linux-kernel - Re: [RFC 4/4] ARM: shmobile: r8a7790: adapt DTS for I2C slave support

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Date:	Thu, 11 Sep 2014 14:17:16 +0200
From:	Marc Dietrich <marvin24@....de>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	linux-i2c@...r.kernel.org, linux-sh@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Jean Delvare <jdelvare@...e.de>,
	Magnus Damm <magnus.damm@...il.com>,
	Andrey Danin <danindrey@...l.ru>, devicetree@...r.kernel.org,
	Stephen Warren <swarren@...dotorg.org>
Subject: Re: [RFC 4/4] ARM: shmobile: r8a7790: adapt DTS for I2C slave support

cc'ing: devicetree

Am Dienstag, 9. September 2014, 16:54:30 schrieb Wolfram Sang:
> From: Wolfram Sang <wsa+renesas@...g-engineering.com>
> 
> Not for upstream!
> 
> Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
> ---
>  arch/arm/boot/dts/r8a7790-lager.dts | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm/boot/dts/r8a7790-lager.dts
> b/arch/arm/boot/dts/r8a7790-lager.dts index 856b4236b674..12aa2f21e6fa
> 100644
> --- a/arch/arm/boot/dts/r8a7790-lager.dts
> +++ b/arch/arm/boot/dts/r8a7790-lager.dts
> @@ -205,9 +205,9 @@
>  		renesas,function = "msiof1";
>  	};
> 
> -	iic1_pins: iic1 {
> -		renesas,groups = "iic1";
> -		renesas,function = "iic1";
> +	i2c1_pins: i2c1 {
> +		renesas,groups = "i2c1";
> +		renesas,function = "i2c1";
>  	};
> 
>  	iic2_pins: iic2 {
> @@ -356,10 +356,15 @@
>  	status = "ok";
>  };
> 
> -&iic1	{
> +&i2c1	{
>  	status = "ok";
> -	pinctrl-0 = <&iic1_pins>;
> +	pinctrl-0 = <&i2c1_pins>;
>  	pinctrl-names = "default";
> +
> +	eeprom@64 {
> +		compatible = "slave-24c02";

a "real" compatible value should have vendor,device syntax.

> +		reg = <0x64>;

we had some discussions in the past how to represent i2c master devices in 
device tree. The outcome was to use to a special representation to distinguish 
them from slave devices, e.g. something like reg = <0x1 0x64>, where the 0x1 
would mean "master" device (0x0 -> slave). If nothing is added, then it's also 
slave. The adapter address cell would also need to be changed if this 
extension is used.

An alternative would be to use a special property (e.g. slave address), but 
that would encode the same value twice (or even three times).

Marc

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