From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750777AbWG2XgD (ORCPT ); Sat, 29 Jul 2006 19:36:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750785AbWG2XgC (ORCPT ); Sat, 29 Jul 2006 19:36:02 -0400 Received: from rwcrmhc15.comcast.net ([216.148.227.155]:49650 "EHLO rwcrmhc15.comcast.net") by vger.kernel.org with ESMTP id S1750777AbWG2XgA (ORCPT ); Sat, 29 Jul 2006 19:36:00 -0400 Subject: Re: itimer again (Re: [PATCH] RTC: Add mmap method to rtc character driver) From: Nicholas Miell To: Bill Huey Cc: Edgar Toernig , Neil Horman , Jim Gettys , "H. Peter Anvin" , Dave Airlie , Segher Boessenkool , linux-kernel@vger.kernel.org, a.zummo@towertech.it, jg@freedesktop.org, Keith Packard , Ingo Molnar , Steven Rostedt In-Reply-To: <20060729225138.GA22390@gnuppy.monkey.org> References: <20060725204736.GK4608@hmsreliant.homelinux.net> <1153861094.1230.20.camel@localhost.localdomain> <44C6875F.4090300@zytor.com> <1153862087.1230.38.camel@localhost.localdomain> <44C68AA8.6080702@zytor.com> <1153863542.1230.41.camel@localhost.localdomain> <20060729042820.GA16133@gnuppy.monkey.org> <20060729125427.GA6669@localhost.localdomain> <20060729204107.GA20890@gnuppy.monkey.org> <20060729234948.0768dbf4.froese@gmx.de> <20060729225138.GA22390@gnuppy.monkey.org> Content-Type: text/plain Date: Sat, 29 Jul 2006 16:35:51 -0700 Message-Id: <1154216151.2467.5.camel@entropy> Mime-Version: 1.0 X-Mailer: Evolution 2.6.2 (2.6.2-1.fc5.5.0.njm.1) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2006-07-29 at 15:51 -0700, Bill Huey wrote: > On Sat, Jul 29, 2006 at 11:49:48PM +0200, Edgar Toernig wrote: > > Bill Huey (hui) wrote: > > > Well, this points out a serious problem with doing an mmap extension to > > > /dev/rtc. It would be better to have a page mapped by another device like > > > /dev/jiffy_counter, or something like that rather than to overload the > > > /dev/rtc with that functionality. > > > > You mean something like this, /dev/itimer? > > > > http://marc.theaimsgroup.com/?m=115412412427996 > > [CCing Steve and Ingo on this thread] > > It's a different topic than what Keith needs, but this is useful for another > set of purposes. It's something that's really useful in the RT patch since > there isn't a decent API to get at high resolution timers in userspace. What > you've written is something that I articulated to Steve Rostedt over a dinner > at OLS and is badly needed in the -rt patches IMO. I suggest targeting that > for some kind of inclusion to Ingo Molnar's patchset. > Do you mind summarizing what's wrong with the existing interfaces for those of us who didn't have the opportunity to join you for dinner at OLS? -- Nicholas Miell