Re: [RFC PATCH 07/13] dt-bindings: i2c: Add support for 'i2c-bus' subnode

[Jon Hunter <jonathanh@xxxxxxxxxx>]

On 17/06/16 17:45, Thierry Reding wrote:
> * PGP Signed by an unknown key
> 
> On Fri, Jun 17, 2016 at 05:30:54PM +0100, Mark Rutland wrote:
>> On Fri, Jun 17, 2016 at 01:03:41PM +0100, Jon Hunter wrote:
>>> The I2C driver core for boards using device-tree assumes any subnode of
>>> an I2C adapter in the device-tree blob as being a I2C slave device.
>>> Although this makes complete sense, some I2C adapters may have subnodes
>>> which are not I2C slaves but subnodes presenting other features. For
>>> example some Tegra devices have an I2C interface which may share its
>>> pins with other devices and to share these pins subnodes for
>>> representing these pins so they have be shared via the pinctrl framework
>>> are needed.
>>>
>>> To allow I2C adapters to have non-I2C specific subnodes in device-tree
>>> that are not parsed by the I2C driver core by adding support for a
>>> 'i2c-bus' subnode where I2C slaves can be placed. If the 'i2c-bus'
>>> subnode is present then all I2C slaves must be placed under this subnode.
>>>
>>> Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx>
>>> ---
>>>  Documentation/devicetree/bindings/i2c/i2c.txt | 8 ++++++++
>>>  1 file changed, 8 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/i2c/i2c.txt b/Documentation/devicetree/bindings/i2c/i2c.txt
>>> index f31b2ad1552b..ed56b08c7e6e 100644
>>> --- a/Documentation/devicetree/bindings/i2c/i2c.txt
>>> +++ b/Documentation/devicetree/bindings/i2c/i2c.txt
>>> @@ -32,6 +32,14 @@ wants to support one of the below features, it should adapt the bindings below.
>>>  - clock-frequency
>>>  	frequency of bus clock in Hz.
>>>  
>>> +- i2c-bus
>>> +	For I2C adapters that have child nodes that are a mixture of both I2C
>>> +	devices and non-I2C devices (such as a pin controller), the 'i2c-bus'
>>> +	subnode can be used for populating I2C devices to prevent the I2C core
>>> +	from attempting to add any non-i2c nodes as I2C devices. If 'i2c-bus'
>>> +	subnode is present then all I2C slaves must be added under this
>>> +	subnode.
>>
>> The general idea seems sound.
>>
>> It would be good if we could remove the mention of the I2C core,
>> something like:
>>
>>   - i2c-bus
>> 	For I2C adapters that have child nodes that are a mixture of both I2C
>> 	devices and non-I2C devices (such as a pin controller), the 'i2c-bus'
>> 	subnode can be used for populating I2C devices. If an 'i2c-bus'
>> 	subnode is present, only subnodes of this will be considered as
>> 	I2C slaves.
>>
>> How are #address-cells and #size-cells handled in this case? I assume
>> that they should live under the i2c-bus subnode, which should be called
>> out.
> 
> Good catch. Yes, I think the i2c-bus subnode would be the right place
> for #address-cells and #size-cells.

Yes, indeed. Thanks. Will fix.

Cheers
Jon

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