Re: [PATCH 1/2] i2c: tegra: Maintain CPU endianness

[Dmitry Osipenko]

22.01.2015 19:06, Dmitry Osipenko ÐÐÑÐÑ:
> 22.01.2015 18:22, Dmitry Osipenko ÐÐÑÐÑ:
> > 22.01.2015 10:55, Alexandre Courbot ÐÐÑÐÑ:
> > > On Thu, Jan 22, 2015 at 4:40 PM, Thierry Reding
> > > <thierry.reding@xxxxxxxxx> wrote:
> > > > Should this not technically be le32_to_cpu() since the data originates
> > > > from the I2C controller?
> >
> > No, i2c_readl returns value in CPU endianness, so it's correct. But for
> > i2c_writel should be used le32_to_cpu(), since it takes value in CPU endianness.
> > It's my overlook, V2 is coming.
> >
> > > > Why does this have to be initialized to 0 now?
> > >
> > > I suspect this is because we are going to memcpy less than 4 bytes
> > > into it, but I cannot figure out how that memcpy if guaranteed to
> > > produce the expected result for both endiannesses.
> > That's correct. Memcpy is working with bytes, so it doesn't care about
> > endianness and produces expected result, since I2C message is char array.
> I'll spend some more time reviewing, to see if nullifying should go as separate
> patch.
Well, I2C_FIFO_STATUS returns 8-bit value. The rest of bits very likely to be 
RAZ, however I don't see anything on it in documentation. In that case it won't 
cause any problems with LE value and nullifying is only needed for BE mode.

--
Dmitry
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