linux-kernel - Re: [PATCH V2 3/3] ARM: dts: db8500: add node property "regulator-compatible" regulator node

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Message-ID: <4FE18371.2020602@linaro.org>
Date:	Wed, 20 Jun 2012 09:01:53 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Laxman Dewangan <ldewangan@...dia.com>
CC:	Stephen Warren <swarren@...dotorg.org>,
	"broonie@...nsource.wolfsonmicro.com" 
	<broonie@...nsource.wolfsonmicro.com>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"arnd@...db.de" <arnd@...db.de>,
	"linus.walleij@...aro.org" <linus.walleij@...aro.org>,
	"lrg@...com" <lrg@...com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 3/3] ARM: dts: db8500: add node property "regulator-compatible"
 regulator node

On 20/06/12 08:39, Laxman Dewangan wrote:
> On Wednesday 20 June 2012 12:39 PM, Lee Jones wrote:
>> On 19/06/12 18:32, Stephen Warren wrote:
>>> On 06/19/2012 10:13 AM, Lee Jones wrote:
>>>>> On 19/06/12 15:28, Laxman Dewangan wrote:
>>>>>>> Device's regulator matches their hardware counterparts with the
>>>>>>> property "regulator-compatible" of each child regulator node in
>>>>>>> place of the child node.
>>>>>>> Add the property "regulator-compatible" for each regulator with
>>>>>>> their name.
>>>>>>>
>>>>>>> Signed-off-by: Laxman Dewangan<ldewangan@...dia.com>
>>>>>>> ---
>>>>>>> Changes from V1:
>>>>>>> - This is new change in V2.
>>>>>>>
>>>>>>> arch/arm/boot/dts/db8500.dtsi | 128
>>>>>>> +++++++++++++++++++++++++++++++----------
>>>>>>> 1 files changed, 97 insertions(+), 31 deletions(-)
>>>>>>>
>>>>>>> diff --git a/arch/arm/boot/dts/db8500.dtsi
>>>>>>> b/arch/arm/boot/dts/db8500.dtsi
>>>>>>> index 4ad5160..9548f80 100644
>>>>>>> --- a/arch/arm/boot/dts/db8500.dtsi
>>>>>>> +++ b/arch/arm/boot/dts/db8500.dtsi
>>>>>>> @@ -203,107 +203,149 @@
>>>>>>>
>>>>>>> db8500-prcmu-regulators {
>>>>>>> compatible = "stericsson,db8500-prcmu-regulator";
>>>>>>> + #address-cells =<1>;
>>>>>>> + #size-cells =<0>;
>>>>> Why are these and the reg properties required?
>>> DT nodes should be named after the type of object they describe (e.g.
>>> "regulator") rather than the name of the object they're describing (e.g.
>>> "vape").
>>>
>>> Once you've made that change, you end up with many nodes with the same
>>> name in the same parent, so you need to make their names unique. You do
>>> this by adding a "unit address" to each of them - "@0", "@1", ... But,
>>> in order to be "allowed" to use such a unit address, you need a reg
>>> property that matches the unit address, and #address-cells/#size-cells
>>> in the parent node.
>> I don't like it. By doing this you are preventing any regulator from
>> being registered by of_platform_populate(). Also, the nodes are already
>> placed under an identifying node "db8500-prcmu-regulators", so we know
>> they are regulators, making the regulator@x, the reg property and the
>> *-cells properties unnecessary cruft.
>>
>> I'd prefer to have the second label removed and just to call the
>> regulators by their correct name. The property names become functionally
>> redundant after the previous patch has been applied in any case.
>>
>> Something like this:
>>
>>> db8500-prcmu-regulators {
>>> compatible = "stericsson,db8500-prcmu-regulator";
>>>
>>> // DB8500_REGULATOR_VAPE
>>> - db8500_vape_reg: db8500_vape {
>>> + db8500_vape {
>>> + regulator-compatible = "db8500_vape";
>>> regulator-name = "db8500-vape";
>>> regulator-always-on;
>>> };
>>
>
>
> You will require a label so that it can refer by the consumer.

Don't they both act as labels? Thus if you removed the second one, the 
phandle will be taken from the remaining label? It's not something I've 
tried, so I'm happy to be wrong here.

If I'm wrong about that, can't we just omit the reg and *-size 
properties? They are meaningless and restrictive.

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
M: +44 77 88 633 515
Linaro.org │ Open source software for ARM SoCs
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