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0 pointsAceJohnny27y ago0 comments

I also liked QNX, when I worked with it.

You really did access devices through the /dev/ system, and device-drivers were userspace programs that created files in /dev/.

If your driver crashed, you could kill the userspace driver (which deleted the file under /dev) and restart it (assuming hardware blah blah blah).

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Someone7y ago

”device-drivers were userspace programs that created files in /dev/. If your driver crashed, you could kill the userspace driver (which deleted the file under /dev)”

I think that shows not everything is a file. If everything were, you would start the driver by creating the file (say as a hard link from a file in /dev to the driver executable) and kill the driver by rm-ing the file.

(Chances are that, if you follow this through, this idea won’t support everything we want to do with drivers, but if so, that’s an indication that “everything is a file” doesn’t work)

zapita7y ago

To give you a sense of how far Plan9 took the idea... To open a tcp connection, you create a special “control file” at `/net/tcp/ctl` or some similar path, then write newline-terminated text commands to the file descriptor. That descriptor now represents your socket. You can also browse its contents as a directory (in plan9 each node in the filesystem can be both a regular file and a parent directory).

AceJohnny2OP7y ago

Great point.

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