linux-kernel - Re: [PATCH] rtc-ds1307: True SMBus compatibility

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Message-ID: <9ae48b020901070722l77bebc6boc8fa2fd0bcc8da28@mail.gmail.com>
Date:	Wed, 7 Jan 2009 07:22:12 -0800
From:	"Ed Swierk" <eswierk@...stanetworks.com>
To:	"Jean Delvare" <khali@...ux-fr.org>
Cc:	linux-i2c@...r.kernel.org, "David Brownell" <david-b@...bell.net>,
	"Alessandro Zummo" <a.zummo@...ertech.it>,
	linux-kernel@...r.kernel.org,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"BARRE Sebastien" <sbarre@...lcc.com>
Subject: Re: [PATCH] rtc-ds1307: True SMBus compatibility

On Wed, Jan 7, 2009 at 5:24 AM, Jean Delvare <khali@...ux-fr.org> wrote:
> Are you certain the nForce2 controllers can't do it? The i2c-nforce2
> driver doesn't implement it, but this doesn't mean the hardware can't
> do it. I don't have any datasheet for these chips, but I know their
> SMBus implementation is very similar to those of the AMD 8111, and
> i2c-amd8111 has support for I2C block reads and writes. I think it
> would be worth giving it a try, by copying the i2c-amd8111
> implementation into the i2c-nforce2 driver and seeing if it happens to
> just work. If it works, that would be more elegant than your proposed
> hack to the rtc-ds1307 driver.

I checked the datasheet and also tried every possible SMBus command
value to try to discover any supported commands that the i2c-nforce2
driver happens not to use, to no avail. The nVidia SMBus is pure
SMBus.

I could change the ds1307 driver to check whether the controller
supports i2c block commands and fall back to emulation only if they
are not available. Would that address your concerns?

--Ed
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