linux-kernel - Re: [lm-sensors] [PATCH 1/2] hwmon: (adm1031) Replace update_rate sysfs attribute with update

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Date:	Thu, 16 Sep 2010 18:01:12 +0200
From:	Jean Delvare <khali@...ux-fr.org>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	Guenter Roeck <guenter.roeck@...csson.com>,
	Randy Dunlap <rdunlap@...otime.net>, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, lm-sensors@...sensors.org
Subject: Re: [lm-sensors] [PATCH 1/2] hwmon: (adm1031) Replace update_rate 
 sysfs attribute with update_interval

On Thu, 16 Sep 2010 12:42:43 -0300, Henrique de Moraes Holschuh wrote:
> On Thu, 16 Sep 2010, Jean Delvare wrote:
> > On Wed, 15 Sep 2010 19:07:14 -0700, Guenter Roeck wrote:
> > > The attribute reflects an interval, not a rate.
> > > 
> > > Signed-off-by: Guenter Roeck <guenter.roeck@...csson.com>
> > > ---
> > >  Documentation/hwmon/sysfs-interface |   12 +++++-----
> > >  drivers/hwmon/adm1031.c             |   43 +++++++++++++++++++---------------
> > >  2 files changed, 30 insertions(+), 25 deletions(-)
> > > 
> > > diff --git a/Documentation/hwmon/sysfs-interface b/Documentation/hwmon/sysfs-interface
> > > index ff45d1f..df0cdd2 100644
> > > --- a/Documentation/hwmon/sysfs-interface
> > > +++ b/Documentation/hwmon/sysfs-interface
> > > @@ -91,13 +91,13 @@ name		The chip name.
> > >  		I2C devices get this attribute created automatically.
> > >  		RO
> > >  
> > > -update_rate	The rate at which the chip will update readings.
> > > -		Unit: millisecond
> > > +update_interval	The interval at which the chip or driver will update readings.
> > 
> > I think I prefer the original wording. The attribute is really about
> > setting the register refresh rate at the hardware level. The fact that
> 
> Only, it doesn't set any rates in the hardware.  It sets the period
> (interval).
> 
> If the unit of update_rate is changed to Hz, and the driver does
> hardware_timer_milliseconds = 1000/update_rate_Hz, THEN it will be
> correct to call it a rate...

I agree. My point was really only about "chip or driver" vs. "chip".

> I'd rather have it in Hz, actually.  I consider that more user-friendly.
> But that's just personal preference.

The problem with Hz is that we need to be able to handle values lower
than 1, and mHz as a unit isn't exactly friendly. I would be very fine
with Hz (especially as we use it for pwmN_freq already) if we didn't
have to support frequencies below 1 Hz. For such low frequencies,
period (or interval) is clearer than frequency IMHO.

-- 
Jean Delvare
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