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Date: Wed, 26 May 2010 12:51:36 +0200
From: Florian Mickler <florian@mickler.org>
To: Arve =?ISO-8859-15?B?SGr4bm5lduVn?= <arve@android.com>
Newsgroups: gmane.linux.documentation,gmane.linux.kernel
Cc: Peter Zijlstra <peterz@infradead.org>, linux-pm@lists.linux-foundation.org,
       linux-kernel@vger.kernel.org, "Rafael J. Wysocki" <rjw@sisk.pl>,
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       Pavel Machek <pavel@ucw.cz>, Magnus Damm <damm@igel.co.jp>,
       Cornelia Huck <cornelia.huck@de.ibm.com>,
       Nigel Cunningham <nigel@tuxonice.net>, linux-doc@vger.kernel.org
Subject: Re: [PATCH 2/8] PM: suspend_block: Add driver to access suspend 
 blockers from user-space
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On Wed, 26 May 2010 03:47:27 -0700
Arve Hjønnevåg <arve@android.com> wrote:

> 2010/5/26 Peter Zijlstra <peterz@infradead.org>:
> > On Fri, 2010-05-21 at 15:46 -0700, Arve Hjønnevåg wrote:
> >> +To create a suspend blocker from user space, open the suspend_blocker
> >> special
> >> +device file:
> >> +
> >> +    fd = open("/dev/suspend_blocker", O_RDWR | O_CLOEXEC);
> >> +
> >> +then optionally call:
> >> +
> >> +    ioctl(fd, SUSPEND_BLOCKER_IOCTL_SET_NAME(strlen(name)), name);
> >> +
> >> +To activate the suspend blocker call:
> >> +
> >> +    ioctl(fd, SUSPEND_BLOCKER_IOCTL_BLOCK);
> >> +
> >> +To deactivate it call:
> >> +
> >> +    ioctl(fd, SUSPEND_BLOCKER_IOCTL_UNBLOCK);
> >> +
> >> +To destroy the suspend blocker, close the device:
> >> +
> >> +    close(fd);
> >
> > Urgh, please let the open() be BLOCK, the close() be UNBLOCK, and keep
> > the SET_NAME thing if you really care.
> >
> 
> That would be very inefficient.
> 

Also I think it is intended to enforce named suspend blockers. (For
debugging/accounting purposes).

Cheers,
Flo