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    SubjectRe: [patch 09/28] Input: convert net/bluetooth to dynamic input_dev allocation
    On 9/15/05, Vojtech Pavlik <vojtech@suse.cz> 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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