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Date:      Mon, 14 Jan 2008 15:47:26 +0000
From:      "Igor Mozolevsky" <igor@hybrid-lab.co.uk>
To:        "Csaba Henk" <csaba-ml@creo.hu>
Cc:        freebsd-current@freebsd.org
Subject:   Re: RFC: Adding a hw.features[2] sysctl
Message-ID:  <a2b6592c0801140747r2a7ec1e5q7cd858065399ae65@mail.gmail.com>
In-Reply-To: <slrnfomt3j.i6j.csaba-ml@beastie.creo.hu>
References:  <1200197787.67286.13.camel@shumai.marcuscom.com> <20080113182457.GN929@server.vk2pj.dyndns.org> <a2b6592c0801131721w25afae5bg3dcf6a90c1a3d2b7@mail.gmail.com> <200801141254.20400.doconnor@gsoft.com.au> <a2b6592c0801131838jcde3634le6087d2f784adcbc@mail.gmail.com> <478AE741.1000105@comcast.net> <a2b6592c0801140139v42bb6ab2s667ebceb9ba3ab16@mail.gmail.com> <slrnfomt3j.i6j.csaba-ml@beastie.creo.hu>

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On 14/01/2008, Csaba Henk <csaba-ml@creo.hu> wrote:
> On 2008-01-14, Igor Mozolevsky <igor@hybrid-lab.co.uk> wrote:
> > On 14/01/2008, Nathan Lay <nslay@comcast.net> wrote:
> >
> >>  cat'ing /dev/cpuinfo sounds reminiscent to Linux /proc.
> >
> > No it doesn't - it's a perfectly fine Unix way of doing things... The
> > purpose of /dev is to provide an interface to the devices on the
> > machine, (query-capable-)CPU is a device... Having /proc as an
> > interface to the kernel on the other hand...
>
> Hm, I just fail to see the how the ioctl interface is different from
> the sysctl interface in terms of semantic capabilites.

You need to *define* the output of a sysctl, you don't have to produce
any output in ioctl, just a boolean reply or a mask that can be
processed with #define macros... I honestly don't see how all of that
can be abstracted away in a MIB given that there is a number of
Intel|AMD|Whoever feature/feature1, who knows when feature2 will be
needed...

If it can be done reasonably in a MIB, I won't say a word, but
nobody's proposed any data representation for a (or a number of)
MIB(s) yet...

What's the overhead of sysctl vs ioctl?

Igor



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