Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261776AbVCNTwL (ORCPT ); Mon, 14 Mar 2005 14:52:11 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261779AbVCNTwL (ORCPT ); Mon, 14 Mar 2005 14:52:11 -0500 Received: from waste.org ([216.27.176.166]:10919 "EHLO waste.org") by vger.kernel.org with ESMTP id S261776AbVCNTvs (ORCPT ); Mon, 14 Mar 2005 14:51:48 -0500 Date: Mon, 14 Mar 2005 11:51:10 -0800 From: Matt Mackall To: john stultz Cc: Christoph Lameter , lkml , Tim Schmielau , George Anzinger , albert@users.sourceforge.net, Ulrich Windl , Dominik Brodowski , David Mosberger , Andi Kleen , paulus@samba.org, schwidefsky@de.ibm.com, keith maanthey , Patricia Gaughen , Chris McDermott , Max Asbock , mahuja@us.ibm.com, Nishanth Aravamudan , Darren Hart , "Darrick J. Wong" , Anton Blanchard , donf@us.ibm.com Subject: Re: [RFC][PATCH] new timeofday core subsystem (v. A3) Message-ID: <20050314195110.GD32638@waste.org> References: <1110590655.30498.327.camel@cog.beaverton.ibm.com> <20050313004902.GD3163@waste.org> <1110825765.30498.370.camel@cog.beaverton.ibm.com> <20050314192918.GC32638@waste.org> <1110829401.30498.383.camel@cog.beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1110829401.30498.383.camel@cog.beaverton.ibm.com> User-Agent: Mutt/1.5.6+20040907i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2281 Lines: 50 On Mon, Mar 14, 2005 at 11:43:21AM -0800, john stultz wrote: > On Mon, 2005-03-14 at 11:29 -0800, Matt Mackall wrote: > > On Mon, Mar 14, 2005 at 10:42:45AM -0800, john stultz wrote: > > > > > > > > +static inline cycle_t read_timesource(struct timesource_t* ts) > > > > > +{ > > > > > + switch (ts->type) { > > > > > + case TIMESOURCE_MMIO_32: > > > > > + return (cycle_t)readl(ts->mmio_ptr); > > > > > + case TIMESOURCE_MMIO_64: > > > > > + return (cycle_t)readq(ts->mmio_ptr); > > > > > + case TIMESOURCE_CYCLES: > > > > > + return (cycle_t)get_cycles(); > > > > > + default:/* case: TIMESOURCE_FUNCTION */ > > > > > + return ts->read_fnct(); > > > > > + } > > > > > +} > > > > > > > > Wouldn't it be better to change read_fnct to take a timesource * and > > > > then change all the other guys to generic_timesource_ helper > > > > functions? This does away with the switch and makes it trivial to add > > > > new generic sources. Change mmio_ptr to void *private. > > > > > > Not sure if I totally understand this, but originally I just had a read > > > function, but to allow this framework to function w/ ia64 fsyscalls (and > > > likely other arches vsyscalls) we need to pass the raw mmio pointers. > > > Thus the timesource type and switch idea was taken from the time > > > interpolator code. > > > > Well for vsyscall, we can leave the mmio_ptr and type. But in-kernel, > > I think we'd rather always call read_fnct with generic helpers than hit this > > switch every time. > > Huh. So if I understand you properly, all timesources should have valid > read_fnct pointers that return the cycle value, however we'll still > preserve the type and mmio_ptr so fsyscall/vsyscall bits can use them > externally? Well where we'd read an MMIO address, we'd simply set read_fnct to generic_timesource_mmio32 or so. And that function just does the read. So both that function and read_timesource become one-liners and we drop the conditional branches in the switch. -- Mathematics is the supreme nostalgia of our time. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/