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SubjectRe: [patch 09/28] Input: convert net/bluetooth to dynamic input_dev allocation
On 9/15/05, Vojtech Pavlik <> 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 ;)

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