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Date: Tue, 11 Nov 2014 13:29:44 -0300
From: Ezequiel Garcia <ezequiel.garcia@imgtec.com>
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To: Andrew Bresticker <abrestic@chromium.org>
CC: Jonathan Cameron <jic23@kernel.org>, Lars-Peter Clausen <lars@metafoo.de>,
	James Hartley <james.hartley@imgtec.com>, Phani Movva
	<phani.movva@imgtec.com>, <linux-iio@vger.kernel.org>, <pmeerw@pmeerw.net>,
	<knaack.h@gmx.de>, "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	Naidu Tellapati <Naidu.Tellapati@imgtec.com>, Rob Herring
	<robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>, Mark Rutland
	<mark.rutland@arm.com>, Ian Campbell <ijc+devicetree@hellion.org.uk>, "Kumar
 Gala" <galak@codeaurora.org>
Subject: Re: [PATCH v2 2/3] DT: iio: adc: Add CC_10001 binding documentation
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On 11/10/2014 06:28 PM, Andrew Bresticker wrote:
> Ezequiel,
> 
> On Mon, Nov 10, 2014 at 11:59 AM, Ezequiel Garcia
> <ezequiel.garcia@imgtec.com> wrote:
>> On 11/10/2014 04:50 PM, Ezequiel Garcia wrote:
>>> On 11/08/2014 09:57 AM, Jonathan Cameron wrote:
>>>> On 05/11/14 21:56, Ezequiel Garcia wrote:
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/iio/adc/cc_10001_adc.txt b/Documentation/devicetree/bindings/iio/adc/cc_10001_adc.txt
>>>>> new file mode 100644
>>>>> index 0000000..6491839
>>>>> --- /dev/null
>>>>> +++ b/Documentation/devicetree/bindings/iio/adc/cc_10001_adc.txt
>>>>> @@ -0,0 +1,19 @@
>>>>> +* Cosmic Circuits - Analog to Digital Converter (CC-10001-ADC)
>>>>> +
>>>>> +Required properties:
>>>>> +  - compatible: Should be "cosmic,10001-adc"
>>>>> +  - reg: Should contain adc registers location and length.
>>>>> +  - cosmic,adc-available-channels: Bitmask of the channels currently enabled.
>>>> I suspect there may be other preferred ways of doing this (child nodes perhaps
>>>> for each enabled channel?)
>>>
>>> Hm, I'm not sure about this. As far I can recall, if a node has children
>>> then it *must* be a bus, which is not the case. Of course, you'll find
>>> examples doing this wrong.
>>>
>>
>> On a second thought... I guess you meant something like this?
>>
>> adc: adc@18101600 {
>>         compatible = "cosmic,10001-adc";
>>         reg = <0x18101600 0x24>;
>>         clocks = <&adc_clk>;
>>         clock-names = "adc";
>>         vref-supply = <&reg_1v8>;
>>         cosmic,channels {
>>                 #address-cells = <1>;
>>                 #size-cells = <0>;
>>                 channel@0 {
>>                         reg = <0>;
>>                 };
>>                 channel@1 {
>>                         reg = <1>;
>>                 };
>>         };
>> };
>>
>> Might be better, but I don't have a strong opinion on it.
> 
> I actually don't think this is any better.  The point of the property
> is to indicate which channels are available for use by the main CPU,
> i.e. channels not used by the RPU co-processor.  The property is not
> used to indicate the presence of certain channels in hardware, in
> which case maybe a bus would be appropriate.
> 
> Also, perhaps it would be better to reverse the sense of the property
> (maybe, "cosmic,reserved-adc-channels") and make it optional?  I did
> something similar for the MIPS GIC binding:
> http://patchwork.linux-mips.org/patch/8268/.
> 

I'm fine with that. If Jonathan agrees with it (or better, if we can
have an ack from a devicetree binding maintainer) I can spin a v3.

Thanks!
-- 
Ezequiel