From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964808AbWGYTGy (ORCPT ); Tue, 25 Jul 2006 15:06:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964809AbWGYTGy (ORCPT ); Tue, 25 Jul 2006 15:06:54 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:1978 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S964808AbWGYTGx (ORCPT ); Tue, 25 Jul 2006 15:06:53 -0400 Subject: Re: [PATCH] RTC: Add mmap method to rtc character driver From: Arjan van de Ven To: Neil Horman Cc: linux-kernel@vger.kernel.org, a.zummo@towertech.it, jg@freedesktop.org In-Reply-To: <20060725190357.GG4608@hmsreliant.homelinux.net> References: <20060725174100.GA4608@hmsreliant.homelinux.net> <1153850139.8932.40.camel@laptopd505.fenrus.org> <20060725182208.GD4608@hmsreliant.homelinux.net> <1153852375.8932.41.camel@laptopd505.fenrus.org> <20060725184328.GF4608@hmsreliant.homelinux.net> <1153853596.8932.44.camel@laptopd505.fenrus.org> <20060725190357.GG4608@hmsreliant.homelinux.net> Content-Type: text/plain Organization: Intel International BV Date: Tue, 25 Jul 2006 21:06:52 +0200 Message-Id: <1153854412.8932.46.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > > well the idea that has been tossed about a few times is using a vsyscall > > function that either calls into the kernel, or directly uses the hpet > > page (which can be user mapped) to get time information that way... > > or even would use rdtsc in a way the kernel knows is safe (eg corrected > > for the local cpu's speed and offset etc etc). > > > Ok, that makes sense, although thats only going to be supportable on hpet > enabled systems right? well it's only going to be *fast* on hpet enabled systems (which should be the *vast* majority nowadays if it wasn't for some silly bios defaults by some vendors); all others can just fall back to other methods. The beauty of the vsyscall concept :) -- if you want to mail me at work (you don't), use arjan (at) linux.intel.com