Received-SPF: pass (google.com: domain of linux-kernel+bounces-205836-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
Message-ID: <a6c7e97b80e3448a40be95ef7aab0e0e74026edc.camel@gmail.com>
Subject: Re: [PATCH v6 9/9] iio: adc: ad7173: Add support for AD411x devices
From: Nuno =?ISO-8859-1?Q?S=E1?= <noname.nuno@gmail.com>
To: "Ceclan, Dumitru" <mitrutzceclan@gmail.com>, dumitru.ceclan@analog.com
Cc: Lars-Peter Clausen <lars@metafoo.de>, Michael Hennerich
 <Michael.Hennerich@analog.com>, Jonathan Cameron <jic23@kernel.org>, Rob
 Herring <robh@kernel.org>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@linaro.org>, Conor Dooley <conor+dt@kernel.org>,
 David Lechner <dlechner@baylibre.com>,  linux-iio@vger.kernel.org,
 devicetree@vger.kernel.org,  linux-kernel@vger.kernel.org
Date: Fri, 07 Jun 2024 12:39:02 +0200
In-Reply-To: <1c6d409b-ba9e-4a19-a6cb-e06209a24154@gmail.com>
References: <20240606-ad4111-v6-0-573981fb3e2e@analog.com>
	 <20240606-ad4111-v6-9-573981fb3e2e@analog.com>
	 <389546877ae11b18928b432e86710acf83974f67.camel@gmail.com>
	 <1c6d409b-ba9e-4a19-a6cb-e06209a24154@gmail.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.52.2 
Precedence: bulk
MIME-Version: 1.0

On Fri, 2024-06-07 at 12:41 +0300, Ceclan, Dumitru wrote:
> On 07/06/2024 12:20, Nuno S=C3=A1 wrote:
> > On Thu, 2024-06-06 at 19:07 +0300, Dumitru Ceclan via B4 Relay wrote:
> > > From: Dumitru Ceclan <dumitru.ceclan@analog.com>
> > >=20
> > > Add support for AD4111/AD4112/AD4114/AD4115/AD4116.
> > >=20
> > > The AD411X family encompasses a series of low power, low noise, 24-bi=
t,
> > > sigma-delta analog-to-digital converters that offer a versatile range=
 of
> > > specifications.
> > >=20
> > > This family of ADCs integrates an analog front end suitable for proce=
ssing
> > > both fully differential and single-ended, bipolar voltage inputs
> > > addressing a wide array of industrial and instrumentation requirement=
s.
> > >=20
> > > - All ADCs have inputs with a precision voltage divider with a divisi=
on
> > > =C2=A0 ratio of 10.
> > > - AD4116 has 5 low level inputs without a voltage divider.
> > > - AD4111 and AD4112 support current inputs (0 mA to 20 mA) using a 50=
ohm
> > > =C2=A0 shunt resistor.
> > >=20
> > > Signed-off-by: Dumitru Ceclan <dumitru.ceclan@analog.com>
> > > ---
> > > =C2=A0drivers/iio/adc/ad7173.c | 317
> > > ++++++++++++++++++++++++++++++++++++++++++----
> > > -
> > > =C2=A01 file changed, 285 insertions(+), 32 deletions(-)
> > >=20
> > > diff --git a/drivers/iio/adc/ad7173.c b/drivers/iio/adc/ad7173.c
> > > index 58da5717fd36..cfcd12447e24 100644
> > > --- a/drivers/iio/adc/ad7173.c
> > > +++ b/drivers/iio/adc/ad7173.c
> > >=20
> > ...
> >=20
> > > =C2=A0static const struct ad7173_device_info ad7172_2_device_info =3D=
 {
> > > =C2=A0	.name =3D "ad7172-2",
> > > =C2=A0	.id =3D AD7172_2_ID,
> > > -	.num_inputs =3D 5,
> > > +	.num_voltage_in =3D 5,
> > > =C2=A0	.num_channels =3D 4,
> > > =C2=A0	.num_configs =3D 4,
> > > =C2=A0	.num_gpios =3D 2,
> > > +	.higher_gpio_bits =3D false,
> >=20
> > No need to explicitly set to 'false'. Ditto for the other places...
> >=20
> > ...
> >=20
> > >=20
> > > =C2=A0static int ad7173_validate_voltage_ain_inputs(struct ad7173_sta=
te *st,
> > > =C2=A0					=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 unsigned int ain0, unsigned
> > > int
> > > ain1)
> > > =C2=A0{
> > > @@ -946,15 +1145,30 @@ static int
> > > ad7173_validate_voltage_ain_inputs(struct
> > > ad7173_state *st,
> > > =C2=A0	=C2=A0=C2=A0=C2=A0 st->info->has_pow_supply_monitoring)
> > > =C2=A0		return 0;
> > > =C2=A0
> > > -	special_input0 =3D AD7173_IS_REF_INPUT(ain0);
> > > -	special_input1 =3D AD7173_IS_REF_INPUT(ain1);
> > > +	special_input0 =3D AD7173_IS_REF_INPUT(ain0) ||
> > > +			 (ain0 =3D=3D AD4111_VINCOM_INPUT && st->info-
> > > > has_vincom_input);
> > > +	special_input1 =3D AD7173_IS_REF_INPUT(ain1) ||
> > > +			 (ain1 =3D=3D AD4111_VINCOM_INPUT && st->info-
> > > > has_vincom_input);
> > > +
> >=20
> > Wondering... can ain1 (or ain0) be AD4111_VINCOM_INPUT and !st->info-
> > > has_vincom_input? Would that actually be acceptable? It would assume =
it's
> > > not
> > so we should check that right? Or am I missing something?
> >=20
> > - Nuno S=C3=A1
> >=20
>=20
> It will fail when we check for the number of voltage inputs:
> (ain0 >=3D st->info->num_voltage_in && !special_input0)=20
> as special_input will not be true if has_vincom_input is false
>=20
> Indeed this check is a bit hidden, should it be more explicit?
>=20

Hmm I see... Up to you. I guess I was not paying enough attention to=C2=A0
st->info->num_voltage_in and to the fact that VINCOM and REFs are not count=
ed by
it.

OTOH, yes, an explicit check could make sense because the log you output:

"Input pin number out of range for pair..."

It's really not mentioning the real problem (or it's a very hidden message =
IOW).
having something like

if (ain0 =3D=3D AD4111_VINCOM_INPUT && !st->info-has_vincom_input)
	return dev_err_probe(dev, -EINVAL, "VINCOM not supported for %s\n",
			part_name);

would be something way easier to understand :)

- Nuno S=C3=A1