On 9/15/05, Vojtech Pavlik <[email protected]> wrote:
> On Thu, Sep 15, 2005 at 02:22:34PM -0500, Dmitry Torokhov wrote:
> > They are devices - class devices :). I have the following distinction
> > in my head - "normal" devices (bus devices) are real hardware devices
> > and their drivers need to do resource and/or power management. Class
> > devices represent virtual devices - some kind of abstraction - that
> > unify and combine "real" devices from several buses into one class.
>
> Yes. While input drivers do need to care about power management usually,
> the input device abstraction itself doesn't have to, which makes it
> indeed a special kind of a device.
>
Right. They just signal to underlying hardware driver when they are in
use (open), but the actual power management is left to the specific
bus/driver, not input core.
> I was always wondering whether the distinction between bus/class was
> needed, as the border isn't very clear.
>
Classes combine devices which are logically the same, i.e. they
perform similar functions. Buses combine devices that are perform
different functions but have similar hardware interface. For example a
network cards - it is a class. You can have network card sit on a PCI,
USB, ISA buses but for the rest of the kernel they are accesses
through netdev abstraction. At least this is my understanding of our
device model ;)
--
Dmitry
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