From owner-freebsd-questions Fri Mar 15 13:25:06 1996 Return-Path: owner-questions Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id NAA02272 for questions-outgoing; Fri, 15 Mar 1996 13:25:06 -0800 (PST) Received: from fslg8.fsl.noaa.gov (fslg8.fsl.noaa.gov [137.75.131.171]) by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id NAA02262 for ; Fri, 15 Mar 1996 13:25:01 -0800 (PST) Received: by fslg8.fsl.noaa.gov (5.57/Ultrix3.0-C) id AA24060; Fri, 15 Mar 96 21:25:00 GMT Message-Id: <9603152125.AA24060@fslg8.fsl.noaa.gov> Received: by emu.fsl.noaa.gov (1.40.112.3/16.2) id AA253695110; Fri, 15 Mar 1996 14:25:10 -0700 Date: Fri, 15 Mar 1996 14:25:10 -0700 From: Sean Kelly To: brian@filoli.com Cc: questions@freebsd.org In-Reply-To: (message from Brian Queen on Fri, 15 Mar 1996 11:31:11 -0800 (PST)) Subject: Re: basic questions Sender: owner-questions@freebsd.org X-Loop: FreeBSD.org Precedence: bulk >>>>> "Brian" == Brian Queen 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/. -- Sean Kelly NOAA Forecast Systems Laboratory kelly@fsl.noaa.gov Boulder Colorado USA http://www-sdd.fsl.noaa.gov/~kelly/