linux-kernel - Re: [PATCH] dt: add helper function to read u8 & u16 variables & arrays

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Message-ID: <CAKohpom5QmO5vbREsMgi4EefLpBxXsk=QWVaZwTwC_Knf72GVA@mail.gmail.com>
Date:	Thu, 25 Oct 2012 19:48:09 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Rob Herring <robherring2@...il.com>
Cc:	grant.likely@...retlab.ca, spear-devel@...t.st.com,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	andriy.shevchenko@...el.com
Subject: Re: [PATCH] dt: add helper function to read u8 & u16 variables & arrays

On 25 October 2012 18:49, Rob Herring <robherring2@...il.com> wrote:
> For some reason, this does not show up on the list either in my mail or
> mail list archives, but it is in patchwork. Can you resend it please.

Strange. I kept you in --to field. I know people added in cc are
sometimes removed
by the list when they have selected "avoid duplicate mails" option for
their list.

> The main question I have is be32_to_cpup() the right thing to do. I
> would expect byte arrays to not need endian conversion, but I haven't
> looked at how '/bits/ x' data is stored.

The problem i see here is:

The data passed via DT comes as Little Endian in the kernel.

For a little endian system, byte zero will contain the data and so
(u8) val

look to be the correct thing.

For a big endian system, byte 3 will contain data as it is swapped by
be32_to_cpup.
So (u8) val would return value stored by byte 0 instead. ??

Does my logic look correct to you??

--
viresh
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