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SubjectRe: Migrating to larger numbers
Stephen Frost writes:
> Hmm, I think maybe the question is, which way is it driven?
> Does the kernel automagically load the driver when the device is
> detected, or does the user attempt to access a device, which the kernel
> then has to go out and see if it exists (And if it can load a module
> for it). I've seen it both ways.
> If the kernel detects it, then having a user-space daemon
> running that handles the modprobe or whatnot and the creation of the
> devices will work (pcmcia seems to work in this way). However, what
> about devices that exist at all times in a system, but are compiled by
> the user as modules to perhaps save memory? Or the issue with printers
> and zip drives, where IIRC the user can rmmod and insmod the appropriate
> modules depending on which device he wants to talk to.
> I don't know if devfs handles all of these or not, I'm just
> trying to bring up points where it would be nice to have something that
> handles these different situations, and handles them in One way (if at
> all possible) to make it easier for the user.

Devfs handles it both ways. In the former case, a device driver
registers device entries with devfs. So that can happen in response to
a device plug/unplug event, and doesn't even need interaction from
user space.

In the latter case, an attempt to access a device node for which there
is no loaded driver (and thus no entry in devfs) generates a module
load. That module load will in turn result in the appropriate device
entry being registered and magically appearing. So it all just works.



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