linux-kernel - Re: [PATCH v3 3/7] mfd: Add base driver for Netronix embedded controller

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Message-ID: <CAHp75VchfQ-djkK6u+fLjq6kfqpzb0nqSLJOe76cb5S3J_F9GQ@mail.gmail.com>
Date:   Tue, 29 Sep 2020 19:37:21 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Jonathan Neuschäfer <j.neuschaefer@....net>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Sam Ravnborg <sam@...nborg.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Heiko Stuebner <heiko.stuebner@...obroma-systems.com>,
        Stephan Gerhold <stephan@...hold.net>,
        Lubomir Rintel <lkundrak@...sk>,
        Mark Brown <broonie@...nel.org>, allen <allen.chen@....com.tw>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        devicetree <devicetree@...r.kernel.org>,
        linux-pwm@...r.kernel.org,
        "open list:REAL TIME CLOCK (RTC) SUBSYSTEM" 
        <linux-rtc@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Josua Mayer <josua.mayer@....eu>,
        Andreas Kemnade <andreas@...nade.info>,
        Arnd Bergmann <arnd@...db.de>, Daniel Palmer <daniel@...f.com>
Subject: Re: [PATCH v3 3/7] mfd: Add base driver for Netronix embedded controller

On Sat, Sep 26, 2020 at 12:32 AM Jonathan Neuschäfer
<j.neuschaefer@....net> wrote:
> On Fri, Sep 25, 2020 at 12:29:45PM +0300, Andy Shevchenko wrote:
> > On Thu, Sep 24, 2020 at 10:26 PM Jonathan Neuschäfer
> > <j.neuschaefer@....net> wrote:

...

> > > +               dev_alert(&poweroff_restart_client->dev,
> > > +                         "Failed to power off (err = %d)\n", res);
> >
> > alert? This needs to be explained.
>
> I copied the dev_alert from drivers/mfd/rn5t618.c.
>
> Upon reconsideration, I'm not sure what the correct log level would be,
> but _warn seems enough, or maybe _err is better

It's up to you to decide, but crit/alert and similar has to be
justified (commit message / comment in the code).

...

> > > +       /*
> > > +        * NOTE: The lower half of the reset value is not sent, because sending
> > > +        * it causes an error
> >
> > Why? Any root cause? Perhaps you need to send 0xffff ?
>
> Unknown, because I don't have the EC firmware for analysis. The vendor
> kernel sends 0xff00 and gets an error.
>
> Sending 0xffff doesn't help.

Maybe a slightly elaborated comment that it's copied from the vendor
kernel (which is?).

> > > +        */

...

> > > +       dev_info(ec->dev,
> > > +                "Netronix embedded controller version %04x detected.\n",
> > > +                version);
> >
> > This info level may confuse users if followed by an error path.
>
> Right. I suppose printing incompatible versions is still useful, so how
> about something like the following?
>
>
>        /* Bail out if we encounter an unknown firmware version */
>        switch (version) {
>        case 0xd726: /* found in Kobo Aura */
>                dev_info(ec->dev,
>                         "Netronix embedded controller version %04x detected.\n",
>                         version);
>                break;
>        default:
>                dev_err(ec->dev,
>                         "Netronix embedded controller version %04x is not supported.\n",
>                         version);
>                return -ENODEV;
>        }

This is better.

...

> > > +               WARN_ON(poweroff_restart_client);
> >
> > WARN_ON? All these alerts, WARNs, BUGs must be explained. Screaming to
> > the user is not good if it wasn't justified.
>
> poweroff_restart_client being already set is not a situation that should
> happen (and would indicate a bug in this driver, AFAICT), but I guess
> the log message could be better in that case...

As per above.

-- 
With Best Regards,
Andy Shevchenko