Is it possible that one device belongs to several classes?
No.
Oops, well yes. Depends on what you are thinking is a "device" here.
In the kernel, yes, a 'struct device' on a bus can then register itself
with multiple subsystems that handle different classes, and then
individual 'struct device' are created for those classes that have a
parent of the original 'struct device' on the bus.
But within a 'struct class', there can only be one "struct device" for
that class for that specific class type (we used to call them "struct
class_device" but that got removed a long time ago as the objects really
all did the same thing.)
Oki, thanks for explaining
It's a bit confusing, yes, sorry, but creating a unified object model of
all devices in the system turns out to be complex due to the huge range
of devices that an operating system needs to manage, which is probably
why most other operating systems have never attempted to do such a
thing.
From what I've heard Windows has tried the same with WDF but it's so
abstract and elegant it only plays with the "nice" devices so only
around 50%, for all other devices you still need the old device model.
So in the end every driver developer has to learn both models :D
When Pat and I created it, we were young and naive and thought "this
should be simple!" Famous last words...
:D
thanks,
greg k-h
Thank you!,
Richard
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