Date: Fri, 15 Mar 1996 14:25:10 -0700 From: Sean Kelly <kelly@fsl.noaa.gov> To: brian@filoli.com Cc: questions@freebsd.org Subject: Re: basic questions Message-ID: <9603152125.AA24060@fslg8.fsl.noaa.gov> In-Reply-To: <Pine.SUN.3.91.960315112614.6753B-100000@sundial.filoli.com> (message from Brian Queen on Fri, 15 Mar 1996 11:31:11 -0800 (PST))
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>>>>> "Brian" == Brian Queen <brian@filoli.com> writes:
Brian> What is the link - or where is it specified - between the
Brian> devices probed at boot, and the devices in /dev?
There is none except the hand of the system admin occasionally running
the MAKEDEV script or the rm command. The core team is working on
something called `devfs' which (I'm lead to believe) enables device
drivers to make their own entries in /dev dynamically. This is the
SMART way to go and I'm surprised other Unixes haven't implemented
similar technology.
Brian> In particular simple examples like sio0 to cuaa0 ...
Well, the name of /dev/cuaa0 doesn't matter, the device number (28)
does matter. I/O operations on /dev/cuaa0 are mapped by the kernel
through something called the device switch into function calls in the
device driver (the sio driver in the case of 28). When you build a
kernel, each device driver gets an entry in the switch with a
preassigned number. After booting the kernel, you run MAKEDEV or
mknod to build the software interface for those devices:
/dev/<whatever>.
--
Sean Kelly
NOAA Forecast Systems Laboratory kelly@fsl.noaa.gov
Boulder Colorado USA http://www-sdd.fsl.noaa.gov/~kelly/
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