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Date: Fri, 20 Oct 2023 16:31:50 +0200
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: "Balas, Eliza" <Eliza.Balas@analog.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Derek Kiernan <derek.kiernan@amd.com>,
	Dragan Cvetic <dragan.cvetic@amd.com>,
	Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v3 2/2] drivers: misc: adi-axi-tdd: Add TDD engine
Message-ID: <2023102030-resort-glance-57ef@gregkh>
References: <20231019125646.14236-1-eliza.balas@analog.com>
 <20231019125646.14236-3-eliza.balas@analog.com>
 <2023101917-cork-numeric-dab8@gregkh>
 <BN7PR03MB4545E7EAB2D72B9098C30C6797DBA@BN7PR03MB4545.namprd03.prod.outlook.com>
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On Fri, Oct 20, 2023 at 11:18:44AM +0000, Balas, Eliza wrote:
> > > +static int adi_axi_tdd_parse_ms(struct adi_axi_tdd_state *st,
> > > +				const char *buf,
> > > +				u64 *res)
> > > +{
> > > +	u64 clk_rate = READ_ONCE(st->clk.rate);
> > > +	char *orig_str, *modf_str, *int_part, frac_part[7];
> > > +	long ival, frac;
> > > +	int ret;
> > > +
> > > +	orig_str = kstrdup(buf, GFP_KERNEL);
> > > +	int_part = strsep(&orig_str, ".");
> > 
> > Why are we parsing floating point in the kernel?  Please just keep the
> > api simple so that we don't have to try to do any type of parsing other
> > than turning a single text number into a value.
> > 
> 
> The adi_axi_tdd_parse_ms function does almost the same thing as the 
> iio_str_to_fixpoint() function which already exists in kernel.

That does not mean that this is a valid api for your device as you are
not an iio driver (why aren't you an iio driver?)

> It parses a fixed-point number from a string. 

And as such, you shouldn't duplicate existing logic.

> The __iio_str_to_fixpoint is used in a similar way, as I intend to use adi_axi_tdd_parse_ms.
> It writes to a channel the corresponding scale (micro,nano) for a value.

Why not just have the api accept values in nanoseconds and then no
parsing is needed?

> Since the device is not an iio device, using an iio function would be confusing.

Why isn't this an iio device?

thanks,

greg k-h