linux-kernel - RE: [PATCH v4 3/5] i2c: designware: Add slave definitions

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Date:   Tue, 13 Dec 2016 10:50:44 +0000
From:   Luis de Oliveira <Luis.Oliveira@...opsys.com>
To:     Rob Herring <robh@...nel.org>,
        Luis de Oliveira <Luis.Oliveira@...opsys.com>
CC:     "wsa@...-dreams.de" <wsa@...-dreams.de>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "jarkko.nikula@...ux.intel.com" <jarkko.nikula@...ux.intel.com>,
        "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>,
        "mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Ramiro.Oliveira@...opsys.com" <Ramiro.Oliveira@...opsys.com>,
        "Joao.Pinto@...opsys.com" <Joao.Pinto@...opsys.com>,
        "CARLOS.PALMINHA@...opsys.com" <CARLOS.PALMINHA@...opsys.com>
Subject: RE: [PATCH v4 3/5] i2c: designware: Add slave definitions

The controller for i2c-designware cannot be slave/master at the same time and it has to be enabled knowing beforehand if we want it to be slave or master by something outside of the controller itself.

I as looking and I see the use of this I2C_OWN_SLAVE_ADDRESS with the "linux,slave-24c02" slave interface  but I am not seeing how it will help me identify a selected i2c-designware block as a "slave" device before instantiation. I'm sorry if I'm not understanding properly.
I use the "linux,slave-24c02" to instantiate the i2c-designware as a slave with an address so I can do write/read operations, it is how I tested it. 

Luis

-----Original Message-----
From: Rob Herring [mailto:robh@...nel.org] 
Sent: Monday, December 12, 2016 23:16
To: Luis de Oliveira <Luis.Oliveira@...opsys.com>
Cc: wsa@...-dreams.de; mark.rutland@....com; jarkko.nikula@...ux.intel.com; andriy.shevchenko@...ux.intel.com; mika.westerberg@...ux.intel.com; linux-i2c@...r.kernel.org; devicetree@...r.kernel.org; linux-kernel@...r.kernel.org; Ramiro.Oliveira@...opsys.com; Joao.Pinto@...opsys.com; CARLOS.PALMINHA@...opsys.com
Subject: Re: [PATCH v4 3/5] i2c: designware: Add slave definitions

On Mon, Dec 12, 2016 at 12:35 PM, Luis de Oliveira <Luis.Oliveira@...opsys.com> wrote:
> Hi all,

Please don't top post.

>
> The slave address could be set by the I2C slave backend so I can't use it to setup the controller.
> A boolean property was my initial approach then Andy and Wolfram Sang suggested the use of compatible strings and later It was suggested to use a property to select mode but I can do it again if it's the best way.
> Can you please tell me where should it be documented?

bindings/i2c/i2c.txt.

Actually, looking at this some more, we already have a way to describe the controller being a slave device with the I2C_OWN_SLAVE_ADDRESS flag in the reg property. We should just need a helper to read reg property of each child and check for the bit set.

Rob