From owner-freebsd-ppc@FreeBSD.ORG Sat Sep 14 17:55:46 2013 Return-Path: Delivered-To: freebsd-ppc@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id 36196417; Sat, 14 Sep 2013 17:55:46 +0000 (UTC) (envelope-from ian@FreeBSD.org) Received: from mho-01-ewr.mailhop.org (mho-03-ewr.mailhop.org [204.13.248.66]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id E9B9021F7; Sat, 14 Sep 2013 17:55:45 +0000 (UTC) Received: from c-24-8-230-52.hsd1.co.comcast.net ([24.8.230.52] helo=damnhippie.dyndns.org) by mho-01-ewr.mailhop.org with esmtpsa (TLSv1:AES256-SHA:256) (Exim 4.72) (envelope-from ) id 1VKu4O-00074h-Lj; Sat, 14 Sep 2013 17:55:44 +0000 Received: from [172.22.42.240] (revolution.hippie.lan [172.22.42.240]) by damnhippie.dyndns.org (8.14.3/8.14.3) with ESMTP id r8EHtfLF010841; Sat, 14 Sep 2013 11:55:41 -0600 (MDT) (envelope-from ian@FreeBSD.org) X-Mail-Handler: Dyn Standard SMTP by Dyn X-Originating-IP: 24.8.230.52 X-Report-Abuse-To: abuse@dyndns.com (see http://www.dyndns.com/services/sendlabs/outbound_abuse.html for abuse reporting information) X-MHO-User: U2FsdGVkX18HhcAWuRO6t29SuGbzw4AI Subject: Re: Patch for Cross-Reference Phandles From: Ian Lepore To: John-Mark Gurney In-Reply-To: <20130914172735.GX68682@funkthat.com> References: <522CC7E0.9060508@freebsd.org> <5231D8A6.9080501@freebsd.org> <20130914133155.GA32845@alchemy.franken.de> <52346D71.4080407@freebsd.org> <1379173405.1197.7.camel@revolution.hippie.lan> <20130914172735.GX68682@funkthat.com> Content-Type: text/plain; charset="us-ascii" Date: Sat, 14 Sep 2013 11:55:41 -0600 Message-ID: <1379181341.1197.26.camel@revolution.hippie.lan> Mime-Version: 1.0 X-Mailer: Evolution 2.32.1 FreeBSD GNOME Team Port Content-Transfer-Encoding: 7bit Cc: freebsd-arm@FreeBSD.org, freebsd-sparc64 , freebsd-ppc@FreeBSD.org X-BeenThere: freebsd-ppc@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Porting FreeBSD to the PowerPC List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 14 Sep 2013 17:55:46 -0000 On Sat, 2013-09-14 at 10:27 -0700, John-Mark Gurney wrote: > Ian Lepore wrote this message on Sat, Sep 14, 2013 at 09:43 -0600: > > On Sat, 2013-09-14 at 09:06 -0500, Nathan Whitehorn wrote: > > > On 09/14/13 08:31, Marius Strobl wrote: > > > > On Thu, Sep 12, 2013 at 10:07:18AM -0500, Nathan Whitehorn wrote: > > > >> On 09/08/13 13:54, Nathan Whitehorn wrote: > > > >>> Open Firmware has three namespaces for handles: > > > >>> 1. Instance handles, for open devices > > > >>> 2. Package handles for the client interface > > > >>> 3. Package handles for device tree cross references > > > >>> > > > >>> On Powermac hardware, we assume that (2) and (3) are identical and > > > >>> call both phandles. On embedded FDT systems, you can't open devices > > > >>> and so we abuse ihandle_t for (3). IBM pSeries hardware, however, has > > > >>> all three things. With that in mind, I'd like to start separating > > > >>> them. The patch at > > > >>> http://people.freebsd.org/~nwhitehorn/xref_phandle.diff adds a new > > > >>> function (OF_child_xref_phandle) that takes a phandle of type (3) and > > > >>> turns into one of type (2) by searching for entries named "phandle", > > > >>> "ibm,phandle", or "linux,phandle" in the tree. This should work for > > > >>> FDT as well, but is not connected in the patch to anything actually > > > >>> FDT related. > > > >>> > > > >>> Comments would be appreciated. I'd like to get to get this as in as > > > >>> soon as possible (given the HEAD freeze) otherwise. > > > >>> -Nathan > > > >> Since I haven't heard anything, it shouldn't affect any existing > > > >> platforms or code, and it would be nice to have this interface available > > > >> in the 10.x series, I plan to ask re@ for commit approval tomorrow. > > > >> Please let me know if there are any objections. > > > > Technically that patch is fine. It would be nice if you could fix the > > > > style bugs before committing, though. In OF_child_xref_phandle(), the > > > > variables should go above the comment and you don't need to initialize > > > > the static global one in ofw_pcibus.c to zero explicitly. If you do > > > > nevertheless, spaces should go before and after the '='. > > > > > > > > > > Thanks! I think the explicit zero initialization adds some clarity for > > > people reading the code, so I'd like to keep it. The rest of the changes > > > have been made. > > > -Nathan > > > > The explicit zero init also makes it 4 bytes harder to fit the kernel > > into a small flash on embedded systems. We should be eliminating > > zero-inits that move items from bss to data, not adding new ones. > > I just ran a simple test: > int foo = 0; > > and compiled it, both with: > FreeBSD clang version 3.3 (tags/RELEASE_33/final 183502) 20130610 > Target: x86_64-unknown-freebsd10.0 > Thread model: posix > > and: > FreeBSD clang version 3.3 (trunk 178860) 20130405 > Target: armv6--freebsd > Thread model: posix > > and: > gcc (GCC) 4.2.1 20070831 patched [FreeBSD] > Copyright (C) 2007 Free Software Foundation, Inc. > This is free software; see the source for copying conditions. There is NO > warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. > > all are smart enough to know that zero init is the same as locating it > in bss, and do so... and not put it in data... Oh, these were all > compiled w/o any options, just -c foo.c... > Huh. That's pretty surprising to me, because IMO, an explicit zero-init is NOT the same as putting it in bss, it's explicitly a way to say "I want this in the data segment." I guess there are other ways to control placement these days. -- Ian