per-device sysctls

[John Baldwin]

On Friday 27 February 2004 07:16 am, Bruce Evans wrote:
> On Thu, 26 Feb 2004, Dag-Erling [iso-8859-1] Smørgrav wrote:
> > "M. Warner Losh" <imp at bsdimp.com> writes:
> > > How is this different than the sysctl stuff that already exsists for
> > > 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-bus) 
and UNIX file devices (entries in /dev).  You can ioctl the latter, but not 
necessarily the former.

-- 
John Baldwin <john at baldwin.cx>  <><  http://www.baldwin.cx/~john/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org