linux-kernel - Re: [RFC PATCH] pinctrl-single: Use of pinctrl-single for external device over I2C

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Date:	Thu, 16 Jul 2015 19:46:03 +0530
From:	Vaibhav Hiremath <vaibhav.hiremath@...aro.org>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Rob Herring <robh+dt@...nel.org>,
	Lee Jones <lee.jones@...aro.org>,
	Will Deacon <will.deacon@....com>,
	Tony Lindgren <tony@...mide.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>
Subject: Re: [RFC PATCH] pinctrl-single: Use of pinctrl-single for external
 device over I2C



On Thursday 16 July 2015 06:28 PM, Linus Walleij wrote:
> On Thu, Jul 2, 2015 at 6:53 PM, Vaibhav Hiremath
> <vaibhav.hiremath@...aro.org> wrote:
>
>> In some usecases, the external device (in my case it PMIC over I2C)
>> does support pin in multiple configuration, we may need to control/configure them
>> during boot or runtime.
>
> What is missing from this patch is an explanation why pinctrl-single should
> be used for this PMIC.
>
> Repeat: pinctrl-single: when you have exactly one register per pin, and
> the description of the pins is delivered in an opaque ASIC-specific format
> without developers knowing much about how the hardware actually works,
> just "set these magic values".
>
> I strongly prefer that this PMIC has its own pin controller using standard
> bindings with groups and functions, see eg. drivers/pinctrl/nomadik/pinctrl-ab*
> for a PMIC pinctrl driver.
>

Thanks for the reference, good to know this.
Let me check this driver before commenting anything further on this.

Thanks,
Vaibhav

> Yours,
> Linus Walleij
>
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