linux-kernel - Re: [PATCH 2/4] iio: adc: Add support for the Renesas RZ/N1 ADC

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Message-ID: <20251017095936.71cb318b@bootlin.com>
Date: Fri, 17 Oct 2025 09:59:36 +0200
From: Herve Codina <herve.codina@...tlin.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Wolfram Sang <wsa+renesas@...g-engineering.com>, Jonathan Cameron
 <jic23@...nel.org>, David Lechner <dlechner@...libre.com>, Nuno
 Sá <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Geert Uytterhoeven
 <geert+renesas@...der.be>, Magnus Damm <magnus.damm@...il.com>, Liam
 Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
 linux-iio@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, Pascal Eberhard
 <pascal.eberhard@...com>, Miquel Raynal <miquel.raynal@...tlin.com>, Thomas
 Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 2/4] iio: adc: Add support for the Renesas RZ/N1 ADC

Hi Geert,

On Fri, 17 Oct 2025 09:40:42 +0200
Geert Uytterhoeven <geert@...ux-m68k.org> wrote:

> Hi Hervé,
> 
> On Fri, 17 Oct 2025 at 09:37, Herve Codina <herve.codina@...tlin.com> wrote:
> > Wolfram Sang <wsa+renesas@...g-engineering.com> wrote:  
> > > On Wed, Oct 15, 2025 at 04:28:14PM +0200, Herve Codina (Schneider Electric) wrote:  
> > > > +static void rzn1_adc_vc_setup_conversion(struct rzn1_adc *rzn1_adc, u32 ch,
> > > > +                                    int adc1_ch, int adc2_ch)
> > > > +{
> > > > +   u32 vc = 0;
> > > > +
> > > > +   if (adc1_ch != -1)
> > > > +           vc |= RZN1_ADC_VC_ADC1_ENABLE | RZN1_ADC_VC_ADC1_CHANNEL_SEL(adc1_ch);
> > > > +
> > > > +   if (adc2_ch != -1)
> > > > +           vc |= RZN1_ADC_VC_ADC2_ENABLE | RZN1_ADC_VC_ADC2_CHANNEL_SEL(adc2_ch);  
> > >
> > > Are you open to either use an errno (maybe EACCES) or define something
> > > custom (maybe RZN1_ADC_NO_CHANNEL) instead of hardcoded -1? I think I
> > > like the latter a tad more.  
> >
> > I prefer RZN1_ADC_NO_CHANNEL too instead of an error code and I will use
> > that instead of -1 in the next iteration.  
> 
> Or just -ENODEV or -ENOENT, and change the checks above to
> "if (adc1_ch >= 0)"?

I prefer to avoid mixing channel numbers with error code.

The specific RZN1_ADC_NO_CHANNEL value looks good to me meaning "No channel
to use".

Best regards,
Hervé