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

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Date:   Sat, 3 Oct 2020 00:54:08 +0200
From:   Jonathan Neuschäfer <j.neuschaefer@....net>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Jonathan Neuschäfer <j.neuschaefer@....net>,
        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 Tue, Sep 29, 2020 at 07:37:21PM +0300, Andy Shevchenko wrote:
> 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).

Alright, thanks for explaining.

> > > > +       /*
> > > > +        * 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?).

Good idea, I'll do that.

> ...
> 
> > > > +       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.

Okay, I'll rework the dev_alert/WARN_ON parts.



Thanks,
Jonathan Neuschäfer

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