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Re: [PATCH 5/6] RTC: SMBus support for the M41T80, etc. driver (#2)

To: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Subject: Re: [PATCH 5/6] RTC: SMBus support for the M41T80, etc. driver (#2)
From: "Maciej W. Rozycki" <macro@linux-mips.org>
Date: Sat, 17 May 2008 21:46:35 +0100 (BST)
Cc: khali@linux-fr.org, a.zummo@towertech.it, akpm@linux-foundation.org, dwmw2@infradead.org, ralf@linux-mips.org, tglx@linutronix.de, rtc-linux@googlegroups.com, i2c@lm-sensors.org, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org
In-reply-to: <20080518.003157.126143021.anemo@mba.ocn.ne.jp>
Original-recipient: rfc822;linux-mips@linux-mips.org
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On Sun, 18 May 2008, Atsushi Nemoto wrote:

> I suppose the "off by one second" issue is not the matter each driver
> should take care of.  This race is common for most RTC chip.

 I agree, but with the reread it comes for free here.  Given you have two 
values of seconds available here, which one would you choose?  You can't 
take both at once. ;-)

> I do not have strong opinion for optimization suggested by Jean.  It
> might be better, but I'm OK with current your patch.

 Hmm, it looks as simple as putting a clause like:

        if (i2c_check_functionality(client->adapter, 
                                    I2C_FUNC_SMBUS_READ_I2C_BLOCK)
                break;

into the loop and even at 400kHz it saves a considerable amount of time.
It sounds plausible -- I'll do that.

  Maciej

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