linux-kernel - Re: [PATCH v3 1/3] nvmem: Update the OF binding to use a subnode for the cells list

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Date:   Wed, 18 Apr 2018 13:41:19 +0200
From:   Alban <albeu@...e.fr>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     Alban <albeu@...e.fr>, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        devicetree@...r.kernel.org, linux-mtd@...ts.infradead.org
Subject: Re: [PATCH v3 1/3] nvmem: Update the OF binding to use a subnode
 for the cells list

On Tue, 17 Apr 2018 18:00:40 +0200
Alban <albeu@...e.fr> wrote:

> On Tue, 17 Apr 2018 16:44:01 +0100
> Srinivas Kandagatla <srinivas.kandagatla@...aro.org> wrote:
> 
> > Thanks for explaining,
> > 
> > On 17/04/18 15:54, Alban wrote:  
> > > This will not only allow reading the calibration data from nvmem, but
> > > will also create a partition on the MTD device, which is not acceptable.
> > > With my proposed binding this would become:
> > > 
> > > flash@0 {
> > > 	#address-cells = <1>;
> > > 	#size-cells = <1>;
> > > 	compatible = "s25sl064a";
> > > 	reg = <0>;
> > > 
> > > 	nvmem-cells {
> > > 		compatible = "nvmem-cells";
> > > 		#address-cells = <1>;
> > > 		#address-cells = <1>;
> > > 
> > > 		calibration: calib@404 {
> > > 			reg = <0x404 0x10>;
> > > 		};
> > > 	};    
> > 
> > Why can't we make nvmem-cells node a nvmem provider in this case?
> > Which should work!  
> 
> TBH I just copied what have been done to fix the same problem with the
> MTD partitions. But yes we could also just extend the current binding
> to require a compatible string on each nvmem-cell, which would not
> require any code change to support.

However this scheme will not work if the device node binding already
have subnodes with addresses. The addressing, as specified by
#address-cells and #size-cells, might be incompatible or might overlap.
Using the nvmem-cells subnode solve this problem.

Alban


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