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

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Message-ID: <alpine.LFD.2.02.1203061345150.2742@ionos>
Date:	Tue, 6 Mar 2012 13:52:41 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	akpm@...ux-foundation.org
cc:	maglyx@...il.com, Arnd Bergmann <arnd@...db.de>,
	clemens@...isch.de, John Stultz <johnstul@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch 4/4] hpet: factor timer allocate from open

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.

>  There is also an IOCTL (HPET_ALLOC_TIMER _IO) added so that the
> allocation may be done explicitly.  (I prefer the explicit open then

And that IOCTL does what? Return 0 is not really useful functionality.

Thanks,

	tglx
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