Re: [PATCH 07/12] dt-bindings: i2c: Add support for 'i2c-bus' subnode

From: Jon Hunter <jonathanh@nvidia.com>
To: Peter Rosin <peda@axentia.se>,
	Thierry Reding <thierry.reding@gmail.com>,
	David Airlie <airlied@linux.ie>,
	Stephen Warren <swarren@wwwdotorg.org>,
	Alexandre Courbot <gnurou@gmail.com>,
	Wolfram Sang <wsa@the-dreams.de>,
	Linus Walleij <linus.walleij@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>
Cc: linux-tegra@vger.kernel.org, linux-gpio@vger.kernel.org,
	linux-i2c@vger.kernel.org, dri-devel@lists.freedesktop.org,
	devicetree@vger.kernel.org
Subject: Re: [PATCH 07/12] dt-bindings: i2c: Add support for 'i2c-bus' subnode
Date: Tue, 28 Jun 2016 09:21:05 +0100	[thread overview]
Message-ID: <57723371.4060806@nvidia.com> (raw)
In-Reply-To: <0e9ab029-ed95-c3cb-61f5-6acd9da12a24@axentia.se>

On 27/06/16 13:04, Peter Rosin wrote:
> On 2016-06-23 17:59, 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@nvidia.com>
>> Acked-by: Thierry Reding <treding@nvidia.com>
>> ---
>>  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..71bea55d4c1b 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. If the 'i2c-bus'
>> +	subnode is present, only subnodes of this will be considered as I2C
>> +	slaves. The properties, '#address-cells' and '#size-cells' must be
>> +	defined under this subnode if present.
> 
> Hmmm, those #-properties are listed above, under "Required properties", which
> is no longer 100% true. Maybe rephrase to
> 
> 	slaves. The required properties '#address-cells' and '#size-cells'
> 	must be	defined under this subnode instead, if this subnode is present.
> 
> to make the rules (even) clearer?

I see what you are saying but I wonder if the following is better ...

 slaves. The required properties '#address-cells' and '#size-cells'
 must be defined under this subnode if present and not the parent node.

Cheers
Jon

-- 
nvpublic
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