From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jean Delvare Subject: Re: Driver for pca9541 bus master selector Date: Tue, 28 Sep 2010 18:42:15 +0200 Message-ID: <20100928184215.00f82717@endymion.delvare> References: <20100928143302.GA7593@ericsson.com> <20100928171607.395f7736@endymion.delvare> <20100928160746.GB7976@ericsson.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20100928160746.GB7976-IzeFyvvaP7pWk0Htik3J/w@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Guenter Roeck Cc: "linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Michael Lawnick , Rodolfo Giometti List-Id: linux-i2c@vger.kernel.org On Tue, 28 Sep 2010 09:07:46 -0700, Guenter Roeck wrote: > On Tue, Sep 28, 2010 at 11:16:07AM -0400, Jean Delvare wrote: > > Hi Guenter, > > > > On Tue, 28 Sep 2010 07:33:02 -0700, Guenter Roeck wrote: > > > I am in the process of writing a driver for the pca9541 bus master selector. > > > I using the i2c multiplexer framework, which fits the requirements quite nicely. > > > > > > If anyone happens to know about an existing driver for this chip, please let me know. > > > I would love to get some input for the arbitration mechanism needed to determine > > > if and when to switch bus ownership from one master to the other. > > > > See drivers/i2c/muxes/pca954x.c in 2.6.36-rc2 and later. > > > Yes, I know. I use it as basis. But it doesn't support pca9541, unfortunately. Oh, my bad. I had not noticed the PCA9541 was of a totally different kind. > I use the select/deselect mechanism to trigger arbitration, but I still need > a mechanism to communicate between the masters. After all, the problem to solve > is that I have two masters and one slave, not one master and multiple slaves > as with the other chips. > > Note that I do have a solution which I think will work. Just figured it might > save time if someone else already solved the same problem, and especially it > might help me to determine arbitration time constants. There was mention of > a pca9541 driver several years ago, but I have not been able to find details. -- Jean Delvare