linux-kernel - Re: [RFC+PATCH] RTC calibration

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Message-ID: <46E6B617.7030106@anagramm.de>
Date:	Tue, 11 Sep 2007 17:36:55 +0200
From:	Clemens Koller <clemens.koller@...gramm.de>
To:	Dag-Erling Smørgrav <des@...pro.no>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [RFC+PATCH] RTC calibration

Dag-Erling Smørgrav schrieb:
 > Clemens Koller <clemens.koller@...gramm.de> writes:
 >> It looks odd to me to do only differential up and down adjustments.
 >> I would prefer read_calibration_register and write_calibration_register
 >> access and let the userspace decide how much it wants to
 >> increment/decrement the register.
 >
 > Without knowing exacly which chip is present, there is no way for the
 > userland calibration tool to know how big a difference a calibration
 > step makes.

I am not talking about the calibration algorithm and it's quality.
I am talking about _how_ the calibration register is addressed from
userspace. It's a simple register, some bits at address 7 and I would
expect to read/modify/write registers to do all the things you want
to do. Register access in userspace doesn't put any limitation
to applications.
Having only incs and decs without getting the actual value back seems
to be an absolutely unnecessary limitation here.
You cannot get the current value back to see if it's i.e. in saturation in
a way that it doesn't make sense to inc/decrement it further or in bigger steps
or reset it to zero...

Regards,

Clemens Koller
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