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References: <20240311-mainline-ad7944-3-wire-mode-v1-1-8e8199efa1f7@baylibre.com>
 <8ee551edeff9c4c959a4dbda53d1a2a26a9bb62c.camel@gmail.com>
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From: David Lechner <dlechner@baylibre.com>
Date: Tue, 12 Mar 2024 09:13:56 -0500
Message-ID: <CAMknhBE8OwrtbJ9xYVZ8ObsZTnxmn9Fpk2a-gj1aCSaN-whDRg@mail.gmail.com>
Subject: Re: [PATCH] iio: adc: ad7944: Add support for "3-wire mode"
To: =?UTF-8?B?TnVubyBTw6E=?= <noname.nuno@gmail.com>
Cc: Jonathan Cameron <jic23@kernel.org>, Michael Hennerich <michael.hennerich@analog.com>, 
	=?UTF-8?B?TnVubyBTw6E=?= <nuno.sa@analog.com>, linux-iio@vger.kernel.org, 
	linux-kernel@vger.kernel.org
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On Tue, Mar 12, 2024 at 4:08=E2=80=AFAM Nuno S=C3=A1 <noname.nuno@gmail.com=
> wrote:
>
> On Mon, 2024-03-11 at 16:26 -0500, David Lechner wrote:

..

> >  /*
> >   * ad7944_4wire_mode_conversion - Perform a 4-wire mode conversion and=
 acquisition
> >   * @adc: The ADC device structure
> > @@ -167,9 +246,22 @@ static int ad7944_single_conversion(struct ad7944_=
adc *adc,
> >  {
> >       int ret;
> >
> > -     ret =3D ad7944_4wire_mode_conversion(adc, chan);
> > -     if (ret)
> > -             return ret;
> > +     switch (adc->spi_mode) {
> > +     case AD7944_SPI_MODE_DEFAULT:
> > +             ret =3D ad7944_4wire_mode_conversion(adc, chan);
> > +             if (ret)
> > +                     return ret;
> > +
> > +             break;
> > +     case AD7944_SPI_MODE_SINGLE:
> > +             ret =3D ad7944_3wire_cs_mode_conversion(adc, chan);
> > +             if (ret)
> > +                     return ret;
> > +
> > +             break;
> > +     case AD7944_SPI_MODE_CHAIN:
> > +             return -EOPNOTSUPP;
>
> This mode is not really supported for now and in theory we can't really h=
ave
> adc->spi_mode =3D AD7944_SPI_MODE_CHAIN, right? So, I would just make thi=
s the
> 'default' branch and not care about chain mode (implementing it when addi=
ng it).

The compiler was happy with this, but yeah, default: is probably safer.

..

> > +     if (!adc->cnv && adc->spi_mode =3D=3D AD7944_SPI_MODE_DEFAULT)
> > +             return dev_err_probe(&spi->dev, -EINVAL, "CNV GPIO is
> > required\n");
> > +     else if (adc->cnv && adc->spi_mode !=3D AD7944_SPI_MODE_DEFAULT)
> > +             return dev_err_probe(&spi->dev, -EINVAL,
> > +                                  "CNV GPIO in single and chain mode i=
s not
> > currently supported\n");
> > +
>
> Redundant else...

yup

>
> >       adc->turbo =3D devm_gpiod_get_optional(dev, "turbo", GPIOD_OUT_LO=
W);
> >       if (IS_ERR(adc->turbo))
> >               return dev_err_probe(dev, PTR_ERR(adc->turbo),
> > @@ -369,6 +486,10 @@ static int ad7944_probe(struct spi_device *spi)
> >               return dev_err_probe(dev, -EINVAL,
> >                       "cannot have both turbo-gpios and adi,always-turb=
o\n");
> >
> > +     if (adc->spi_mode =3D=3D AD7944_SPI_MODE_CHAIN && adc->always_tur=
bo)
> > +             return dev_err_probe(dev, -EINVAL,
> > +                     "cannot have both chain mode and always turbo\n")=
;
> > +
>
>
> I'm fine in having this now but shouldn't we only have the above when we =
do support
> chain mode? A bit odd having it when we don't even allow chain mode.
>

Yeah, we could wait to add this. It seemed like something easy to
overlook though if we don't add chain mode right away, so I just went
ahead and added it now.