linux-kernel - Re: [patch 2.6.26] /dev/hpet

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Date:	Fri, 25 Jul 2008 12:55:35 -0700
From:	David Brownell <david-b@...bell.net>
To:	Clemens Ladisch <clemens@...isch.de>
Cc:	lkml <linux-kernel@...r.kernel.org>, bob.picco@...com,
	venkatesh.pallipadi@...el.com, Vojtech Pavlik <vojtech@...e.cz>,
	the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [patch 2.6.26] /dev/hpet - fixes and cleanup

On Thursday 24 July 2008, Clemens Ladisch wrote:
> David Brownell wrote:

> > > This seems to be the only part of the userspace interface that is
> > > used in practice.  Because of the availability of POSIX timers, it might
> > > make sense to deprecate the HPET ioctl interface.
> >
> > I'll leave that part up to someone else.  If POSIX timers
> > are a sufficient userspace interface, great ... then that
> > mmap son't really be needed either!
> 
> The idea is to be able to get a high-precision timer value without doing
> a syscall.  (Whether the syscall overhead actually matters in a specific
> application is another question.)

On x86_64 the vsyscall stuff should kick in for gettimeofday()
when HPET is in use, eliminating the need for /dev/hpet mmapping.

I don't really know vsyscalls ... but if that could be done on
i386 systems, the last argument for /dev/hpet would seem gone...
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