linux-kernel - Re: [linux-pm] [PATCH 2/9] PM: suspend_block: Add driver to access suspend blockers from user-space

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Date:	Fri, 23 Apr 2010 12:43:46 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Pavel Machek <pavel@....cz>
cc:	Arve Hj??nnev??g <arve@...roid.com>,
	Len Brown <len.brown@...el.com>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Magnus Damm <damm@...l.co.jp>,
	<linux-pm@...ts.linux-foundation.org>
Subject: Re: [linux-pm] [PATCH 2/9] PM: suspend_block: Add driver to access
 suspend blockers from user-space

On Fri, 23 Apr 2010, Pavel Machek wrote:

> Hi!
> 
> > Add a misc device, "suspend_blocker", that allows user-space processes
> > to block auto suspend. The device has ioctls to create a suspend_blocker,
> > and to block and unblock suspend. To delete the suspend_blocker, close
> > the device.
> > 
> > Signed-off-by: Arve Hj??nnev??g <arve@...roid.com>
> 
> > --- a/Documentation/power/suspend-blockers.txt
> > +++ b/Documentation/power/suspend-blockers.txt
> > @@ -95,3 +95,20 @@ if (list_empty(&state->pending_work))
> >  else
> >  	suspend_block(&state->suspend_blocker);
> >  
> > +User-space API
> > +==============
> > +
> > +To create a suspend_blocker from user-space, open the suspend_blocker device:
> > +    fd = open("/dev/suspend_blocker", O_RDWR | O_CLOEXEC);
> > +then call:
> > +    ioctl(fd, SUSPEND_BLOCKER_IOCTL_INIT(strlen(name)), name);
> 
> 
> This seems like very wrong idea -- it uses different ioctl number for
> each length AFAICT.

How about specifying the name by an ordinary write() call instead of
by an ioctl()?

Alan Stern

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