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

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Date:	Thu, 24 Jul 2008 13:35:57 +0200
From:	Clemens Ladisch <clemens@...isch.de>
To:	David Brownell <david-b@...bell.net>
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

David Brownell wrote:
> I didn't find any software using /dev/hpet, except for
> the example in Documentation/hpet.txt ... presumably I
> was looking in the wrong place. I'd surely have retched
> at anything mmapping hardware registers though.  ;)

http://subversion.jackaudio.org/jack/trunk/jack/config/os/gnu-linux/time.c

> > 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.)


Regards,
Clemens
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