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

From: Peter Rosin <peda@axentia.se>
To: Jon Hunter <jonathanh@nvidia.com>,
	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: dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org,
	linux-i2c@vger.kernel.org, linux-gpio@vger.kernel.org,
	devicetree@vger.kernel.org
Subject: Re: [PATCH 07/12] dt-bindings: i2c: Add support for 'i2c-bus' subnode
Date: Mon, 27 Jun 2016 14:04:09 +0200	[thread overview]
Message-ID: <0e9ab029-ed95-c3cb-61f5-6acd9da12a24@axentia.se> (raw)
In-Reply-To: <1466697545-11868-8-git-send-email-jonathanh@nvidia.com>

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?

Cheers,
Peter

> +
>  - i2c-scl-falling-time-ns
>  	Number of nanoseconds the SCL signal takes to fall; t(f) in the I2C
>  	specification.
> 