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

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Message-ID: <CAPnjgZ30MQS1OT3GOFLG9HntoD8NrzNw6bB_d1fiJEgHcMDGUA@mail.gmail.com>
Date:	Wed, 19 Dec 2012 16:17:03 -0800
From:	Simon Glass <sjg@...omium.org>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	Grant Likely <grant.likely@...retlab.ca>,
	Naveen Krishna Chatradhi <ch.naveen@...sung.com>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	lk <linux-kernel@...r.kernel.org>,
	linux-samsung-soc@...r.kernel.org,
	Wolfram Sang <w.sang@...gutronix.de>, khali@...ux-fr.org,
	Ben Dooks <ben-linux@...ff.org>,
	Devicetree Discuss <devicetree-discuss@...ts.ozlabs.org>,
	Grant Grundler <grundler@...omium.org>,
	Naveen Krishna <naveen@...omium.org>
Subject: Re: [PATCH 1/2] i2c-core: Add gpio based bus arbitration implementation

On Wed, Dec 19, 2012 at 9:14 AM, Mark Brown
<broonie@...nsource.wolfsonmicro.com> wrote:
> On Wed, Dec 19, 2012 at 12:32:01PM +0000, Grant Likely wrote:
>
>> I'm not convinced on the design of this protocol. It won't scale beyond
>> 2 bus masters and it seems very specific to the design of a specific
>> piece of hardware. I don't think it is mature enough to bake into the
>
> I ought to point out that the original patch would've baked this into
> the Samsung I2C driver but I asked for it to be split out as it's
> nothing to do with the controller really and I'm sure I've seen it
> before.

Grant your idea looks nice to me. I only worry if we should wait until
we have a second user before going so far with it. But it is certainly
a nice general solution.

The scaling beyond two bus masters would require the code to be
changed to check more input lines from other masters. Best avoided for
now I think until we have a use for it.

Regards,
Simon
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