linux-kernel - Re: [PATCH 1/2] i2c-core: Add gpio based bus arbitration implementation

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Date:	Thu, 24 Jan 2013 19:18:47 +0800
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Wolfram Sang <w.sang@...gutronix.de>
Cc:	Stephen Warren <swarren@...dotorg.org>,
	Naveen Krishna Chatradhi <ch.naveen@...sung.com>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org, grundler@...omium.org,
	devicetree-discuss@...ts.ozlabs.org, ben-linux@...ff.org,
	khali@...ux-fr.org, naveen@...omium.org
Subject: Re: [PATCH 1/2] i2c-core: Add gpio based bus arbitration
 implementation

On Thu, Jan 24, 2013 at 12:13:29PM +0100, Wolfram Sang wrote:
> On Sat, Dec 15, 2012 at 11:21:36PM +0900, Mark Brown wrote:

> > also get things like read operations which appear as multiple
> > transactions on the I2C bus so require something higher level than what
> > multi-master provides.

> I don't get what you mean here. Can you elaborate?

A read is typically implemented as a write of the register address
followed by a read of the value, usually with the ability to free the
bus in between.  If two devices attempt to access the register map
simultaneously this results in the address going wrong.

Download attachment "signature.asc" of type "application/pgp-signature" (837 bytes)