Re: [PATCH] - race-free suspend. Was: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

Neil Brown
2010-06-02T10:23:00Z

On Wed, 2 Jun 2010 10:50:39 +0200
Florian Mickler <florian@mickler.org> wrote:

> On Wed, 2 Jun 2010 18:06:14 +1000
> Neil Brown <neilb@suse.de> wrote:
>
> > I cannot imagine why it would take multiple seconds to scan a keypad.
> > Can you explain that?
> >
> > Do you mean while keys are held pressed? Maybe you don't get a wake-up event
> > on key-release? In that case your user-space daemon could block suspend
> > while there are any pressed keys.... confused.
>
> IIRC, the device sends interrupts only for first key-down and
> last key-up.
> To detect simultaneous key-presses you must actively scan it after the
> first key-down.

That makes sense - thanks.
Presumably the first key-press gets to user-space promptly, so the user-space
suspend daemon can be told not to suspend until the last key-up.

Thanks,
NeilBrown