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

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Message-ID: <20100424055523.GC2290@elf.ucw.cz>
Date:	Sat, 24 Apr 2010 07:55:23 +0200
From:	Pavel Machek <pavel@....cz>
To:	Arve Hj?nnev?g <arve@...roid.com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	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 2010-04-23 20:20:47, Arve Hj?nnev?g wrote:
> On Fri, Apr 23, 2010 at 9:43 AM, Alan Stern <stern@...land.harvard.edu> wrote:
> > 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()?
> >
> 
> I prefer using ioctls. We have three operations at the moment. Init,
> block and unblock. If we do init with write but block and unblock
> using ioctls, it would be pretty strange. Specifying a command and

Why would it be "strange"?

> argument in a string to write is more complicated to parse than using
> ioctls.

More complicated to parse?

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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