Re: [PATCH 0/4] lis3lv02d: update DT binding for use with Nokia N900

[Sebastian Reichel <sre-8fiUuRrzOP0dnm+yROfE0A@public.gmane.org>]

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On Fri, Dec 13, 2013 at 11:31:39PM +0100, Éric Piel wrote:
> On 13-12-13 21:54, Sebastian Reichel wrote:
> >The lis302 has already a DT binding described in [0],
> >which descibes misc. hardware properties. The current
> >binding does not support all values needed to convert
> >the Nokia N900's platform data to DT.
> >
> >This patchset introduces support for describing inverted
> >axis, configuration of second wakeup unit and wakeup
> >threshold support.
> 
> All the three patches related to the lis3lv02d driver look fine to me.
> Here is my signed-off for patches 2, 3, and 4:
> Signed-off-by: Éric Piel <eric.piel-VkQ1JFuSMpfAbQlEx87xDw@public.gmane.org>
> 
> I've got 2 side questions:
>  * How do you write a negative value in a DTS file? Is this just the
> very standard way (i.e., -), or do you need to use a specific
> technique (such as 2-completemnt on 32 bits)? If it's not the
> standard way, it should probably be documented somewhere.

One can simply use -, but one has to put the value into (). This is
because DT supports simple mathematical operations for the values,
e.g. 5-10 and must have some way to distinguish between (5) (-10)
and (5-10).

Here is an example for N900 axis configuration from DT file:

 st,axis-x = <1>;    /* LIS3_DEV_X */
 st,axis-y = <(-2)>; /* LIS3_INV_DEV_Y */
 st,axis-z = <(-3)>; /* LIS3_INV_DEV_Z */

I had some trouble to find this out myself, so probably its a good
idea to document this somewhere.

>  * Who wants to carry these patches? Can they all go via the
> devicetree branch? Or maybe Arnd or Greg would prefer to pick them
> via the misc driver branch? Both ways are fine for me...

I don't care, but it would be nice to see this in 3.14.

-- Sebastian

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