linux-kernel - Re: [PATCH v3 6/6] iio: adc: Add support for AD4000

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Date: Tue, 11 Jun 2024 18:05:59 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
CC: Jonathan Cameron <jic23@...nel.org>, Nuno Sá
	<noname.nuno@...il.com>, Marcelo Schmitt <marcelo.schmitt@...log.com>,
	<broonie@...nel.org>, <lars@...afoo.de>, <Michael.Hennerich@...log.com>,
	<robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
	<conor+dt@...nel.org>, <nuno.sa@...log.com>, <dlechner@...libre.com>,
	<marcelo.schmitt1@...il.com>, <linux-iio@...r.kernel.org>,
	<devicetree@...r.kernel.org>, <linux-spi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>
Subject: Re: [PATCH v3 6/6] iio: adc: Add support for AD4000

On Tue, 11 Jun 2024 13:34:29 +0300
Andy Shevchenko <andy.shevchenko@...il.com> wrote:

> Sun, Jun 09, 2024 at 10:23:54AM +0100, Jonathan Cameron kirjoitti:
> 
> ...
> 
> > > > +	/*
> > > > +	 * In 4-wire mode, the CNV line is held high for the entire
> > > > conversion
> > > > +	 * and acquisition process. In other modes st->cnv_gpio is NULL and
> > > > is
> > > > +	 * ignored (CS is wired to CNV in those cases).
> > > > +	 */
> > > > +	gpiod_set_value_cansleep(st->cnv_gpio, 1);    
> > > 
> > > Not sure it's a good practise to assume internal details as you're going for
> > > GPIO. I would prefer to have an explicit check for st->cnv_gpio being NULL or
> > > not.  
> > 
> > Hmm. I had it in my head that this was documented behaviour, but
> > I can't find such in the docs, so agreed checking it makes sense.
> > 
> > I would be very surprised if this ever changed as it's one of the
> > things that makes optional gpios easy to work with but who knows!  
> 
> Not Linus and not Bart, but we have tons of drivers that call GPIO APIs
> unconditionally as long as they want optional GPIO.
> 
> What I see here is the comment that should be rewritten to say something like
> 
> "if GPIO is defined blablabla, otherwise blablabla."
> 
> I.o.w. do not mention that implementation detail (being NULL, i.e. optional).
> 

Good point - handy comment there already and this minor tweak will make it clear.

Thanks Andy!

Jonathan