linux-kernel - Re: [PATCH 2/2] iio: adc: ad717x: add AD717X driver

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Date:   Tue, 29 Aug 2023 14:38:03 -0400
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Andy Shevchenko" <andriy.shevchenko@...ux.intel.com>,
        Nuno Sá <noname.nuno@...il.com>,
        "Linus Walleij" <linus.walleij@...aro.org>,
        "Bartosz Golaszewski" <brgl@...ev.pl>
Cc:     "Dumitru Ceclan" <mitrutzceclan@...il.com>,
        "Lars-Peter Clausen" <lars@...afoo.de>,
        "Michael Hennerich" <Michael.Hennerich@...log.com>,
        "Jonathan Cameron" <jic23@...nel.org>,
        "Rob Herring" <robh+dt@...nel.org>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>,
        "Conor Dooley" <conor+dt@...nel.org>,
        "Cosmin Tanislav" <demonsingur@...il.com>,
        "Alexander Sverdlin" <alexander.sverdlin@...il.com>,
        "Hugo Villeneuve" <hvilleneuve@...onoff.com>,
        "Okan Sahin" <okan.sahin@...log.com>,
        "Niklas Schnelle" <schnelle@...ux.ibm.com>,
        "ChiYuan Huang" <cy_huang@...htek.com>,
        "Ramona Bolboaca" <ramona.bolboaca@...log.com>,
        "Ibrahim Tilki" <Ibrahim.Tilki@...log.com>,
        "ChiaEn Wu" <chiaen_wu@...htek.com>,
        "William Breathitt Gray" <william.gray@...aro.org>,
        "Lee Jones" <lee@...nel.org>, "Haibo Chen" <haibo.chen@....com>,
        "Mike Looijmans" <mike.looijmans@...ic.nl>,
        Leonard Göhrs <l.goehrs@...gutronix.de>,
        "Ceclan Dumitru" <dumitru.ceclan@...log.com>,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] iio: adc: ad717x: add AD717X driver

On Tue, Aug 29, 2023, at 09:31, Andy Shevchenko wrote:
> On Tue, Aug 29, 2023 at 11:14:31AM +0200, Nuno Sá wrote:
>> On Thu, 2023-08-10 at 18:36 +0300, Andy Shevchenko wrote:
>> > On Thu, Aug 10, 2023 at 01:57:02PM +0200, Nuno Sá wrote:
>> > > On Thu, 2023-08-10 at 12:33 +0300, Dumitru Ceclan wrote:
>
>> > > Is ad717x_gpio_cleanup() being used anywhere? Moreover I would maybe just
>> > > get rid of
>> > > the #ifdef wrapper and just select GPIOLIB. How often will it be disabled
>> > > anyways?
>> > 
>> > The agreement is that users are depend on and not selecting GPIOLIB.
>> > Any news in these agreement terms?
>> 
>> Hmm no idea about that. If you say so, it's just one new thing I'm learning :)
>Based outside of the U.S.? Some titles might be unavailable in your current location. Go to amazon.de to see the video catalog available in Germany.
> That's the last I know.
> Cc'ing to GPIOLIB maintainers...

>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.

       Arnd