linux-kernel - Re: [PATCH v2 2/2] iio: adc: ad7173: add AD7173 driver

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Date:   Tue, 3 Oct 2023 14:02:33 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Ceclan Dumitru-Ioan <mitrutzceclan@...il.com>
Cc:     Andy Shevchenko <andy@...nel.org>,
        Jonathan Cameron <jic23@...nel.org>, linus.walleij@...aro.org,
        brgl@...ev.pl, linux-gpio@...r.kernel.org,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Michael Walle <michael@...le.cc>,
        Arnd Bergmann <arnd@...db.de>,
        ChiaEn Wu <chiaen_wu@...htek.com>,
        Niklas Schnelle <schnelle@...ux.ibm.com>,
        Leonard Göhrs <l.goehrs@...gutronix.de>,
        Mike Looijmans <mike.looijmans@...ic.nl>,
        Haibo Chen <haibo.chen@....com>,
        Hugo Villeneuve <hvilleneuve@...onoff.com>,
        Ceclan Dumitru <dumitru.ceclan@...log.com>,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] iio: adc: ad7173: add AD7173 driver

On Tue, Oct 3, 2023 at 1:57 PM Ceclan Dumitru-Ioan
<mitrutzceclan@...il.com> wrote:
> On 10/3/23 13:45, Andy Shevchenko wrote:
> > On Tue, Oct 03, 2023 at 01:33:36PM +0300, Ceclan Dumitru-Ioan wrote:
> >> On 9/30/23 17:05, Jonathan Cameron wrote:
> >>> On Thu, 28 Sep 2023 15:54:43 +0300
> >>> Dumitru Ceclan <mitrutzceclan@...il.com> wrote>> +config AD7173

...

> >>>> +  select GPIO_REGMAP
> >>> If you are selecting it, why does it have if guards in the driver.
> >>> I prefer the select here, so drop this if guards.
> >> From what i checked, selecting GPIO_REGMAP does not select GPIOLIB but only REGMAP.
> >>
> >> Also, in the thread from V1 Arnd Bergmann suggested:
> >>      " I think the best way to handle these is to remove both
> >>       the 'select' and the #ifdef in the driver and instead use
> >>       'if (IS_ENABLED(CONFIG_GPIOLIB))' to handle optional gpio
> >>       providers in the code. "
> > Why not simply to be dependent on GPIOLIB like other drivers do in this folder?
>
> I followed the suggestion given by Arnd. The full argument:
>
> "From a Kconfig perspective, any user-visible symbol ideally only uses
> 'depends on', while hidden symbols usually use 'select'.
>
> For the GPIOLIB symbol specifically, we have a mix of both, but the
> overall usage is that gpio consumers only use 'depends on',
> while some of the providers use 'select'. This risks causing build
> breakage from a dependency loop when combined with other symbols
> that have the same problem (e.g. I2C), but it tends to work out
> as long as a strong hierarchy is kept. In particular, using 'select'
> from an arch/*/Kconfig platform option is generally harmless as
> long as those don't depend on anything else.
>
> The new driver is a gpio provider and at least ad4130 and
> ad5592r uses 'select' here, but then again ad74115 and
> ad74113 use 'depends on' and ads7950 uses neither.
>
> I think the best way to handle these is to remove both
> the 'select' and the #ifdef in the driver and instead use
> 'if (IS_ENABLED(CONFIG_GPIOLIB))' to handle optional gpio
> providers in the code."
>
> I do not have a lot of experience with this subject.
> As such, if you consider the argument invalid, mention it and i will
> change to 'depends on'.

I see, I would ask GPIOLIB maintainers about this.
I don't know if there is any plan to fix this through the entire
kernel and which way has been chosen for that.


-- 
With Best Regards,
Andy Shevchenko