Re: [RFC PATCH v2 07/16] gpio: Add support for unified device properties interface

Arnd Bergmann
2014-09-23T15:46:13Z

On Tuesday 23 September 2014 17:25:50 Linus Walleij wrote:
> On Tue, Sep 16, 2014 at 1:52 PM, Mika Westerberg
> <mika.westerberg@linux.intel.com> wrote:
>
> > Some drivers need to deal with only firmware representation of its
> > GPIOs. An example would be a GPIO button array driver where each button
> > is described as a separate firmware node in device tree. Typically these
> > child nodes do not have physical representation in the Linux device
> > model.
> >
> > In order to help device drivers to handle such firmware child nodes we
> > add dev[m]_node_get_named_gpiod() that takes a firmware node pointer as
> > parameter, finds the GPIO using whatever is the underlying firmware
> > method, and requests the GPIO properly.
> >
> > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
>
> I have a hard time figuring out if this is what we want for common
> accessors between DT and ACPI.
>
> Can I get some input from Grant, Arnd, Mark, Darren...?

I just took a brief look at this. My first impression is that the
fw_dev_node structure is weird when all callers just do (in patch 2)

+ struct fw_dev_node fdn = {
+ .of_node = dev->of_node,
+ .acpi_node = ACPI_COMPANION(dev),
+ };

I'd much rather see an interface that passes the 'struct device'
pointer down to dev_get_named_gpiod() and all other exported
functions, and then internally does the conversion at the point
where the access is done.

Arnd