staging: iio: ak8975: make gpio platdata mandatory

[Russell King - ARM Linux]

On Sun, Mar 06, 2011 at 09:31:41AM +0900, Naveen Krishna Ch wrote:
> Hi Kyungmin Park,
> 
> On 4 March 2011 14:51, Kyungmin Park <kmpark at infradead.org> wrote:
> > Hi,
> >
> > On Fri, Mar 4, 2011 at 2:34 PM, Naveen Krishna Ch
> > <naveenkrishna.ch at gmail.com> wrote:
> >> Issue:
> >> For some architectures CONFIG_GENERIC_GPIO is defined,
> >> leaving irq_to_gpio undefined.  Causing build break.
> >
> > It's better to implement the irq_to_gpio. Since gpio_to_irq is already
> > implemented. it's just vice versa.
> Implementing such macros in machine header files leads to inclusion of
> mach/gpio.h or irqs.h
> Russel King, seems against to the same...

Four reasons:

1. including mach/gpio.h means that the code is non-portable to other
   architectures.
2. linux/gpio.h defines helpers for the !GENERIC_GPIO case.
3. it's good practice to always use linux/ includes rather than asm/ or
   mach/ where-ever possible.
4. over time, standard helpers tend to get split out into the common
   architecture-independent header files.  Who would like to volunteer
   to fix up all the mach/gpio.h->linux/gpio.h when that happens.

However:
> >> For some architectures CONFIG_GENERIC_GPIO is defined,
> >> leaving irq_to_gpio undefined.  Causing build break.

I read this as saying: "There are architectures which set
CONFIG_GENERIC_GPIO but do not provide a definition for irq_to_gpio()".
If that's true, then that's a problem for those architectures to solve.

However, first I'd like you to clear up some confusion: what do you mean
by architecture?  ARM/Sparc/x86?  Or S3C2410 vs OMAP4430 vs Orion vs
Tegra?  The former are architectures.  The latter are SoCs or families
of SoCs/machines/platforms.

Last point: do _not_ cc: mailing list managers for normal discussion
email - I'm talking about the majordomo at vger.kernel.org which was in the
CC in this thread.  Mailing list managers take specially formatted email
messages in order to take automated action.  They do not recognise plain
language, and you'll probably get a verbose error reply.