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

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Message-ID: <4F562775.2010501@ladisch.de>
Date:	Tue, 06 Mar 2012 16:04:21 +0100
From:	Clemens Ladisch <clemens@...isch.de>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	akpm@...ux-foundation.org, 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

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?


Regards,
Clemens
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