From mboxrd@z Thu Jan  1 00:00:00 1970
From: swarren@wwwdotorg.org (Stephen Warren)
Date: Thu, 05 Apr 2012 13:23:46 -0600
Subject: Point-to-point bus in device tree
In-Reply-To: <20120405181509.GA28693@codeaurora.org>
References: <20120405181509.GA28693@codeaurora.org>
Message-ID: <4F7DF142.5050601@wwwdotorg.org>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 04/05/2012 12:15 PM, David Brown wrote:
> Some MSM SoCs have a small serial-type "bus" that is used to
> communicate with the PMIC devices.  This interface is always
> point-to-point.  I'm doing a device-tree conversion of the driver that
> Ken Heitke posted last year <https://lkml.org/lkml/2011/2/17/503>.
> 
> A naive conversion to device tree, would result in something like
> this:
> 
> 	qcom,ssbi at 500000 {
> 		compatible = "qcom,ssbi";
> 		reg = <0x500000 0x1000>;
> 		qcom,controller-type = "ssbi";
> 
> 		qcom,pmic8058 at 0 {
> 			reg = <0x0 0x01>;
> 			...
> 		}
> 	}
> 
> There would end up being an extraneous register for the device on the
> other end (there are no addresses), and there would need to be code in
> the ssbi driver to traverse this small tree to find these nodes.

Isn't that extra code simply:

of_platform_populate(pdev->dev.of_node, NULL, NULL, &pdev->dev);

That seems like pretty low overhead.