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

From: Rob Herring
Date: Tue Dec 13 2016 - 09:12:23 EST

Again, please don't top post. And your line wrapping is messed up.
IOW, you can't use Outlook.

On Tue, Dec 13, 2016 at 4:50 AM, Luis de Oliveira
<Luis.Oliveira@xxxxxxxxxxxx> wrote:
> 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.

Something like this:

of_for_each_child_node(child) {
of_property_read_u32(child, "reg", &reg);
im_a_slave = true;

...rather than testing "mode" is equal to "slave".


> Luis
> -----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?
> 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