netdev - Re: [PATCH RESEND net-next 0/5] WWAN debugfs tweaks

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Date:   Sun, 28 Nov 2021 20:27:51 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Sergey Ryazanov <ryazanov.s.a@...il.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        M Chetan Kumar <m.chetan.kumar@...el.com>,
        Intel Corporation <linuxwwan@...el.com>,
        Loic Poulain <loic.poulain@...aro.org>,
        Johannes Berg <johannes@...solutions.net>
Subject: Re: [PATCH RESEND net-next 0/5] WWAN debugfs tweaks

On Sun, Nov 28, 2021 at 03:55:17PM +0300, Sergey Ryazanov wrote:
> Resend with proper target tree. Also I should mention that the series is
> mostly compile-tested since I do not have IOSM supported device, so it
> needs Ack from the IOSM developers.
> 
> This is a follow-up series to just applied IOSM (and WWAN) debugfs
> interface support [1]. The series has two main goals:
> 1. move the driver-specific debugfs knobs to a subdirectory;
> 2. make the debugfs interface optional for both IOSM and for the WWAN
>    core.
> 
> As for the first part, I must say that it was my mistake. I suggested to
> place debugfs entries under a common per WWAN device directory. But I
> missed the driver subdirectory in the example, so it become:
> 
> /sys/kernel/debugfs/wwan/wwan0/trace
> 
> Since the traces collection is a driver-specific feature, it is better
> to keep it under the driver-specific subdirectory:
> 
> /sys/kernel/debugfs/wwan/wwan0/iosm/trace
> 
> It is desirable to be able to entirely disable the debugfs interface. It
> can be disabled for several reasons, including security and consumed
> storage space.

When such needs arise, the disable is done with CONFIG_DEBUGFS knob and
not with per-subsystem configs.

I personally see your CONFIG_*_DEBUGFS patches as a mistake, which
complicates code without any gain at all. Even an opposite is true,
by adding more knobs, you can find yourself with the system which
has CONFIG_DEBUGFS enabled but with your CONFIG_*_DEBUGFS disabled.

Thanks