From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [PATCH 1/2] i2c-core: Add gpio based bus arbitration implementation Date: Fri, 14 Dec 2012 09:06:49 -0700 Message-ID: <50CB4E99.9060506@wwwdotorg.org> References: <1355464254-12768-1-git-send-email-ch.naveen@samsung.com> <1355464254-12768-2-git-send-email-ch.naveen@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1355464254-12768-2-git-send-email-ch.naveen@samsung.com> Sender: linux-samsung-soc-owner@vger.kernel.org To: Naveen Krishna Chatradhi Cc: linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org, grundler@chromium.org, devicetree-discuss@lists.ozlabs.org, broonie@opensource.wolfsonmicro.com, w.sang@pengutronix.de, ben-linux@fluff.org, khali@linux-fr.org, naveen@chromium.org List-Id: linux-i2c@vger.kernel.org On 12/13/2012 10:50 PM, Naveen Krishna Chatradhi wrote: > The arbitrator is a general purpose function which uses two GPIOs to > communicate with another device to claim/release a bus. > diff --git a/Documentation/devicetree/bindings/i2c/arbitrator-i2c.txt b/Documentation/devicetree/bindings/i2c/arbitrator-i2c.txt > new file mode 100644 > index 0000000..cb91ea8 > --- /dev/null > +++ b/Documentation/devicetree/bindings/i2c/arbitrator-i2c.txt > @@ -0,0 +1,56 @@ > +Device-Tree bindings for i2c gpio based bus arbitrator > + > +bus-arbitration-gpios : > + Two GPIOs to use with the GPIO-based bus arbitration protocol > +(see below). > +The first should be an output, and is used to claim the I2C bus, > +the second should be an input, and signals that the other side (Client) > +wants to claim the bus. This allows two masters to share the same I2C bus. I'm confused why this is even needed; the I2C protocol itself defines how multi-master is supposed to work, just using the regular SCL/SDA lines.