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SubjectRe: [PATCH] extcon: gpio: Request reasonable interrupts
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On 19. 6. 8. 오전 6:24, Linus Walleij wrote:
> On Tue, Jun 4, 2019 at 3:30 AM Chanwoo Choi <cw00.choi@samsung.com> wrote:
>> On 19. 5. 31. 오전 3:39, Linus Walleij wrote:
>
>>> + /*
>>> + * It is unlikely that this is an acknowledged interrupt that goes
>>> + * away after handling, what we are looking for are falling edges
>>> + * if the signal is active low, and rising edges if the signal is
>>> + * active high.
>>> + */
>>> + if (gpiod_is_active_low(data->gpiod))
>>> + irq_flags = IRQF_TRIGGER_FALLING;
>>
>> If gpiod_is_active_low(data->gpiod) is true, irq_flags might be
>> IRQF_TRIGGER_LOW instead of IRQF_TRIGGER_FALLING. How can we sure
>> that irq_flags is always IRQF_TRIGGER_FALLING?
>
> OK correct me if I'm wrong, but this is an external connector and
> the GPIO goes low/high when the connector is physically inserted.
> If it was level trigged, it would lock up the CPU with interrupts until
> it was unplugged again, since there is no way to acknowledge a
> level IRQ.
>
> I think level IRQ on GPIOs are only used for logic peripherals
> such as ethernet controllers etc where you can talk to the peripheral
> and get it to deassert the line and thus acknowledge the IRQ.
>
> So the way I see it only edge triggering makes sense for extcon.
>
> Correct me if I'm wrong.

Sorry for late reply because of vacation.

Actually, I have not thought that the kind of irq_flags are fixed
according to the category of specific h/w device. Until now, as I knew,
the h/w device have to initialize the the kind of irq_flags
for each peripheral device dependency. The each vendor of peripheral device
might design the kind of the kind of irq-flags for detection.

If possible, could you provide some example on mainline kernel?

--
Best Regards,
Chanwoo Choi
Samsung Electronics

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