Date: Sun, 16 Dec 2012 09:18:50 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Alexander Motin <mav@freebsd.org> Cc: svn-src-projects@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r244287 - projects/calloutng/sys/x86/isa Message-ID: <CAJ-Vmok7rdooCifWmNw2LJ95BSuOwwz6wPeq86x8AcAp7FzuJw@mail.gmail.com> In-Reply-To: <50CE009B.7010804@FreeBSD.org> References: <201212161116.qBGBGEwn063983@svn.freebsd.org> <CAJ-VmonYuh4dTwY9PjBmE4uOq8nNAL_kDKXpi6knwvc99PqJcw@mail.gmail.com> <50CE009B.7010804@FreeBSD.org>
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On 16 December 2012 09:10, Alexander Motin <mav@freebsd.org> wrote: > This change affects only one-shot operation mode of i8254 eventtimer, which > we can't enable by default because it can't coexist with i8254 timecounter, > which we can't disable by default because we can't be sure that there is any > other timecounter. That is why I've written about fun. And no, I have no > all possible weird i8254 clones to test, so any help and ideas are welcome. > :) That's why I think you guys have to be very careful here. There's still plenty of embedded x86 hardware out there which uses not-quite-matching i8254 silicon implementations. I realise it's not enabled by default, but by putting this code in there, you risk having it eventually bubble up and become potentially available/active on some quirky embedded platforms (or heck, non-embedded platforms where for some reason the i8254 eventtimer is active, but the timecounter isn't.) The point I'm trying to make here is that you guys shouldn't just change things because you don't think that it'll not be used. You may not think it's being used but the whole i386 space (embedded or otherwise) is full of legacy (and non-legacy) hilarity. You should be really careful that you don't break previous things which you just don't have a chance in hell of being able to test thoroughly. We have 15 years of "mostly working" on a really really quirky platform. You won't get that kind of testing again. I'm (kind of) sorry for being overly serious and ranty here - but this is exactly the kind of thing that breaks hardware support in unpredictable ways, making us all look bad. Adrian
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