Re: [[RFC PATCH]] gpio: gpio-mxc: make sure gpio is input when request IRQ

[Linus Walleij <linus.walleij-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

On Thu, Jul 24, 2014 at 10:12 AM, Markus Niebel
<list-09_linux_arm-7U5DVgMjAv4@public.gmane.org> wrote:
> Am 23.07.2014 18:14, wrote Linus Walleij:

>> So always prepare the hardware and make it ready for action in respective
>> callbacks from the GPIO and irqchip APIs. Do not rely on gpiod_to_irq() having
>> been called first.
>>
>
> So a gpio driver is responsible to read status of gpio lines and flag any gpio line
> currently configured as out (base on the information read from hardware registers)
> on driver probe time - correct?

I don't think anyone reads that information explicitly to set up
these flags.

Drivers just leave the pins in their power-on maiden state without
trying to figure out how they're set-up. But as you say, if you call
gpiod_get_direction() on them, the flag gets set up indeed.

So usually these flags are set by code, calling
gpiod_[get/set]_direction().
Then they do get flagged as outputs or inputs.

> If yes is the driver allowed to call
> gpiod_get_direction() to have the FLAG_IS_OUT set in the gpiolib layer?

I don't know if it'd be a good idea to loop over all gpios in a new
irqchip and fetch the direction just to get the flags right, so far
we haven't done that and I don't know what the usecase would be.

If we need that we should do it in gpiolib for all drivers don't you
think?

But then we need a rationale for doing it, other than it's nice :-)
It is already called on-the-fly by debugfs when a user needs that
info.

Yours,
Linus Walleij
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