Re: [PATCH] Input: gpio_keys: Add level trigger support for GPIO keys

On Fri, Feb 9, 2018 at 11:23 AM, Baolin Wang [off-list ref] wrote:

On 9 February 2018 at 14:39, Dmitry Torokhov [off-list ref] wrote:

quoted

On Thu, Feb 8, 2018 at 10:08 PM, Baolin Wang [off-list ref] wrote:

quoted

On some platforms (such as Spreadtrum platform), the GPIO keys can only
be triggered by level type.

How do you stop the interrupt from re-triggering as long as the key
stays pressed?

We will set the level type irq handler as handle_level_irq(), in this
function, it will mask and ack the irq firstly.

Wouldn't be ambiguous?

1. User presses the key ->
  a) we got edge followed by level signaling;
  b) IRQ core masks line, calls handler, ACKs, unmasks;
  c) somewhere here Press Event is sent;
  d) we still have level... We get IRQ fired again? But see 1. It
obviously not the case.
2. User releases the key ->
  ...

So, the main question if I understood Dmitry correctly is the period
in time where IRQ line should be masked on one hand, and on the other
it will guarantee that user didn't release-press cylcle.

-- 
With Best Regards,
Andy Shevchenko
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