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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