linux-kernel - Re: [PATCH v3 2/3] pinctrl: core: configure pinmux from pins debug file

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Date:   Fri, 21 May 2021 09:44:06 +0300
From:   Vladimir Zapolskiy <vz@...ia.com>
To:     Dario Binacchi <dariobin@...ero.it>, linux-kernel@...r.kernel.org
Cc:     Tony Lindgren <tony@...mide.com>,
        Drew Fustini <drew@...gleboard.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-gpio@...r.kernel.org
Subject: Re: [PATCH v3 2/3] pinctrl: core: configure pinmux from pins debug
 file

Hello Dario,

On 5/20/21 11:27 PM, Dario Binacchi wrote:
> The MPUs of some architectures (e.g AM335x) must be in privileged
> operating mode to write on the pinmux registers. In such cases, where
> writes will not work from user space, now it can be done from the pins

user space has no connection to the problem you're trying to solve.

Please provide a reasonable rationale for adding a new interface, thank
you in advance.

> debug file if the platform driver exports the pin_dbg_set() helper among
> the registered operations.
> 
> Signed-off-by: Dario Binacchi <dariobin@...ero.it>

I strongly object against this new interface.

As Andy've already mentioned you have to operate with defined pin groups
and functions, and so far you create an interface with an option to
disasterous misusage, it shall be avoided, because there are better
options.

What's the issue with a regular declaration of pin groups and functions
on your SoC? When it's done, you can operate on this level of abstraction,
there is absolutely no need to add the proposed low-level debug interface.

--
Best wishes,
Vladimir