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

From: Luis de Oliveira
Date: Tue Dec 13 2016 - 05:59:56 EST

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.


-----Original Message-----
From: Rob Herring [mailto:robh@xxxxxxxxxx]
Sent: Monday, December 12, 2016 23:16
To: Luis de Oliveira <Luis.Oliveira@xxxxxxxxxxxx>
Cc: wsa@xxxxxxxxxxxxx; mark.rutland@xxxxxxx; jarkko.nikula@xxxxxxxxxxxxxxx; andriy.shevchenko@xxxxxxxxxxxxxxx; mika.westerberg@xxxxxxxxxxxxxxx; linux-i2c@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Ramiro.Oliveira@xxxxxxxxxxxx; Joao.Pinto@xxxxxxxxxxxx; CARLOS.PALMINHA@xxxxxxxxxxxx
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@xxxxxxxxxxxx> 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?


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.