Date: Sat, 14 Sep 2013 16:56:38 -0700 From: Adrian Chadd <adrian@freebsd.org> To: Ian Lepore <ian@freebsd.org> Cc: John-Mark Gurney <jmg@funkthat.com>, FreeBSD PowerPC ML <freebsd-ppc@freebsd.org>, "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org>, freebsd-sparc64 <freebsd-sparc64@freebsd.org> Subject: Re: Patch for Cross-Reference Phandles Message-ID: <CAJ-Vmonk_cjc%2BwfCqsHdVESMvRMQTP4c2myK9jZr_%2B59GmWLQQ@mail.gmail.com> In-Reply-To: <1379181341.1197.26.camel@revolution.hippie.lan> 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> <1379181341.1197.26.camel@revolution.hippie.lan>
next in thread | previous in thread | raw e-mail | index | archive | help
... holy crap. :-) erm, try writing some code that does something with it: int foo[2] = { 0, 0 }; main() { int i; for (i = 0; i < 2; i++) { foo[i] = i; } } .. and then make foo[2] be foo[512] and explicitly set it up to be zero'ed. see what happens. -a On 14 September 2013 10:55, Ian Lepore <ian@freebsd.org> wrote: > 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 <compile> -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 > > > _______________________________________________ > freebsd-ppc@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-ppc > To unsubscribe, send any mail to "freebsd-ppc-unsubscribe@freebsd.org" >
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAJ-Vmonk_cjc%2BwfCqsHdVESMvRMQTP4c2myK9jZr_%2B59GmWLQQ>