Status of SPI bitbang / accelerometers

Nelson Castillo arhuaco at
Wed Jan 7 12:53:45 CET 2009

On Wed, Jan 7, 2009 at 1:40 AM, Simon Kagstrom <simon.kagstrom at> wrote:
> On Tue, 6 Jan 2009 23:20:55 -0500
> "Nelson Castillo" <arhuaco at> wrote:
>> Is anyone working on this?
>> Has anything changed since then?
> No, I started looking at it, but my head went buzzing from looking into
> the SPI code (layers upon layers!). I guess you are already aware of
> this, but for other readers of the thread: It's not really a
> functionality issue but something needed to upstream the driver.

Simon, thanks for your reply. Let's see how it goes... If it is too
hard I'll try to fail fast :-)

> Using the current SPI interface is too slow on the openmoko and also not
> really safe since it cannot be operated in interrupt mode. Andys
> implementation simply communicates with the accelerometers manually so
> everything is fine there. But not for upstream, which tends to
> dislike duplicated efforts.
> The idea we discussed was therefore to add a synchronous SPI transfer
> function, which can be called from interrupt context. It was posted
> further up in your thread:
> the problems which got me dizzy was the layering of SPI, which I never
> really got the hang of. Also, if you want to work on this, I've found
> the eclipse code navigation to be really, really nice (makes it easy to
> lookup all implementations of the interfaces etc). I've written a small
> guide for how to set it up for the kernel here:

Thanks. I've had good luck with cscope so far (cscope -k -R). I might
check this out.

> The patch with what I got so far is below. It's not much really, the
> big function is just a copy of bitbang_work, and I think you can
> safely ignore it.

I'll read it. I'll ask questions in the list once I have them :-)


More information about the openmoko-kernel mailing list