Date: Tue, 18 Jun 2013 13:17:13 -0600 From: Warner Losh <imp@bsdimp.com> To: Jung-uk Kim <jkim@FreeBSD.org> Cc: arch@freebsd.org, Niclas Zeising <zeising@freebsd.org>, Robert Millan <rmh@freebsd.org> Subject: Re: Bus space routines Message-ID: <1AF8EDA9-3403-49F2-B16F-B324084908FD@bsdimp.com> In-Reply-To: <51C0AC01.8070007@FreeBSD.org> References: <51C0345E.4000309@freebsd.org> <CAOfDtXNWMO-D1D9UAcvG_nhv4uqMQmrpEvsPd-PAEB1-FdoXtA@mail.gmail.com> <51C0AC01.8070007@FreeBSD.org>
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On Jun 18, 2013, at 12:50 PM, Jung-uk Kim wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 >=20 > On 2013-06-18 06:56:15 -0400, Robert Millan wrote: >> I think the BSD world did the right thing by introducing new=20 >> semantics. Plus they're also more portable (on the hardware >> sense), have a look, e.g.: > ... >> So why not just use those? It seems very natural to me that if you=20 >> have something which is unambigous and reliable, you use this >> instead of something else which is prone to nasty errors. >=20 > bus_space(9!) is KPI and it must not be used on userland. Actually, > it only works on X86 by pure luck, e.g., bus_space_tag_t is an > integral type, it has very simple instructions to directly access I/O > space, etc. There's nothing preventing a bus_space implementation in user space. = It's just that we don't have one yet, except on x86 where it works by = luck. On most architectures other than x86, however, it would likely be tricky = to implement. Warner
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