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

Hi,

On Sat, Dec 15, 2012 at 11:21:36PM +0900, Mark Brown wrote:

On Fri, Dec 14, 2012 at 09:06:49AM -0700, Stephen Warren wrote:

quoted

On 12/13/2012 10:50 PM, Naveen Krishna Chatradhi wrote:

quoted

quoted

+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.

quoted

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.

Practically speaking essentially no systems actually do that - mostly
Linux will treat failure to get the bus as an error for example.

It is true that Linux currently does not have proper multi-master
support. It is worth a look what is missing and how far we can get with
the I2C specified arbitration IMO.

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?

That being said. Grant's design was the most promising one.

Thanks,

   Wolfram

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