linux-kernel - Re: [patch 4/4] hpet: factor timer allocate from open

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Message-Id: <20120306103805.5d8e0d09.akpm@linux-foundation.org>
Date:	Tue, 6 Mar 2012 10:38:05 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Clemens Ladisch <clemens@...isch.de>
Cc:	Thomas Gleixner <tglx@...utronix.de>, maglyx@...il.com,
	Arnd Bergmann <arnd@...db.de>,
	John Stultz <johnstul@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch 4/4] hpet: factor timer allocate from open

On Tue, 06 Mar 2012 16:04:21 +0100
Clemens Ladisch <clemens@...isch.de> wrote:

> Thomas Gleixner wrote:
> > On Mon, 5 Mar 2012, akpm@...ux-foundation.org wrote:
> >> From: Magnus Lynch <maglyx@...il.com>
> >> Subject: hpet: factor timer allocate from open
> >>
> >> The current implementation of the /dev/hpet driver couples opening the
> >> device with allocating one of the (scarce) timers (aka comparators).  This
> >> is a limitation in that the main counter may be valuable to applications
> >> seeking a high-resolution timer who have no use for the interrupt
> >> generating functionality of the comparators.
> >>
> >> This patch alters the open semantics so that when the device is opened, no
> >> timer is allocated.  Operations that depend on a timer being in context
> >> implicitly attempt allocating a timer, to maintain backward compatibility.
> >
> > AFAICT, there is only fasync which calls hpet_alloc_timer(). All other
> > functions are broken by this chage.
> 
> Indeed.  There was another call in hpet_ioctl_common(), but it appears
> that one somehow got dropped.
> 
> Magnus, is this the patch that you submitted and have tested?

I've been carrying this patch since March 2010 - perhaps it rotted.
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