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

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Date:	Wed, 5 May 2010 14:37:39 -0700
From:	Brian Swetland <swetland@...gle.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	mark gross <mgross@...ux.intel.com>, markgross@...gnar.org,
	Len Brown <len.brown@...el.com>, linux-doc@...r.kernel.org,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [linux-pm] [PATCH 1/8] PM: Add suspend block api.

On Wed, May 5, 2010 at 2:12 PM, Alan Stern <stern@...land.harvard.edu> 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.  It would go like this:
>
>        The modem IRQ handler queues its event to the input subsystem.
>        As it does so the input subsystem enables a suspend blocker,
>        causing the system to stay awake after the IRQ is done.
>
>        The user program enables its own suspend blocker before reading
>        the input queue.  When the queue is empty, the input subsystem
>        releases its suspend blocker.
>
>        When the user program finishes processing the event, it
>        releases its suspend blocker.  Now the system can go back to
>        sleep.
>
> 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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