Re: [PATCH v2] gpio: convince line to become input in irq helper

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Wed, Jul 6, 2016 at 11:07 AM, Grygorii Strashko
<grygorii.strashko@xxxxxx> wrote:

> first of all for slow GPIO controllers (like pcf857x) it might be unsafe to call
> .direction_input() from .irq_request_resources() callback because it
> will be called in atomic context under raw_spin_lock_irqsave().
>
>
> __setup_irq
>    |- raw_spin_lock_irqsave()
>         |- irq_request_resources()
>         |- [ __irq_set_trigger() ]
>         |- [ irq_startup() ]
>         |- [ __enable_irq() ]
>    |- raw_spin_unlock_irqrestore()
>
> [and it can be unsafe for fast GPIO chips also ;( , for example if it's
> required to do some kind of PM management actions before accessing HW - most of
> drivers expect their GPIOchip callbacks to be called only after gpiochip.request() or
> .irq_startup().]
>
> In  my opinion this change breaks orthogonality of IRQchip vs GPIOchip interfaces
> because it adds and (what is more important) hides call of GPIOchip callback
> from inside IRQchip interface somewhere in  the depths of gpiolib framework.
> As result, GPIO drivers lose possibility to properly handle GPIO vs IRQ interface's
> differences like: locking, slow vs fast, hw specific settings, features of frameworks.
>
> I propose to revert it, sry,

Aw typical, you are right.

OK I'll take this patch and it's fixes out of the GPIO tree :(

Yours,
Linus Walleij
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