Re: GPIO expander for p2041

On Tue, 2016-03-01 at 15:41 +0000, Nora Björklund wrote:

Hi,

I was working on a p2041rdb target not so long ago and needed to use
the gpio pins (described in detail in the p2041 reference manual),
these are visible on the p2041 fact sheet [1]. The pins are connected
to a gpio expander, PCA9672 [2], which is connected to a i2c-bus. 

The expander was not available in the device-tree for p2041rdb so I
patched it locally to include it. The gpio-expander does not seem to be
available in any upstream repository either (at this time I was working
on a version of the 3.12 kernel, but it seems to be the same for the
one I obtained from
git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git).

Would this patch be of any interest for the upstream powerpc kernel?
The gpio pins are there on all p2041rdb targets (at least since they
are mentioned as such in the reference guide), so I could not come up
with a reason to why it is excluded from the device tree.

In theory the device tree should completely describe the hardware, regardless
of what Linux looks for, but in practice some things get missed and then get
added as they're needed.

Yes, a patch would be welcome.

-Scott