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Device Instances, Properties, and Configuration Files
(cont)
Attach Ordering:
- A driver should not make any assumptions about:
- Order of calls to attach(9E) for different instances
- Order of calls to probe(9E) and attach(9E) for different instances
- Number of times probe(9E) may be called for an instance
- Number of times attach/detach pairs may be called for an instance
detach(9E):
- Driver's detach(9E) routine is called to undo a previous
attach(9E)
- detach(9E) routine must deallocate all resources allocated
in attach(9E)
- e.g. interrupts, mutex and condition variables, device mappings, soft state structure, minor device nodes
- Driver may not retain any state for device instance
after detach(9E) returns
- detach(9E) may not return while driver has callback
functions pending
- Pending callbacks must be cancelled, or waited for
- Otherwise callback could occur after the driver is
unloaded!
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