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Date: Mon, 19 Feb 2024 19:46:50 +0000
From: Jonathan Cameron <jic23@kernel.org>
To: David Lechner <dlechner@baylibre.com>
Cc: linux-iio@vger.kernel.org, Michael Hennerich
 <Michael.Hennerich@analog.com>, Rob Herring <robh+dt@kernel.org>, Krzysztof
 Kozlowski <krzysztof.kozlowski+dt@linaro.org>, Conor Dooley
 <conor+dt@kernel.org>, Nuno =?UTF-8?B?U8Oh?= <nuno.sa@analog.com>, Liam
 Girdwood <lgirdwood@gmail.com>, Mark Brown <broonie@kernel.org>,
 devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] iio: adc: ad7944: add driver for
 AD7944/AD7985/AD7986
Message-ID: <20240219194650.3e14c877@jic23-huawei>
In-Reply-To: <CAMknhBH2Pqa9xpPxnTCxJegVTbOG-QDeJA4YrQUPfj+hfSs73A@mail.gmail.com>
References: <20240216-ad7944-mainline-v2-0-7eb69651e592@baylibre.com>
	<20240216-ad7944-mainline-v2-2-7eb69651e592@baylibre.com>
	<CAMknhBH2Pqa9xpPxnTCxJegVTbOG-QDeJA4YrQUPfj+hfSs73A@mail.gmail.com>
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On Mon, 19 Feb 2024 13:13:35 -0600
David Lechner <dlechner@baylibre.com> wrote:

> On Fri, Feb 16, 2024 at 1:47=E2=80=AFPM David Lechner <dlechner@baylibre.=
com> wrote:
>=20
> ...
>=20
> > +
> > +#define AD7944_DEFINE_CHIP_INFO(_name, _t, _bits, _sign)              =
 \
> > +static const struct ad7944_chip_info _name##_chip_info =3D {          =
   \
> > +       .name =3D #_name,                                              =
   \
> > +       .t =3D &_t##_timing_spec,                                      =
   \
> > +       .channels =3D {                                                =
   \
> > +               {                                                      =
 \
> > +                       .type =3D IIO_VOLTAGE,                         =
   \
> > +                       .indexed =3D 1,                                =
   \
> > +                       .differential =3D 1,                           =
   \
> > +                       .channel =3D 0,                                =
   \
> > +                       .channel2 =3D 1,                               =
   \
> > +                       .scan_index =3D 0,                             =
   \
> > +                       .scan_type.sign =3D _sign,                     =
   \
> > +                       .scan_type.realbits =3D _bits,                 =
   \
> > +                       .scan_type.storagebits =3D _bits > 16 ? 32 : 16=
,  \
> > +                       .scan_type.endianness =3D IIO_CPU,             =
   \
> > +                       .info_mask_separate =3D BIT(IIO_CHAN_INFO_RAW) =
   \
> > +                                       | BIT(IIO_CHAN_INFO_SCALE),    =
 \
> > +               },                                                     =
 \
> > +               IIO_CHAN_SOFT_TIMESTAMP(1),                            =
 \
> > +       },                                                             =
 \
> > +}
> > +
> > +AD7944_DEFINE_CHIP_INFO(ad7944, ad7944, 14, 'u');
> > +AD7944_DEFINE_CHIP_INFO(ad7985, ad7944, 16, 'u');
> > +AD7944_DEFINE_CHIP_INFO(ad7986, ad7986, 18, 's'); =20
>=20
> Now that I have been enlightened [1] about pseudo-differntial inputs,
> I'm thinking that AD7944 and AD7985 should not have the .differential
> =3D 1 flag set since they are pseudo-differential inputs with a ground
> sense on the negative input (and no extra supply needed since it is
> always ground). Does that sound right?

yes

>=20
> AD7986 is true differential though, so should be correct already.
>=20
> [1]: https://lore.kernel.org/linux-iio/CAMknhBF5mAsN1c-194Qwa5oKmqKzef2kh=
XnqA1cSdKpWHKWp0w@mail.gmail.com/