Re: [linux-pm] [PATCH 1/8] PM: Add suspend block api.

[Brian Swetland]

On Wed, May 5, 2010 at 2:12 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
>>
>> Oh, like tell the modem that user mode has handled the ring event and
>> its ok to un-block?
>
> No, that's not how it works. ÂIt would go like this:
>
> Â Â Â ÂThe modem IRQ handler queues its event to the input subsystem.
> Â Â Â ÂAs it does so the input subsystem enables a suspend blocker,
> Â Â Â Âcausing the system to stay awake after the IRQ is done.
>
> Â Â Â ÂThe user program enables its own suspend blocker before reading
> Â Â Â Âthe input queue. ÂWhen the queue is empty, the input subsystem
> Â Â Â Âreleases its suspend blocker.
>
> Â Â Â ÂWhen the user program finishes processing the event, it
> Â Â Â Âreleases its suspend blocker. ÂNow the system can go back to
> Â Â Â Âsleep.
>
> At no point does the user program have to communicate anything to the
> modem driver, and at no point does it have to do anything out of the
> ordinary except to enable and disable a suspend blocker.

Exactly -- and you can use the same style of overlapping suspend
blockers with other drivers than input, if the input interface is not
suitable for the particular interaction.

Brian
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