynamic_debug/control
tools/testing/selftests/bpf/test_tunnel.sh:     echo 'file ipip.c +p' > /sys/kernel/debug/dynamic_debug/control
tools/testing/selftests/livepatch/functions.sh: DYNAMIC_DEBUG=$(grep '^kernel/livepatch' /sys/kernel/debug/dynamic_debug/control | \
tools/testing/selftests/livepatch/functions.sh:         echo -n "$DYNAMIC_DEBUG" > /sys/kernel/debug/dynamic_debug/control
tools/testing/selftests/livepatch/functions.sh:function set_dynamic_debug() {
tools/testing/selftests/livepatch/functions.sh:        cat <<-EOF > /sys/kernel/debug/dynamic_debug/control
tools/testing/selftests/livepatch/functions.sh: set_dynamic_debug


Best Regards,
Petr