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SubjectRe: devfs vs udev, thoughts from a devfs user
On Wed, Feb 11, 2004 at 10:44:10AM +0100, Helge Hafting wrote:
> Sure. Completely random device numbers will make this demand loading of
> device drivers impossible. Either it won't happen (all numbers won't be
> completely random, although they may get more dynamic than today) or
> module loading based on device node opening will be deprecated.

It could be made to work. You could have a magic device number, say
(255,255), which means "unloaded device driver", which causes a
hotplug callout, and a SIGSTOP sent to the process that tried the
open. The userspace program would then be responsible for loading the
relevant device driver, converting the /dev file to the correct
dynamic major/minor number, and then sending a SIGCONT to the process,
which would then either restart the open() or the open() would return

It would be kinda hairy, in that the kernel would need to know whether
or not userspace had accepted responsibility for handling these calls
(if it didn't open() would just return -ENODEV as it does today). So
it might not be worth doing, but if people really cared about it, it
could indeed be done.

- Ted
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