[RFC PATCH 04/19] powerpc: wii: device tree

[Grant Likely]

On Mon, Nov 23, 2009 at 12:54 PM, Albert Herranz
<albert_herranz at yahoo.es> wrote:
> Grant Likely wrote:
>> On Sun, Nov 22, 2009 at 3:01 PM, Albert Herranz <albert_herranz at yahoo.es> wrote:
>>> +               i2c-video {
>>> +                       #address-cells = <1>;
>>> +                       #size-cells = <0>;
>>> +                       compatible = "virtual,i2c-gpio";
>>
>> There isn't a documented binding for this.  Is there a driver for it?
>>
>
> I have a driver for it. But it isn't yet published.
>
> This is the documentation I wrote so far for the bindings.
> Is there a standard for this?

This looks pretty good to me.  The documentation format isn't strict,
just follow the pattern seen in other bindings.  Make sure you post
new bindings to devicetree-discuss at lists.ozlabs.org for review.  A
couple of comments below.

> Documentation/powerpc/dts-bindings/gpio/i2c.txt
>
> GPIO-based I2C
>
> Required properties:
> - compatible : should be "virtual,i2c-gpio".
> - gpios : should specify GPIOs used for SDA and SCL lines, in that order.
> - sda-is-open-drain : should be non-zero if SDA gpio is open-drain.
> - sda-enforce-dir : should be non-zero if SDA gpio must be configured for
>                    input before reading and for output before writing.
> - scl-is-open-drain : should be non-zero if SCL gpio is open-drain.
> - scl-is-output-only : should be non-zero if SCL is an output gpio only.

Instead of looking for a value in these properties, just make them
empty properties and change behaviour based on whether or not the
property is present.

Why is the scl-is-output-only property needed?

> - udelay : signal toggle delay. SCL frequency is (500 / udelay) kHz

You should follow the lead of
Documentation/powerpc/dts-bindings/fsl/i2c.txt here and specify a
clock-frequency property.

> - timeout : clock stretching timeout in milliseconds.

I don't understand what this property means.

g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.