linux-kernel - Re: [PATCH v3 3/3] pinctrl: single: set pinmux from pins debug file

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Date:   Fri, 21 May 2021 09:44:09 +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>,
        Haojian Zhuang <haojian.zhuang@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-gpio@...r.kernel.org,
        linux-omap@...r.kernel.org
Subject: Re: [PATCH v3 3/3] pinctrl: single: set pinmux from pins debug file

Hello Dario,

On 5/20/21 11:27 PM, Dario Binacchi wrote:
> As described in section 9.1 of the TI reference manual for AM335x [1],
> "For writing to the control module registers, the MPU will need to be in
> privileged mode of operation and writes will not work from user mode".
> By adding the pin_dbg_set helper to pcs_pinctrl_ops it will be possible
> to write these registers from the pins debug:

this makes little sense, because it should be possible to write to the
registers without introduction of this interface, pin group/function
is the right level of abstraction for your particular task.

> cd /sys/kernel/debug/pinctrl/44e10800.pinmux-pinctrl-single/
> echo <pin-number> <reg-value> >pins
> 
> [1] https://www.ti.com/lit/ug/spruh73q/spruh73q.pdf
> 
> Signed-off-by: Dario Binacchi <dariobin@...ero.it>

I strongly object against this new interface to be added.

--
Best wishes,
Vladimir