linux-kernel - Re: [PATCH] arm: exynos_config: Restore debugfs support

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Message-ID: <CAJKOXPept5Po3UDfLWCTYEupiip-Y6ZXtdaOGTQd8K-6m11DbA@mail.gmail.com>
Date:   Tue, 26 Nov 2019 09:21:27 +0800
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     Kusanagi Kouichi <slash@...auone-net.jp>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        "linux-samsung-soc@...r.kernel.org" 
        <linux-samsung-soc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm: exynos_config: Restore debugfs support

On Mon, 25 Nov 2019 at 23:31, Bartlomiej Zolnierkiewicz
<b.zolnierkie@...sung.com> wrote:
>
>
> On 11/25/19 3:39 PM, Steven Rostedt wrote:
> > On Mon, 25 Nov 2019 15:30:39 +0100
> > Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com> wrote:
> >
> >> It seems that commit 0e4a459f56c3 ("tracing: Remove unnecessary DEBUG_FS
> >> dependency") disabled DEBUG_FS also in some other ARM defconfigs.
> >>
> >> For some of them it may be a correct change but a preferred way to
> >> introduce such changes would be to:
> >>
> >> - add explicit CONFIG_DEBUG_FS=y instances to all affected defconfigs
> >>   while removing DEBUG_FS selection from TRACING config item
> >>
> >
> > I strongly disagree. It was wrong to assume DEBUG_FS is attached to
> > TRACING. If someone wanted DEBUG_FS in their def config, they should
> > have added it specifically. The addition of DEBUG_FS to defconfigs no
>
> There is a theory and a practice.
>
> In theory you are are correct. ;-)
>
> In practice people don't manually edit configuration files nowadays.
>
> They do 'make menuconfig' and enable what they need and disable what
> they do not need.  Then they do 'make savedefconfig' and copy resulting
> "stripped" defconfig file as their new platform defconfig. As a result
> defconfigs rely on many default settings (also they explicitly disable
> only items that are enabled by default but you don't want them).

I agree with Bartłomiej. Your interpretation Steven essentially
prohibits any use of savedefconfig to trim automatically the config
from unneeded options. Therefore many defconfigs which do not have
DEBUG_FS or other options directly, but they want it.

Some time ago I had patches removing specific non-existing options
from defconfigs. For each option I provided a rationale that it is
gone/etc so let's remove it from defconfig. Most of maintainers picked
them up but few (2-3?) instead run savedefconfig to clean up
everything automatically.

Best regards,
Krzysztof