linux-kernel - Re: [PATCH 2/8] PM: suspend_block: Add driver to access suspend blockers from user-space

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Message-ID: <AANLkTilNUEhuPvCqh3lItwX3qBLyCghWRlep-aENwsiw@mail.gmail.com>
Date:	Wed, 26 May 2010 16:13:45 -0700
From:	Arve Hjønnevåg <arve@...roid.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Randy Dunlap <rdunlap@...otime.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>,
	Jim Collar <jim.collar@...are.net>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Avi Kivity <avi@...hat.com>, Len Brown <len.brown@...el.com>,
	Pavel Machek <pavel@....cz>, Magnus Damm <damm@...l.co.jp>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	Nigel Cunningham <nigel@...onice.net>,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH 2/8] PM: suspend_block: Add driver to access suspend 
	blockers from user-space

2010/5/26 Peter Zijlstra <peterz@...radead.org>:
> On Wed, 2010-05-26 at 03:47 -0700, Arve Hjønnevåg wrote:
>> 2010/5/26 Peter Zijlstra <peterz@...radead.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.
>
> How so? Anyway, since you admitted this thing isn't needed at all, I say
> we remove it altogether.
>

I also said it was useful. I don't think we should drop it just
because we can work around its absence.

-- 
Arve Hjønnevåg
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