linux-kernel - Re: [PATCH v2 2/3] iio: chemical: Add support for external Reset and Wakeup in CCS811

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Message-ID: <20200414191259.5fbfdc2a@archlinux>
Date:   Tue, 14 Apr 2020 19:12:59 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Manivannan Sadhasivam <mani@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, narcisaanamaria12@...il.com,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald <pmeerw@...erw.net>,
        linux-iio <linux-iio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] iio: chemical: Add support for external Reset
 and Wakeup in CCS811

On Tue, 14 Apr 2020 20:54:49 +0300
Andy Shevchenko <andy.shevchenko@...il.com> wrote:

> On Tue, Apr 14, 2020 at 8:06 PM Manivannan Sadhasivam <mani@...nel.org> wrote:
> > On Tue, Apr 14, 2020 at 07:42:24PM +0300, Andy Shevchenko wrote:  
> > > On Tue, Apr 14, 2020 at 6:34 PM <mani@...nel.org> wrote:  
> 
> ...
> 
> > > > +       reset_gpio = devm_gpiod_get_optional(&client->dev, "reset",
> > > > +                                            GPIOD_OUT_LOW);
> > > > +       if (IS_ERR(reset_gpio)) {  
> > >  
> > > > +               dev_err(&client->dev, "Failed to acquire reset gpio\n");  
> > >
> > > If it's a deferred probe, it would spam the log.
> > >  
> >
> > Hmm. But error is an error isn't it? Would you recommend doing a debug print
> > or completely removing the logging?  
> 
> I would remove completely, but better to wait for Jonathan to comment.
> Maybe he prefers something like
>   if (err != EPROBE_DEFER)
>     dev_err()

Not fussed.  Either drop it or do the check for defer - one I leave up to the
author.

> 
> > > > +               return PTR_ERR(reset_gpio);
> > > > +       }  
> > >
> > > ...
> > >  
> > > > +               static const u8 reset_seq[] = {
> > > > +                       0xFF, 0x11, 0xE5, 0x72, 0x8A,
> > > > +               };  
> > >
> > > I would suggest to comment above from where you got this and the
> > > meaning of the numbers.
> > >  
> >
> > The datasheet doesn't specify the meaning of these values. But will add a
> > comment.  
> 
> Thanks!
> 
> > Btw, just noticed that 0xFF is not needed and only 4 values are
> > sufficient for SW reset.  
> 
> Better to do exactly what datasheet suggests (in case it's not clear
> or deductible what is going on).
>