Re: [TUHS] Device special files

On Wed, 07 Feb 2018 12:48:35 +1100 Dave Horsfall &lt;dave(a)horsfall.org&gt; wrote: Dave Horsfall writes: In the old days where a limited types of devices were available for a particular kind of machine, they could be statically assigned a major dev number (matching their index in the {b,c}devsw table). To make them accessible to users you did mknod <name> <b or c> <major> <minor> Usually via /dev/MAKEDEV. But this soon fell apart on PCs where you any number of devices can be attached. Even on Fortune Systems (pre PC) the system had an IO bus and static assignments listing out every possible device would've needed a lot of inodes. Recall that on a floppy space taken by each inode matters so we had to find a way! IIRC, the kernel essentially returned a list of mknod commands which was then run at boot time. So the point of devfs is to avoid having to do mknod manually and yet provide access to all found devices from the userland. As a side effect you can also use it for programs that run in their own sandbox or for jails and require access to a device.