Message-ID: <509FFF8B.3010707@gmail.com>
Date: Sun, 11 Nov 2012 13:42:03 -0600
From: Rob Herring <robherring2@gmail.com>
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To: Viresh Kumar <viresh.kumar@linaro.org>
CC: rob.herring@calxeda.com, grant.likely@secretlab.ca,
        linaro-dev@lists.linaro.org, andriy.shevchenko@intel.com,
        patches@linaro.org, devicetree-discuss@lists.ozlabs.org,
        spear-devel@list.st.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH Resend V2] dt: add helper function to read u8 & u16 variables
 & arrays
References: <64c5278ebdec503f83e9b7002bf13affb7f3260f.1351225085.git.viresh.kumar@linaro.org> <50991C41.50705@gmail.com> <CAOh2x==LNuSFftB1r8cyJ6TOqOVJfExMTUVxKZnS16wL4B8eBA@mail.gmail.com> <509FB25F.3030307@gmail.com> <CAKohpoksQ4ShO_QFAQORO2_oEgNtOeENFnX1C3gN_5POQSGexg@mail.gmail.com>
In-Reply-To: <CAKohpoksQ4ShO_QFAQORO2_oEgNtOeENFnX1C3gN_5POQSGexg@mail.gmail.com>
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On 11/11/2012 11:27 AM, Viresh Kumar wrote:
> On 11 November 2012 19:42, Rob Herring <robherring2@gmail.com> wrote:
>> On 11/06/2012 10:22 PM, viresh kumar wrote:
> 
>>>                 cluster0: cluster@0 {
>>> +                       data1 = <0x50 0x60 0x70>;
>>> +                       data2 = <0x5000 0x6000 0x7000>;
>>> +                       data3 = <0x50000000 0x60000000 0x70000000>;
>>
>> So there is a mismatch in our assumptions. You are just truncating
>> 32-bit values. I assumed you were using the 8 and 16 bit sizes that are
>> now supported in dts. I don't think we should just truncate values
>> blindly. We have support for specifying 8 and 16 values now so you
>> should use that and define that as part of a binding.
> 
> Sorry couldn't get your point at all :(
> What did you mean by "truncating 32 bit values" and how should we
> tell via DT, that the value passed is 8 bit, 16 bit or 32 bit?
> 

You are trying to retrieve an array of 8 or 16-bit values which are
stored as 32-bit values in dtb. Why not define them in the binding as 8
or 16 bit to begin with. Then there is never any ambiguity about their size.

I don't think the size is stored in the dtb. It is only in the dts. You
need to define the size in the binding definitions and use '/bits/'
annotation. With this the data is packed. Then the array function used
should match what the binding defines.

Rob

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