linux-kernel - Re: [PATCH v2 1/3] units: complement the set of Hz units

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Message-ID: <20220731124140.777ddd05@jic23-huawei>
Date:   Sun, 31 Jul 2022 12:41:55 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Dmitry Rokosov <DDRokosov@...rdevices.ru>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        "wsa@...nel.org" <wsa@...nel.org>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "Michael.Hennerich@...log.com" <Michael.Hennerich@...log.com>,
        "jbhayana@...gle.com" <jbhayana@...gle.com>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        kernel <kernel@...rdevices.ru>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] units: complement the set of Hz units

On Fri, 29 Jul 2022 20:02:42 +0200
Andy Shevchenko <andy.shevchenko@...il.com> wrote:

> On Fri, Jul 29, 2022 at 7:23 PM Dmitry Rokosov <DDRokosov@...rdevices.ru> wrote:
> >
> > Currently, Hz units do not have milli, micro and nano Hz coefficients.
> > Some drivers (IIO especially) use their analogues to calculate
> > appropriate Hz values. This patch includes them to units.h definitions,
> > so they can be used from different kernel places.  
> 
> ...
> 
> > +#define NHZ_PER_HZ             1000000000UL
> > +#define UHZ_PER_HZ             1000000UL
> > +#define MILLIHZ_PER_HZ         1000UL  
> 
> Oh, but then a bit of consistency?
> 
> MICRO
> NANO
Tricky given existing items, but I agree we shouldn't make
it worse.

However, I'm not 100% sold on why we need these conversions relative to HZ.
What's wrong with using MILLI / NANO etc as already defined?  I guess
there is a 'documentation' like effect of making it clear these are frequency
unit conversions, but I don't think it makes sense to add it for all the other
types of unit, so why is Hz special?

I'm not sure why we have the existing ones for HZ with the
exception of KHZ_PER_MEGAHZ.

Jonathan

>