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Date: Sat, 28 Feb 2004 22:09:58 +1100 (EST)
From: Bruce Evans <bde@zeta.org.au>
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To: John Baldwin <john@baldwin.cx>
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cc: Dag-Erling =?iso-8859-1?q?Sm=F8rgrav?= <des@des.no>
Subject: Re: per-device sysctls
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On Fri, 27 Feb 2004, John Baldwin wrote:

> On Friday 27 February 2004 07:16 am, Bruce Evans wrote:
> > On Thu, 26 Feb 2004, Dag-Erling [iso-8859-1] Sm=F8rgrav wrote:
> > > "M. Warner Losh" <imp@bsdimp.com> writes:
> > > > How is this different than the sysctl stuff that already exsists fo=
r
> > > > this and is accessed by devinfo?
> > >
> > >  1) it is immensely easier to access
> > >
> > >  2) it gives drivers a well-defined place to put their per-device
> > >     sysctl variables - devinfo doesn't address that issue at all
> >
> > Only broken drivers use sysctl variables.  ioctl(3) is a much better
> > interface that sysctl(3) for accessing per-device info.  sysctl(8) is
> > a better interface than ioctl(8) for handling the few device control
> > things that can be done in a generic way, but this is only because
> > there are so few such things that ioctl(8) doesn't exist.
>
> Note that ioctl's act on dev_t devices, not on device_t devices.  We have=
 two
> distinct notions of a device right now: physical hardware devices (new-bu=
s)
> and UNIX file devices (entries in /dev).  You can ioctl the latter, but n=
ot
> necessarily the former.

I think (2) means dev_t devices.  I agree that a separate mechanism (but no=
t
2) is needed for device_t devices.

Bruce